Truck with multiple personality disorder

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  #1  
Old 03-12-14, 10:01 PM
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Truck with multiple personality disorder

Nice thread title, huh?

So I'm tinkering with my 2002 F150 4.2L manual 5 speed. The main reason is that it's intermittently doing some weird things.

Some of the things it will do from time to time for some unknown reason:

-Idles pretty fast. about 1400 RPMs when cold... generally about 1200 when warm. But occasionally it will idle smoothly, around 800 to 900 which I would assume is more normal.

-The thing it has liked to do lately... meaning once every few days... is the engine surges when I push in the clutch to shift... or when you push in the clutch to stop at a stop sign. The RPMs will sometimes go up to 2400... and stay there for about 5 seconds, before slowly quieting back down to 1200 or so. (I suspect the IAC) This is probably my biggest annoyance currently, and I'd like to figure it out. So if you have any suggestions, I'm all ears.

-The intake vacuum is usually running steady at about 20 in-Hg. (when the idle is fast- 1200-1400 or so) But once when I was working on it and it was idling normally at 800-900, it all the sudden started surging, and the RPM's started to fluctuate by about 100 RPMs and the vacuum pressure dropped to a steady 15. (suspecting the coolant temperature got to a certain point and the computer mistakenly triggered the EGR duty cycle, which about wanted to kill the engine.) But it only did that once that I know of.

Of course, it's never handy to test it when driving and it's doing this... or else I'd unplug the IAC power or unplug the EGR vacuum to see if it makes a difference. Course sometimes I don't think of that until later.

It's throwing the P0171 and P0174 lean codes from time to time, which usually you would suspect a post MAF vacuum leak. (of course, the MAF could be messed up too, despite having cleaned it several times) If I clear the codes, I can sometimes drive it for a couple days before it will throw the code again. City driving seems to do it (more deceleration more often?) If it's all highway driving, it seems to not throw the lean code, at least not until I get to the city...

My B1 & B2 Fuel Trim is pretty high (>+30 or +40) when the engine is cold at idle, and at low RPMs, and maybe that's partly normal, partly the computer overreacting to the lean codes. They are very good on the highway when the engine is warm. (ranging from -3 to +3)

It also from time to time throws a P1131 and P1151 code (Lack of HO2S-21 Switch, Sensor Indicates Lean) which could also be a stuck or leaking EGR (which would explain the very low 15 in-Hg vacuum and surging). I need to do a leak test on the EGR but don't have a hand vacuum yet.

I'd like to check fuel pressure soon to rule that (and the fuel filter) out as a problem. I've gone over the vacuum hoses with a fine tooth comb, and have replaced anything even remotely suspicious. I probably need to have a mechanic perform a smoke test to be sure and rule out a vacuum leak.

The O2 sensors seem to read okay on the OBD-II Live Data graphs. The ones before the C/C range from .1 to .7 and the ones after the C/C are usually a steady .5-.6 on the highway.

MAF ranges from .01 to .12 from cold start to highway driving. Not totally sure what's normal. Anyone know?
 
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Old 03-13-14, 03:26 AM
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Does it have a pcv valve? It is the only thing you haven't mentioned that affects idling. EGR comes to mind on my older F150. Tried cleaning it, but finally popped for a new one, cleaned the EGR intake of carbon build up and it worked fine.
 
  #3  
Old 03-13-14, 08:17 AM
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When I got one acting in similar matter, I looked for problems with GROUND wires. 95%+ times a bad ground was discovered that when repaired cured the "multiple personality disorder.
Good Luck!

RR
 
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Old 03-13-14, 08:43 AM
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From my experience I would say EGR... Check to see if its clogged up...

Last would be the intake manifold leaking somewhere..I had a pontiac do this surging as you state. and the aluminum had a crack at one of the bolts. Especially on de-acceleration.
 
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Old 03-13-14, 05:02 PM
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It does, although it's not where you would think it would be. Driver's side valve cover has an elbow and a 3/8" tube that leads to the air cleaner plenum right before the throttle plate. Passenger side valve cover has a larger diameter elbow, a short length of hose, a metal pipe and another short length of hose that leads to the PCV valve (heated with coolant hoses) that is on the passenger side of the throttle body right (port is on the intake side of the throttle plate.) All the hoses were pretty loose so I changed them out. Took the PCV off and cleaned it, seemed fine, not very dirty at all. (course I did just clean the inside of throttle body some days ago with a toothbrush and spray cleaner)

So it is keeping up the multiple personality disorder. I have determined that [usually] when it is cold, it idles fast, and the OBD-II Short Fuel Trim #'s are pretty high at idle until I get down the highway, then it will eventually drop down closer to -3 / +3 after a few miles and it warms up. But once it is warm if I shut it off and restart it, it will usually idle normally, and the OBD-II Short Fuel Trim #'s are nice and normal close to (-3 / +3).

