Started Stalling often on Idle – 98 Nissan Frontier

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  #1  
Old 07-04-15, 01:28 PM
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Started Stalling often on Idle – 98 Nissan Frontier

Started Stalling often on Idle – 98 Nissan Frontier

I have a ’98 Nissan Frontier, 4WD, 4 cylinder, manual transmission, 150k miles.
Has run fine all its life, other than a few small leaks in coolant (fixed).

Last night, after a long 4 hr drive up here at my parent’s house, I temporarily stopped on top of the driveway to peek at my water line and the engine STALLED ON IDLE.
I restarted it and drove down 30 yards in front of the garage. I noticed it was having trouble holding idle in neutral, sometime dropping rpm below 500 RPM and then revving up, sometimes stalling. Engine sounded fine at higher RPM.

Today I started the truck to go into town. Just a mere 400 yards from the house it stalled while changing gears (it’s a stick shift). While moving, the engine would restart if I released the clutch while in gear. Then another 200 yards later I noticed a slight but sudden loss of power. That is when I decided to return home, lest I risked get stranded. I drove back the 800 or so yards and parked in front of the garage.

I tried to troubleshoot:

- It starts fine, and most of the time idles fine.

- If I rev up the engine on neutral and then let it fall back to idle, sometimes it stalls, most of the time is normal and a few times I see it begins to stall and then recovers.

- I let the engine idle in neutral without revving up for an entire 10 minutes, twice, and it never stalled.

- I drove up and down the driveway a few times and did not notice any loss of power, just the occasional stall if I stop in neutral. If it is to stall, it stalls immediately after the engine revs down from a higher RPM. I did not drive further, for fear of getting stranded on a 4th of July Saturday.

- I have no OBD codes (I read memory with simple code reader), and, of course, no check engine light.

- If I turn on the AC, the stalling becomes more frequent (logical since there is more torque at idle-but does not look like AC is the culprit).

- I moved around the spark plug wires while idling to see if I could cause any changes in idle, but it had no effect.

- I looked at the MAF (Mass airflow sensor) through the hole inside the air cleaner element, and it looks ok, I can see the two tiny heated wires in the air bypass hole, the wires seem intact and clean.

- Some posts advised disconnecting the MAF to put the computer into default operation and if that eliminated the idle stall problem then MAF may be at fault. I did not do it because if I take the truck into a shop tomorrow and there are codes or tests pending from clearing codes, I may confuse them.

I’m at my parent’s house and I need to drive back home 4 hours away. I’ll make an attempt to find a shop tomorrow Sunday see if they can help me, but I could use today to try to either fix it myself or get further ahead on narrowing down what it may be.

Any help greatly appreciated
 
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  #2  
Old 07-04-15, 02:04 PM
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Since there are no codes, I would suspect a vacuum leak or a clogged air cleaner.
 
  #3  
Old 07-04-15, 02:17 PM
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The air filter is rather clean. I do change it every 30k miles and the air where I live has very little dust. Would't a vacuum leak be constant? Why this intermittent behavior?
 
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Old 07-04-15, 02:58 PM
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What about the exhaust? Is it too white or too dark? Is the PCV clogged? I'm just thinking of the basics. I know what you are saying about it being intermittent but I would still look for a damaged vacuum hose.
 
  #5  
Old 07-04-15, 03:26 PM
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I also just looked at my spark plugs, they are not wet, but they do have more carbon deposits compared to how they once looked.

Here is a photo of how spark plugs look just now(cylinders 1,2,3,4 left to right) :


And here is how they looked in 2009:


Could this finding be related?

I will look for vacuum leaks next. But that seems like a difficult task. Most of the vacuum network is behind something else, and it’s a maze too. That is why I was trying to start from the easier probabilities.
 
  #6  
Old 07-04-15, 05:15 PM
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Those plugs are not in good shape. At least clean them with some emery cloth or sand paper if you can't get hold of a new set.
 
  #7  
Old 07-04-15, 06:20 PM
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Pulpo, thanks for confirming. I imagine the plugs in the second photo look ok (except cylinder #1 is a little darker in the older photo too – but overall ok back in 2009 right?)

The plugs are not old though. I think whatever deposits they have it’s just a symptom not the cause. The fact that they are also all equally black, probably rules out any single injector having gone bad.

I have a hunch this is something to do with the IACV (Idle Air Control Valve), AAC (Auxiliary Air Control Valve) , FICD (Fast Idle Control Device) complex of devices – though I have not figured out exactly what each one device does. I have the shop manual, I’m doing a bit of reading. I have to return home tomorrow 200 miles away, so I’m in a bit of a bind with everything closed for July 4th.

I wish I were closer to home so that I could test drive it a bit and see if there are any symptoms when the engine is not idling and is under load. But I’m afraid I’ll get stranded. I want to save my chances for driving to a shop tomorrow morning. Only one shop open in town Sunday 4th of July.

BTW, cold engine behavior with the typical faster idling is ok. So is the increase in idle RPM when the AC is turned on.
 
  #8  
Old 07-04-15, 07:55 PM
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You are right about it being the symptom & not the cause & also right about the IACV. There might be a way to clean the IACV. I don't remember. Clean the plugs enough to get home, if that's possible. If you can replace the IACV, that might be better.
 
  #9  
Old 07-06-15, 06:19 PM
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How can I start car/truck without air filter?

How can I start car/truck without air filter?

Why do I want to do that? Just trying to debug a problem. Details below.

=========================================================================

1998 Nissan Frontier, 160K miles, well maintained.

I’m trying to debug an intermittent problem with occasional stalling on idle and what one may describe as occasional engine hiccups at freeway speeds.

It is an infrequent problem, stalls one out of 20 times at stop lights, and I experienced about a dozen short engine hiccup episodes on a 250 mile trip.
So far seems to happen more in hot dry desert weather than moist cooler air, but the issue is too recent to claim a definitive connection to temperature and weather.
Even when its not stalling, the idle is often a little erratic, but not always. When erratic the RPM tends to fluctuate a bit.
No Codes

Problem happened away from home on a long trip and after attempting to debug the issue myself, I finally took my truck to the only local mechanic that was open yesterday. He run some diagnostics and told me that he was seeing a “noisy MAF sensor signal” and suspected it was the MAF connector because as he eventually showed me, when he pressed on the MAF electrical connector the engine would stall.

However he could not replace the connector because it was Sunday and the Nissan dealership was closed. He tried to improve on the contact by bending the pins a bit and inserting small wires on the contacts but was ultimately unsuccessful. He was actually a very nice guy, I wanted to pay him at least something for the 1.5 hours he spent working on my truck, even if he did not fix it, but he insisted that he did not want any money since he was unable to fix it. So I left feeling kind of bad -- I thought I should at least buy him a gift next time I go by that area (which I tend to do once a month).

But back to the truck issue…

I made it back the 200+ mile trip with a couple of stalls at idle and about a dozen short episodes of engine hiccups at freeway speed.

I think the mechanic may be more or less right in his diagnosis (he gave me the impression of being rather competent), but I also have several doubts on the electrical MAF connector being the exact cause:

a) I do not know how many times he tried to press on the MAF connector and get the stall, he only showed me once and perhaps it was also a coincidence
b) Shouldn’t the computer give me a code, perhaps not immediately, but after 300 or so miles, even an intermittent problem is likely to be cought. I disconnected the MAF myself as part of my own tests and I did get the expected P0100 code, so some error detection is working. I imagine that an intermittent connection would sooner or later stay disconnected long enough to throw a code. One hopes that even a noisy MAF signal would throw a code, but according to the mechanic Nissan is rather conservative in throwing codes, at least these somewhat older vehicles seem to be.
c) I imagine that when you futz around with an electrical contactor that has intermittent connections you either end up with good contact, or no contact at all (which should throw a code). I cannot imagine disconnecting and reconnecting a marginal electrical contact two, three, five times and always reconnecting it in that marginal semi-contact state. Especially if you also change the configuration of the pins a bit or insert a few wires to make better contact. On reconnection you end up with something better or worse. Ending up in the exact same intermittent contact condition seems possible but very unlikely.

So I suspect that what might be happening is that he is right about the MAF but that it’s the MAF itself that its faulty, not its electrical connection. Perhaps applying pressure on the contact just transfers some tension inside the MAF device itself and that is where there is a problem (electrical connection or otherwise).