It is still doing the revving thing when I push in the clutch.... RPM's go up... and sometimes it stays up until I let the clutch out again... sometimes it will take about 7-10 seconds and it will idle down on its own. I just don't get it.

I did have the EGR off and cleaned it along with the port. One resource I found online showed how to remove the intake plenums and you will often find clogged egr orifaces there as well. Not sure I have time to go that deep into it.

It was pretty oily/dirty on the valve cover in back on the passenger side, so maybe there is some sort of leak back there. Or maybe I need new grommets for the PCV elbows in the valve cover. I cleaned off what I could, maybe I'll keep an eye on it and see how quickly it gets dirty again. Seems like an odd place for oil to be. My rear main seal does leak pretty bad (thanks, Ford dealership!) but I don't know how it could possibly get all the way up on the valve cover.

One of the things I want to try next is to replace the fuel filter. I've never done it in over 130,000 miles and I guess it can cause low fuel pressure, according to the troubleshooting from the P0171 and P0174 codes. Also I realized I never followed the vacuum lines back to the charcoal canister which is under the vehicle near the gas tank. Maybe this weekend I'll have some time.
 
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Old 03-13-14, 06:05 PM
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Very conservatively, spray ether around the intake manifold and hose entrance points. If you get a rev, then you have a leak. Sort of a pig in a poke way of doing it, but it looks like a vacuum leak somewhere.
 
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Old 03-13-14, 08:48 PM
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Yes, Larry, I've tried that with carb cleaner. But came up with nothing. But I haven't tried propane, which is what one site suggested. So I may try that again.

Mike... I have had the EGR off twice... the 2nd time was to put a new gasket on it and double check that it is opening and closing and not sticking... so as to rule that out. The port was pretty clean... just light perimeter carbon. This truck drives 99% highway miles so I suspect that has helped it burn pretty clean. I was going to run a pressure test on the EGR valve, but the hand pump I borrowed from Advance Auto is broken. (yeah thanks for lending me the broken one.) The electronics on all the other emissions controls that affect the EGR seem to check out, but I guess I didn't compare cold electrical readings with hot electrical readings, which I should do sometime soon.

I wonder about the intake manifold too... the intake plenums on this engine are plastic and I have read that the isolator bolts (Replacement Part Dorman # 55164) are prone to getting hard and brittle which could affect the bolt tension and the seal of the intake manifold gasket. Not sure about that one. But it *is* oily on the passenger side... There is a nice website with play by play pictures of the entire process. If I ever get a few days off I might try it just for kicks.

Rough Rooster... where would I look for these ground wires? Are you saying to backprobe every emission component that has a ground? and check for ground continuity? Or just the main grounds, at the battery, solenoid, frame, etc? I could see the oxygen sensors especially being subject to a lot of corrosion from road salts and such...

Speaking of that, I haven't examined the exhaust for any leaks that could be fouling up the voltage from the O2 sensors. Also haven't dropped the C/C to see if back pressure has anything to do with it.

I also wonder in the back of my mind if the ECM is starting to go on the fritz. What are the symptoms of that?

A year or more ago, the digital thermometer above the mirror quit and every once in a while the 2 far right radio buttons don't work. Then the next time I start the truck they will work. A long time ago my door bell would ding ding ding constantly when I started the truck (like the door was still open) and would never quit unless I shut it off and restarted it. But that has since fixed itself. I assume this is all unrelated stuff.
 
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Old 03-13-14, 09:10 PM
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Rough Rooster... where would I look for these ground wires? Are you saying to backprobe every emission component that has a ground? and check for ground continuity? Or just the main grounds, at the battery, solenoid, frame, etc? I could see the oxygen sensors especially being subject to a lot of corrosion from road salts and such...
They are hidden all around on the engine and fenders. Look for one or more black wires under a bolt on engine or fenders. Loosen bolt and retighten to renew electrical contact. Be sure to check for a good connection from - bat cable to a spot on fender or header along with a good connection to engine.
Had a V6 Ranger once that nearly ate my sack lunch. Finally moved AC hoses and engine ran fine. Close checking revealed the ECM wiring harness was on top of AC hose and had vibrated through insulation and the AC hose was shorting some wires together and giving the ECM erroneous readings. Taped everything up and used plastic wire ties to keep harness off AC hoses. Pickup ran great for next several years. Just one of my many shop memories of a "tough one".
You being in winter salt country does not help a bit.