In any case, now that I made it 200+ miles back home, I’d like to do some more testing myself by wiggling around cables around the throttle body, and see if I can make the engine stall. But to do that I have to run the engine without the air filter. I tried it a few times, but the unrestricted airflow makes the engine stall. Is there a trick mechanics use to start the engine without an air filter for diagnostic purposes?

P.S. This is related to my earlier post from a few days ago, but since I’m asking a different question I started a separate thread. If we find a solution I’ll post it in the other thread too.

Thanks.
 
  #10  
Old 07-06-15, 06:29 PM
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As far as starting your truck without an air filter, that shouldn't be a problem. Just don't drive where it is dusty or for very long. I'll leave the rest of the post to others.

Bud
 
  #11  
Old 07-06-15, 06:43 PM
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but that it’s the MAF itself that its faulty, not its electrical connection. Perhaps applying pressure on the contact just transfers some tension inside the MAF device itself and that is where there is a problem
Based on my experience I would agree with that 100%. If it were the actual wiring connector you should see that it's corroded or the pins on the sensor are corroded. The pins inside the plug don't normally loosen up.

I am concerned that that there was no code set. Any electrical jitter like that should set a code almost immediately. A dirty/sticking idle air control valve can cause similar problems.

I merged your threads. Having a similar problem in two threads leads to a lot of duplicate questions and wasted time.
 
  #12  
Old 07-06-15, 08:33 PM
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Any electrical jitter like that should set a code almost immediately
Indeed,... how is it possible to know how programmers implemented the MAF signal logic on a 98 Frontier computer control? Eg. whether the logic includes noisy MAF signal detection… … only if someone has somehow done similar experiments, I imagine,…

In any case, I’ll try to start the truck without the air filter assembly and see if I can recreate the faulty behavior. I tried to start like that once or twice two days ago, but it seemed to stall immediately. I did not insist out of fear I may actually damage something. I’ll give it another try this evening. Perhaps there’s a trick mechanics use to restrict the airflow to a situation similar to having an air filter in place? When the mechanic had it running without the air filter I did not pay attention at how he managed to get it running, I was just looking at his MAF contact explanation.


A dirty/sticking idle air control valve can cause similar problems.
Based on the carbon deposits on the spark plugs, it seems to run rich. Would a sticky idle air control valve cause that? I thought the idle air bypass is closed during cruising. Or, would running rich at idle only (which is what one would expect with the sticky idle air bypass) be enough to cause the spark plugs to darken?
 
  #13  
Old 07-07-15, 04:53 AM
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It would have been good to travel with a new IAC. I guess you already left.
 
  #14  
Old 07-07-15, 11:45 AM
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I was able to start engine without air filter and focused on the MAFS:

CLEANED MAFS—NO EFFECT:
I cleaned the MAFS with MAFS cleaner (it was a bit dirty after all-had to look at it with magnifying lens) -- no effect. Still stalled at about 10% of stoplights and had more hesitation and sputtering than before. ~10 episodes in a 15 mile trip.

RECREATE STALL BY FUTZING WITH MAF—NO EFFECT:
I cannot recreate the condition the mechanic showed me whereby engine was stalling by pressing on the MAFS electrical contactor. I wiggled bent pressed on the contactor and its cables, no difference, just a not so healthy idle throughout. Perhaps what the mechanic showed me was just a coincidence at the time.

TRY HOT/COLD AIR ON MAF—NO EFFECT
I alternated blowing hot and cold air on the MAF housing using a blow drier, to test my previous temperature dependence theory. Again no difference. Note: because my MAFS is right on the throttle body I had to cut a piece of cardboard to shield the MAFS air hole from the blow dryer air flow, otherwise if the blow dryer airflow gets close to the MAFS air intake it disturbs the air flow enough to confuse the MAFS and then the engine does indeed stall.

tests to be continued...
 
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Old 07-07-15, 08:00 PM
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Here is how spark plugs look today after 18 mile drive( 10mi freeway + 8mi city). About 10 short episodes of sputtering at highway speeds and two stalls at stoplights.

Do these still indicate “rich” combustion?

 
  #16  
Old 07-07-15, 10:11 PM
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They indicate running a little on the hot side but not rich. The plugs are not the problem, IMO
 
  #17  
Old 07-09-15, 05:28 PM
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NOISY / UNRELIABLE MAF SIGNAL?

I think I may actually have a noisy / unreliable MAF signal.

Look at this first video.

With the engine NOT running and the ignition on, I taped the MAF air hole at the throttle body with a piece of electrical tape (the MAF in this 98 Frontier is in the throttle body). You can actually see the black strip of electrical tape at the very top of the video.

I inserted a paper clip into the MAF signal pin (the signal that tells the computer what the airflow is) to measure the signal.

In the beginning, the signal out of the MAF is a low 0.76V. This is a low value but I have zero airflow. Not sure what the signal should be with 0 airflow (but I measured the signal at idle and it is within spec).

But now notice what happens when I press both the connector and the MAF housing. The voltage starts fluctuating, sometimes going as high as 1.30 V. I also show how striking the MAF housing makes the signal fluctuate.

I did make sure I had a good connection to the wire through the paper clip and alligator clips, to make sure I was not just measuring bad connections at the measurement apparatus.

So is this normal? Is it normal for the signal to fluctuate like that with the engine not running?

http://youtu.be/-xdD0uazA9Q
 
  #18  
Old 07-13-15, 03:09 PM
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MAF SIGNAL LOOKS NOISY ON SCOPE:

In the following video, I borrowed a potable scope to look at the MAF signal. The video shows the MAF signal while I press either on the MAF housing or the MAF connector. The engine is idling most of the time, though I do rev up in a couple of instances. You can hear the uneven idling (yes I have a noisy belt pulley too).

Other than the electrical noise the MAF signal voltage looks within specs. Per Nissan shop manual specs for MAF signal are 0.9-1.8V at idle and 1.9-2.3V at 2500rpm. As you can see in the video my idle voltage is about 1.6V at idle and 2.2V when engine is revved up.

This MAF signal looks noisy to me. I have never looked at any automotive signals with a scope before, so I don’t know what to expect. But still this much electrical noise does not look normal to me.

Anyone has experience with this?

https://www.youtube.com/watch?v=0oaSzRDEAwQ
 
  #19  
Old 07-13-15, 03:41 PM
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That's beyond my scope. Once again it shows how outdated I have become. A friend of mine was surprised when I knew what an IAC was.
 
  #20  
Old 07-25-15, 10:32 PM
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1) Five days ago, I did a crude test for VACUUM leaks:

I made some contraption with a glass jar and two hoses, lit an olive oil drenched paper towel in the jar, closed it and blew some smoke through the brake booster vacuum line.

I did not see any vacuum leaks, though, admittedly I could not make a lot of smoke this way. But seems to me I should have discovered any major leaks even with this crude device.


2) So (four days ago) I CHANGED THE MAF SENSOR:

Behavior changed, I no longer get the occasional hiccup at cruising speeds but problem with idle persists.

I did not want to buy an OEM MAFS just on suspicion (It is about $400) so I got a cheap one online for about $35, just to try it out.

On the positive side, the new MAFS does not have a noisy signal like my original. When I wiggle and apply pressure on the MAFS electrical connector or the MAFS housing with the engine not running and ignition on, the signal I read with a voltmeter stays constant. Also the new MAFS seems to respond to the engine being revved up -- the voltage increases. I have not looked at the signal with a scope but I’m pretty sure its more stable. Is it more accurate than my old MAFS? Well that I don’t know.

But in any case, with the new MAFS I don’t seem to get the short power hiccups I was experiencing before at cruising speed. I have now driven back and forth 3 times to work (6x20 miles) and no cruising speed hiccups. I used to get 4-5 hiccups per trip before.

However, the idle is still erratic when I go to work, but not when I return! Also, I never get an erratic idle immediately. Certainly not when the engine is warming up (fast idle). But even after the engine reaches operating temperature, still the idle is normal, in the beginning. Then, going to work, after I have driven a good 20’-25’ on the freeway and then continue on city traffic THEN I notice the rough idle at stoplights. Then the idle goes between 800 and 500 rpm and the engine feels like it’s going to stall, but never quite does. No codes! In a way, the rough idle is now worse with this new MAFS, but surprisingly, it never stalls like it used to with the previous MAFS.