RR
 
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Old 03-13-14, 09:18 PM
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Here is your problem...

2002 F150

[ATTACH=CONFIG]28315[/ATTACH]




LOL.. Just in fun!!!
 
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Old 03-13-14, 09:50 PM
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Thanks Rough Rooster, I will check that out as well. Bought myself a nice Klein Multimeter the other day so I'll do some looking and testing. You are right about the salt up here. It's insane... anytime it even thinks of snowing they spray that liquid salt on the roads and it turns my dark blue truck white. It's eating my truck alive.

LOL @ Mike.
 
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Old 03-14-14, 07:32 AM
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XSleeper,

Read this blog for enlightenment on grounding problems.

Design News - Made by Monkeys - Check Memo for Intermittent Electronic Problems

This exemplifies problems associated with poor grounds.

RR
 
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Old 03-14-14, 04:58 PM
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Thank you for the link, I'll check it out!
 
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Old 03-14-14, 10:16 PM
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Well there are a lot of things that I haven't ruled out yet, but after watching the OBD-II diagnostic "live data" all this week and after messing with it some more tonight, watching it idle, watching the vacuum pressure and idle speed and fuel trims...

The codes the truck originally threw were P0171 and P0174 (lean). This often means a vacuum leak. If the lean condition goes away at higher RPM's (which mine does) it also would seem to indicate a vacuum leak. But I found something out tonight that might change all that, and cause me to look somewhere else:

I have realized that a lot of the "multiple personality problems" and irregular idle are somehow related to the computer switching from "Open Loop" to "Closed Loop".

At Idle, my fuel trims will run very high (rich) for a while.... then it's like a switch flips (to open loop) and the fuel trim will immediately get lower (lean). This affects the engine RPM's, the engine vacuum and probably other things I'm not aware of. It also explains why the truck seems to run so much differently when it's warm vs when it's cold.

I don't think any of the fuel trim and idle problems have anything to do with vacuum leaks, the EGR, or control modules like the IAC or the TPS.

I'm just now considering how this all relates to my O2 sensors. (primarily B1S1 and B2S1). I've always been of the opinion that replacing O2 sensors is usually a waste of $$$, and that it's something mechanics love to do since it "might" be the problem. So while I'm not a big fan of just replacing things without testing them... I guess I'm just like one of "those" mechanics. So I'm kind of leaning toward replacing both front 02 sensors and see what that does. I know they haven't been replaced in at least 150,000 miles and that they are very important in helping the PCM balance between rich/lean, so I can't see how it could hurt to put new ones on. Every now and then I will get a temporary code that indicates an O2 problem, but it has never thrown a permanent code. And they obviously still work once the exhaust gets to 600°, because the live data shows the variable voltage signal they are sending. But maybe the heating element isn't activating them as soon as it could... or maybe they're plugged or corroded and aren't sniffing the air like they should.

I also realized that I don't have an adapter to go from my vacuum/fuel pressure gauge to my Schraeder valve. So I'll have to pick up some sort of adapter in order to test my fuel pressure. I'll do that when I pick up the 02 sensors and fuel filter. I'd like to test fuel pressure before and after the fuel filter just for kicks.
 
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Old 03-16-14, 07:38 PM
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Well, worked on the truck this afternoon... I didn't get to check the fuel pressure like I wanted to... I forgot to get a clamp to keep the pressure gauge hose on my adapter, so when I started the truck it blew the hose off and sprayed fuel all over the place. LOL That could have been bad! (Lesson learned) So I just changed the fuel filter without checking pressure before/after and would have to say that the new filter has GOT to make a huge difference. The old filter drained dark brown fuel out the back and a lot of tiny rust chips. Who knows how long that filter has been on there! Now that I know how simple it is, I'll do that more often. (Chilton's says every 15,000 mi or annually)

Also changed the front O2 sensors that are on the back of the exhaust manifold. That was a real pain! Only room for a short ratchet in there and short ratchet = no leverage! The 7/8" O2 sensor socket I bought was a P.O.S. as well. Had to grind the inside with a grinder to remove burrs to even get it to fit over the sensor... and it still wanted to slip over and round the nut. Ended up giving up on that, clipped the top of the O2 sensor off with a grinder so that I could use a normal socket. That was still tough but finally managed to get it off. Using a torch on the manifold didn't seem to help much.