Returning from work late in the evening, when the driving pattern is reverse, I get all the way home without any rough idling (idle is not perfect but I would say not pathological in this case). In this reverse driving pattern, I first drive 6 miles on city streets and stoplights and I don’t get any rough idle. The engine reaches operating temperature within the first 2 miles. Then I drive about 12 miles on freeway and then finally 2 miles on city streets and stoplights close to my house. I don’t get any rough idling on these last two miles. Basically I don’t get any rough idling at all on my return trip home.

When I changed the MAFS, I read a pending code P0171 (mixture lean), after one round trip to work (2x20miles). But it was only a pending code, and I think it’s was likely because the new MAFS is different than the old one. I cleared the code and did not get another one in the next two days driving back and forth to work.

In any case, if it were a vacuum leak, it would not take 30’ to manifest itself. Would it? I imagine once the engine warmed up (5mins at most) it would have started causing symptoms. No?


3) So (today) I TOOK APART AND CLEANED THE IACV (Idle Air Control Valve):

Was challenging to remove without removing the throttle body, but with some contortions and McGuyver screwdrivers I managed.

?? Now, QUESTION: is the IACV supposed to stay A LITTLE OPEN when the solenoid is not connected ??

In other words, is the spring inside the IACV supposed to keep the valve completely closed?
Because that was the only thing that struck me perhaps as a little suspicious. The IACV was not completely closed when the solenoid was disconnected.
Otherwise, the IACV did have a small film of carbon deposits but did not seem unusual. I cleaned it with carburetor cleaner anyway.

I also cleaned the fast idle valve, since I was there, and I also took out the four fuel injectors and cleaned them, they did not seem dirty. I put things back together, but still, rough idle after about 20-30 minutes.


4) I DISCONNECTED BATTERY:

And left it disconnected for 30’, just to give the ECU a chance to forget the … traumatic past. Engine was difficult to start afterwards, took 20” cranking before it started, very erratic and slow, then within another 30” it stabilized.

But still, erratic idle after about 30’.

Got another pending code P0171 (lean), but again, I think this might be because the new MAFS likely has different characteristics than the OEM part?


5) I VACUUM PUMPED the EGR with the engine idling:

Engine stalled. So I guess that means the EGR is working?

============================================

Any ideas? Especially whether the IACV is supposed to close all the way when the solenoid is inactive?

Here is a video of the IAVC not closing completely
https://youtu.be/E9Z6HbqpHvQ


And here is a video shaowing me applying on and off voltage to the IACV solenoid (I connect/disconnect the electrical connector)
https://youtu.be/7XAklJn3vQM
 
  #21  
Old 08-02-15, 01:29 PM
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Well, I’m still at a loss

VACCUM TEST:

So here is a better vacuum test. I connected the vacuum to the brake booster, but before the one way valve.
In the video you can see the rough idle:
@ 0:05 Near stall
@0:38 Near stall
@0:53 & 1:30 I revved up to 4000RPM
@1:55 Briefly opened throttle ½ way
@2:42 Near stall
This is the first time I do a vacuum test. Does the little vibration in the needle qualify as unstable vacuum?
The tinging/sputtering vibration noise you hear in the video is not the exhaust but noise from inside the vacuum gauge, perhaps the needle fluctuating?

My Vacuum test: https://youtu.be/g7GcgtUDa9o


This next video shows idling only. As I noted down the times when a near stall occurs, I see they occur almost every 30 seconds regularly. Perhaps that has some significance?

My vacuum at idle only: https://youtu.be/oBqMvjeotjI


COMPRESSION TEST:

Seeing whatever needle vibration I saw above, and seeing the paper sucked into exhaust in the “paper by exhaust” (like this guy shows on youtube: https://www.youtube.com/watch?v=PI5bBV0ZFek), and reading that it may indicate sticky valves, I decided to do a compression test.

Test was done with all spark plugs removed, throttle full open, about 7 turns of the engine (cranking to 15 turns seems to yield 3 PSI more):
Cyl 1: 162 PSI
Cyl 2: 162 PSI
Cyl 3: 158 PSI
Cyl 4: 158 PSI

I tried adding about 1tsp of oil to Cyl1 and got 170 PSI.

Nissan specs are: Standard: 178 PSI. Min: 149 PSI, Max acceptable difference between cylinders: 14 PSI.

So looks ok to me. No sticky valves? No bunt valves, no major ring and seal issues?

LOOK FOR BLOWN GASKET:

Oil looks fine, not milky
I opened the radiator and started engine cold. No coolant came out.

FUEL PRESSURE TEST:

I imagined that fuel supply issues would occur at high power, not idle. But since I have now pretty much checked everything, I went ahead and did a fuel pressure test.
I Td a fuel pressure gauge after the filter and got:
36 PSI with vacuum hose attached to fuel pressure regulator (Spec: 34) OK
45 PSI with vacuum hose NOT attached to fuel pressure regulator (Spec: 43) OK

So, all systems are checking out ok

I now do get a pending P0171 (lean) code once in a while after letting it idle for a while. I also got a P0300 but I’m not sure about the conditions since I was doing all these tests with vacuum, compression and fuel pressures.

In any case, when I took out the spark plugs to do the compression test, here is how they looked (engine had been rough idling for about 10 minutes before I took them out).

I cannot see any unevenness, implying something might be wrong with one or more cylinders.


So what is going on?

As a reminder I have also:
-Changed the MAF (ok with cheap non OEM part, since my original was noisy)—disconnecting MAF does not fix the rough idle anyway.
-Cleaned the Idle Control Valve and checked operation (spring by itself closes valve only ¾ of the way, but I assume that is normal?)
-measured the TPS resistance for linearity and the TPS switch
-Checked the fast idle settings (thermos-mechanical opening of throttle, throttle completely closed once engine warm)
-Checked the manual portion of the idle air (screw on throttle body) per shop manual procedure (If I repeat the procedure per shop manual I end up in the same ½ turn of the screw open-same as it was)
-Checked ignition timing per shop manual procedure (look for 20 deg BTDC with TPS disconnected) -- in case timing chain had skipped.
-Hand pumped the EGR valve at idle to verify that it did indeed cause engine to stall—in case EGR stuck open at idle.
-Changed front O2 sensor—in case it was about to fail and giving erroneous lean
-Put Techron in gas tank—to clean injectors
-Opened injectors to look for dirt—very little found
-Checked for vacuum leaks (not very thoroughly but vacuum measurements look good, don’t they?)

So what’s left:

The only thing I have not checked is ignition. But obviously I do have spark, so any static or simple continuity tests on ignition and coils are unlikely to reveal anything. Besides what sort of ignition issue is it that shows up only at idle? I yanked on cables, banged on distributors, disassembled distributor cap, nothing, no difference. Any ideas on the ignition?

A mystery remains, that “Paper by the exhaust test” which at my exhaust does indeed show the paper being occasionally sucked towards the exhaust pipe when engine gets into its funky idle spurt (by is this cause or effect of the fact that engine is in near stall?)

Driving me nuts !!

As an added irritation, I have to pass a smog test by the end of the month…
 
  #22  
Old 08-14-15, 11:14 PM
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Well I’m still battling it.

The good news is that I did pass the smog test a couple of weeks ago. So I have two years now to fix this problem

The bad news is that in spite of having capitulated and taken the truck to two more garages in the past week, still no success. Nobody seems to be able to find anything.

I guess the dealer is next in line to prove their worth. Hopefully I will not have to just pay for overpriced attitude.

To their credit, the two garages did not want to charge me anything since they were not successful, though I insisted on paying them $40 for the one hour or so they spent making an honest effort.

If I heard correctly, one of the mechanics told me that my Long Term Fuel Trim is at about -10% while my Short Term Fuel trim is about +24% (almost maxed out, I guess?). That seems puzzling to me. At a certain RPM after a while the LTFT should start adjusting so that STFT goes back down closer to 0. Not?

I'm thinking I should buy one of those ODB2 bluetooth or wireless tools and then download one of the many available programs (I heard Torque was good?) to verify these things myself. Anyone has any experience with those?


The garages also double checked many of the items I had originally investigated, including smoking the whole system in search of vacuum leaks but did not find any. In one mechanic’s opinion, the lean condition could cause the vacuum needle to vibrate a bit, there is not necessarily something wrong with the cylinders, valves or gasket, he said, things that were more or less excluded by the other tests anyway.
 
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