Also took the airbag off and changed my cruise control switches. (trying to diagnose why it hasn't worked for years) but all I've managed to figure out is that the new switch works. Lights up with the headlights now and all the ohmmeter readings are within specs at the cruise servo harness when the corresponding buttons are being pushed. Next thing I will test will probably be the brake pedal position switch and the clutch pedal position switch. And maybe the vehicle speed sensor. Hope it's something simple.

Drove it around a little today and it seemed to run good. It still does run a little differently when the PCM switches between OL and CL... OL-Fault and CL-Fault and OL-Drive. But I suppose that is somewhat normal. Fuel trim % is high at idle under certain switch conditions... but at other times the fuel trim % will be low which is where I think it should normally be most of the time.

I still don't think it should idle so high when I push the clutch in.
 
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Old 03-16-14, 08:33 PM
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disconnect the idle air control valve and drive it around...Tell us if the high idle goes away... If its not a vacuum leak this would be the next thing IMO.
 
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Old 03-17-14, 02:26 PM
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Nothing like a challenge to keep a guy on his toes!

Forgive me if i mention something already discussed or miss something, lots of info in all the posts, and i have a short attention span lol

Is the problem only happening at idle? How does it run going down the road, any surging at cruise, loss of power?

A couple of things come to mind, first is the IAC, 800-900 rpm is too high, and as lawrosa said, you can disconnect it and see if it stops surging. The idle should be lower than normal with it disconnected, and no surging, you may have to give it just a little throttle to keep it running. If it doesn't change and the idle is high the IAC could be stuck partially open, remove it and block off the passages - you should get a lower than normal idle with out the surging.

Another is the MAF sensor, the get dirty and sometimes get stray pieces of air cleaner material on the hot wire and it screws up the readings to the PCM.

Most lean codes that are caused by a vacuum leak will be one bank or the other rather than setting both banks at the same time... except for maybe a leak in a hose that feeds both runners in the intake manifold.

If the MAF is dirty the PCM thinks there is ess air coming in and changes fuel delivery accordingly. The result is both banks are lean, P0171 $ P0174, sometimes O2 codes also.

EGR will not cause surging at idle, it will run rough instead and never causes lean codes - EGR flow richens the mixture by displacing oxygen in the cyls.

Another thing is BARO, it is part of the MAF sensor, since you have access to live data stream, check BARO, and clean the MAF (I like seafoam spray).

At this point I would suggest you clean the MAF, and check BARO, it should be about 159 hz at sea level, deduct 3 hz for ever 1,000 feet above sea level - if after cleaning it, it is wrong, replace it.

You could have multiple problems, which is always difficult, it is sometimes a process of elimination, and as you said its better to test than throw parts but sometimes test are inconclusive or impractical compared to the cost of a new sensor like an O2 on a high mileage vehicle. As a ***** I know this all to well ... "take two of these and call me in the morning" sometimes applies in the automotive world too

Good luck!
 

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Old 03-17-14, 05:44 PM
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Thank you for your input mobilemechanic.

Just to bring you up to speed here is a synopsis:

First thing I did when I got my OBD-II scanner was clear the codes. It was missing and doing other odd things so I wanted a clean slate to start diagnosing things. (check engine light had been on for years).

The first codes it threw was the lean codes P0171 and P0174. I fixed the ignition miss by replacing the coil. I did plugs and wires too while I was at it, since it was time.

However it was still throwing lean codes P0171 and P0174. By this time it was also throwing O2 codes P1131 and P1151.

So I did a number of things:

-removed / cleaned the throttle body
-removed / cleaned the MAF
-removed / cleaned the EGR
-removed / cleaned the IAC
-removed / cleaned the PCV
-removed / cleaned the TPS

I also tested the voltage and resistance of the above devices and a few more that are electrical... all OK.

I have scoured the engine for vacuum leaks... and replaced a few suspicious hoses. Lastly, I replaced the fuel filter (filthy with bits of dark, rusty fuel coming out the back) and the O2 sensors.

Everything I have done thus far has made some improvement, but after replacing the fuel filter and O2 sensors, it drives a LOT better. After driving about 140 miles thus far, it has not thrown any codes yet. It also switches to CL (closed loop) much faster now that the O2 sensors are new. I'm guessing the old ones were fried and weren't heating up fast enough upon cold starting.

As for the idle... it still idles a little fast (between 900 and 1100) and when I'm driving down the road (lets say 30mph at 1200 rpms in 4th gear) and slow down and I push the clutch in to shift... the RPMs will immediately jump up to about 1700, which I think is a little odd. It sometimes stays high (around 1500) and other times it will slow down after about 7 seconds (to around 1100, which still seems high).

I would like to unplug the IAC as was suggested... but not just yet since it will throw a code. I want to see if I can drive it all week and not have any codes thrown. However, if it is sticking open, just disconnecting it may not prove anything. The couple times I have removed it, it has always been closed. However, if I remove the brake booster vacuum line to hook up a vacuum gauge to the intake manifold, I will get a P1506 code, which is normal for it to detect that from what I can see. (vacuum is a steady 20 in-Hg)

In answer to your questions, it now drives fine on the road, no surging, no power loss. My truck does not have a BARO, but it does have an IAT sensor that is working fine. The ECT sensor is also reporting accurately.

I've run 5oz of Seafoam into the intake manifold on two occasions, and put a 16 oz can of it in the fuel tank. I think my problems are close to being over.
 
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Old 03-17-14, 10:23 PM
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There are two switches for the clucth tpp/ One is the neutral and the other is for the computer I think... Ummm.. Look that up and see what you find. It may be related... Does your gas mileage stink as of lately? I would change the EGR is so... Possibly its not closing?

I have to re read everything here...

Where is the canister? Is the vacuum hose to that good? Leaking?
 

Last edited by lawrosa; 03-18-14 at 05:41 AM.
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Old 03-18-14, 04:55 AM
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There is one Clutch pedal position switch (manual trans). Gas mileage was bad (got 350 miles per tank instead of 400) but I haven't used a full tank since the repairs so we will see. The EVAP canister is back by the gas tank. Already tried to trace those vacuum lines and didn't find anything unusual. Most of the hoses are metal fuel line with a few vacuum hose couplings.
 
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Old 03-18-14, 05:44 AM
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There is one Clutch pedal position switch (manual trans).
I think there are two... Unplug the one that is not for the nuetral and try that...


The EVAP canister is back by the gas tank.
Yes thats the common leaker I believe..... You can disconnect one and and maybe test with your pump...
 
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Old 03-18-14, 06:01 AM
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The Chiltons and the electrical diagram show one switch but i will look. It acts the same whether I coast with the clutch in or if I just drop it out of gear (not using clutch) so I doubt its a clutch switch.
 
  #22  
Old 03-24-14, 06:24 PM
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Dear XSleeper, I have a FORD F150 2002 4.2 L (It was built in Venezuela factory) with the same problem you have, I try all the sugestions made in this thread but nothing solved the problem, I can add a weird thing also, I connected an scanner to the power socket beneath the radio but no power on it, after run for a while the power come back to the socket it seems like this power socket runs only when the engine is hot, but itīs not so because it some times the power goes off and come back randomly, I tested it conecting a light bulb to see when it lights, probably could be a ground problem, but I still donīt find the cause of this but I still think the problem could be the IAC sensor
I apreciate very much your help if you find the answere to the RPMīs problem
 
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Old 03-24-14, 08:07 PM
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When the clutch is depressed and the RPMs increase it tells me that the clutch's signal to the ECM is either not getting translated properly for the IACV, or more likely, the IACV is faulty. Considering the age of the truck, rather than spend any more time testing it, I would just go ahead and replace it.
 
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Old 03-24-14, 08:09 PM
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Hi Castro and Bigfred,

I also thought it would be the IAC. I actually made a cardboard lid (gasket) to eliminate ANY air passing through the IAC, and put it back on. It idled MUCH lower. So I thought that clinches it, it must be the IAC valve! Wrong. Replaced it and the new one does the same thing as the old one. So it's the PCM that is telling the IAC to open and let the engine run fast, based on who knows what information- supposedly it's the elusive vacuum leak that is causing all the meyhem.

So I've ordered all new gaskets and isolator bolts for the upper and lower intake plenums, along with valve cover gaskets, IMRC actuator rod bushings and fuel injector o-rings (since I'll be right there, might as well take them out and give them a bench test and a cleaning).

I've pretty much ruled out any other sort of vacuum leak... plugging the intake manifold vacuum ports does nothing to slow the idle down so my hope is that the isolator bolts are the solution. Maybe by this weekend all the parts will be here.

Castro, as far as your power problem to the lighter... I know the connections in the lighter can be finicky. I would assume that it's just a bad connection. If you can get one of those 12V testers that looks like a sharp pointy screwdriver with a light bulb inside of it... probe the hot wire to the lighter outlet and see if it's got power 100% of the time. (I believe it is the yellow wire w/lt green stripe)

Also, does your horn work 100% of the time? When the lighter outlet doesn't work, test your horn and vis versa.

At night, is there any lighting down there in the ashtray where the lighter is? And does it work 100% of the time?
 
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Old 03-24-14, 08:37 PM
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Back to the clutch pedal position switch that you both mentioned (Mike and Bigfred), the Chilton's does say that besides being the neutral switch (no start if clutch is not depressed) that it's also "an information sensor for the PCM" that apparently controls the EGR and IAC.

I'll have to test that sometime soon. It says there should be zero resistance (0 Ω) when the clutch is pushed. Maybe there is a problem there.

And as for the cigar lighter, Castro, I see that there is one for sale on ebay right now, if it helps.
 
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Old 03-24-14, 09:02 PM
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geez...Just change the clutch switch before you do all that work... What the cost of the switch ?

Just my opinion...Worth a shot...???
 
  #27  
Old 03-24-14, 09:14 PM
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$90.......................................

 
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Old 03-25-14, 04:39 AM
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Holy crow!!!!!! Thats highway robbery...
 
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Old 03-25-14, 01:15 PM
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Thanks XSleeper, continue talking about the idle I have to tell you that the problem get worse when drive at high speed 80- 90 mph, the idle gets higher and when suddenly have to stop, the brakes doesnīt respond instantly and takes a 2 seconds to start breaking making the driving very risky, I think that is because the high idle for long time reducing the vaccumm in manifold and in the brake boost, making me think the problem in vaccumm leaks, but I dont have any diagnostic codes and everything aparently is OK.
I was also talking with an old FORD technician and he said that probably the PCM is not well configutated or it īhas a wrong configuration, I dont know if that is possible but I think you could check and see.

Best Regards

PS: please let me know how works the change of manifold isolators.
 
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Old 03-26-14, 07:08 AM
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Food for thought:
Clean the IACV bypass air passage(s)
Check the PCV grommet for cracks
Reset the ECU (disconnect battery)
Faulty clutch position sensor
Faulty throttle position sensor
 
  #31  
Old 03-26-14, 05:10 PM
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Thanks for the suggestions bigfred.

The IAC has been replaced (no change) and the passages are clean. Blocking the IAC valve ports with a solid cardboard gasket makes the engine run dramatically slower/rougher. Plugging in the old IAC valve while the truck is at idle, I can see that the valve is practically closed and barely opens at all when the throttle is snapped.

The PCV hose has all been replaced. I have not replaced the grommets yet, but I plan to when I remove the intake plenum and valve covers because they are a little loose, but not terrible. (replacing isolator bolts and all gaskets sometime soon.)

PCM has been cleared multiple times and has gone through the learning curve of idle/drive each time.

Throttle position sensor is not faulty, voltage has been checked with KOEO with a multimeter and a throttle movement test with the multimeter checks out OK. Voltage increases with throttle position and is not jumpy. Resting voltage within specs (.95 V) Live data on OBD-II scanner also reports throttle position accurately with no jumping around.

I haven't found any information as of yet as to what readings I should be getting from the clutch position sensor, but I will keep looking. I'l probably get a chance to look at it again this coming weekend.

I've also combed over the EVAP system and found nothing to report. Completely plugging the vac ports from the intake manifold makes practically no difference in the idle speed. This is why I suspect the vacuum leak is the manifold itself, hopefully at the isolator bolt gaskets. The plenum *is* plastic so I will have to look for cracks when I remove it. I guess it's not unheard of that they can also warp.
 
  #32  
Old 03-26-14, 08:32 PM
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Wow. You've got a tiger by the tail on this one. I know the feeling. But, I bet you won't quit till you tame that tiger! I figured you had done the ECM reset, but you know how it is. Sometimes we get so involved in a problem that we overlook the obvious. I'll be thinking about this and if I can think of anything else will post. But, the key is when you press the clutch, the RPMs increase. So, it must be clutch related.
 
  #33  
Old 03-29-14, 08:30 PM
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Ugh...

I am completely exhausted. Spent ALL DAY working on the truck, laying over the top of it, etc. Removed throttle, IAC, PCV, hoses, coil, wires, heat shield, upper intake plenum, middle intake plenum, valve covers, fuel rail and fuel injectors.... sprayed out fuel injectors and put new o-rings on them, and all new gaskets... and got it all back together. Was pretty pleased with myself.

Thought that at the end of the day I would be able to start it up and see if the work I did made a difference. Turned the key on, and smelled fuel. DOH!!!!


Why didn't I think to turn the key on when I had the intake plenums off, to check for leaks??? aaaaaaaaaaahhhhhhhhhhhhhhhh!

Apparently when I put the injectors back into the fuel rail I must have either knicked the o-rings or something, because 2 of them leak!!!

So I am throwing in the towel for tonight and going to bed. Just needed to vent.

On the plus side, everything else seemed to go pretty well. While cleaning the intake, I found that 5 out of 6 EGR intake ports were 99 to 100% plugged. That might make a difference! If it ever runs again, that is. Can't wait to take it all apart again tomorrow. Take two.

 
  #34  
Old 03-29-14, 09:57 PM
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Sounds familiar to me. Guess it goes with the territory. Good luck tomorrow. Sounds promising finding the EGR ports plugged.
 
  #35  
Old 03-30-14, 06:37 PM
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Well, my victory is complete!!!




Took it apart for the 2nd time this morning (went a lot faster now that I know what I'm doing. Picked up the correct tool to disconnect the 1/2" and 5/8" fuel lines from the fuel rail so that I could completely remove it (makes inserting injectors so much easier!) and found that I had pinched the o-rings on the 2 fuel injectors that were closest to the fuel lines (where I couldn't lift the fuel rail very high to remove/ reinstall them) Took them all back out to double check everything... found one bottom o-ring that had a knick in it so I replaced it again. (good thing I ordered an additional set of 4!)

Put it back together and it fired up on the first turn! I had my scanner hooked up and IMMEDIATELY could tell the difference by the lower short term fuel trim numbers (near 0% rather than at 32.8% like before) and lower idle rpms. Also previously I had almost no voltage at idle (flatline at about .3 V) being returned by the front O2 sensors (I replaced them a few weeks ago so knew they were working properly) but now I have a nice oscillating wave graph between .1 and .75 V at idle on both banks.

Not sure what the actual problem was since i did SO MUCH stuff all at one time, but I know the passenger side valve cover gasket was pretty oily which made me suspicious. The isolator bolts looked hard and brittle, and it's known to be a problem w/ this engine. The edges of other gaskets seemed to be in good shape- no signs of sucking dirty air, and all the fuel injectors seemed to check out. PCV valve has a large o-ring where it fits into the throttle body what was old and baked hard... could have been sucking air there too.

So here's a rundown of what I did:

-new intake plenum gasket set (upper & middle)
-new isolator bolts
-new valve cover gasket set w/ new valve cover bolt o-rings
-new throttle body gasket
-new pcv valve (this engine has it mounted on the throttle body, not on the valve cover)
-tested resistance of fuel injectors (.12 Ω which is good)
-sprayed about 2 oz of carb cleaner through each injector on the bench with a homemade battery/air compressor setup
-cleaned MAF sensor again (for good measure)
-cleaned oily gunk blocking EGR port orifices and blew out EGR ports inside intake manifold w/ compressed air

I'll be interested to see what my fuel mileage jumps up to. I'll also be interested to see if the performance has improved. I'll have to pass a few people on the highway and see if it's more responsive. The idle is now down where it probably should be for an engine w/ a manual transmission... around 840 rpms. And there is no more "surge" when you push the clutch in. So that's awesome.

Glad that's done! Took lots of pictures for posterity. Thanks to all who commented.
 
  #36  
Old 03-30-14, 07:21 PM
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Glad it worked out...

It was the Omega sign that flagged this post... You need to wait until a mod approves the post. No sense trying to re post...

(.12 Ω which is good)
 
  #37  
Old 04-02-14, 10:09 AM
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great thread OP, thanks for posting your process of elimination. glad you figured it out!
 
  #38  
Old 04-02-14, 07:01 PM
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Tenacity triumphs again. Good job.
 
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