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Fuelly Ford


crosswind's Avatar
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04-27-03, 05:37 PM   #1  
crosswind
Fuelly Ford

1993 Ford F150, 5.0 Ltr, 4Wd, 190,000 miles. Here's one with lots of miles..........There is a sensor of some sort mounted to the side of the throttle body. When I was having trouble with the idle, I pulled the plug on this unit to see how it would change the operation of the engine. When I unplugged the sensor, the idle speed immediatley dropped to a normal level (from 23000 down to 7000). Plug it back in and the idle will not drop below 20000. Only problem, this sensor must have something to do with the choke operation when the engine is cold. With the sensor unplugged, the choke does not function, you must keep the engine running with the gas pedal until it warms up. Also, it seems that the engine can flood out really easy when trying to start if you dont get it to fire the first time. Question is, what is this sensor? What is it's function? Surely it needs to be replaced, but will that fix the problem? Also, I have not yet had the throttle body cleaned out yet since last post. That will need to be done as well.

 
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04-27-03, 06:19 PM   #2  
Sounds like the Idle Air Control (IAC) valve. It adds/subtracts air from the intake tract to control idle speed and the choke function. They are prone to carbon fouling. You can take it off and soak it in Gumout to knock some carbon loose if you think it's not functioning properly, but the ECM should throw a code if it senses the IAC isn't having the right effect on the A/F ratio.

Jim

 
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04-28-03, 05:50 AM   #3  
Joe_F
If it's a long cylindrical looking thing with a kinda triangular shaped base and has 9F715 in the # stamped on it, it's an idle air control valve.

I agree with Jim. Probably wasted or you have a dirty throttle body.

 
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04-29-03, 07:29 PM   #4  
crosswind
I took the IAC valve off and found it to be very gummed up, then i took off the throttle body and could hardly believe that this truck would run. there was more build up than you could imagine. so I took it off to clean it. After taking off the throttle body, I could see yet more build up in the intake manifold, so i am proceeding to take it off. I need a good torx screwdriver to get the last bolt off though. Surely cleaning off all this build up help. There were ports in the throttle body that were completely clogged. The cylinders in this engine must be shot. engine runs well though, i have only had problems starting it occasionally. Feels like it floods out way too easily .

 
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04-30-03, 06:29 AM   #5  
Joe_F
That will do it .

 
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04-30-03, 04:46 PM   #6  
While you are in there see if there is a metal filter under your pcv valve grommet.If its clogged clean it while you are there,it will cause a ton of problems if you don't.

 
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04-30-03, 05:52 PM   #7  
Joe_F
Very true, agree with Davo.

 
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05-03-03, 03:55 AM   #8  
crosswind
Okay.....Which part is the PCV valve. I know what it is, i kind of know what it looks like, but so many of these things look the same. I guess I can find it in the manual. One more question. If all of this carbon build up and gummed up parts are in the intake portion of the engine, where is it coming from. The engine sucks in fresh air through a filter. I know there is a connection from the valve cover to the air filter case. I know that some oil gets into the filter area from that connection. What would cause that? Thanks for your help.

 
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05-03-03, 11:22 AM   #9  
Joe_F
The PCV system helps burn oil vapors. If it's not working right (bad valve, holes in the lines, etc), it may cause oil to form in the air filter housing, so get that working in short order. Yes, use the manual to guide you as to where it is, or use the underhood emission decal.

If the PCV system is fixed and you still get oil in the air filter, the engine has blowby (usually bad rings) and is on borrowed time. A rebuild would correct that.

 
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05-04-03, 06:01 PM   #10  
crosswind
I have cleaned all the intake parts or replaced them: IAC valve, throttle body, intake manifold, PCV valve, Misc hoses, gaskets. Engine started great, idled much higher due to the better air flow I guess. increased idle from 7000 to 14000 with IAC disconnected. with IAC connected, increased from 24000 to 37000 RPM way too high. Do you think I still need a new IAC or is there another part that is not functioning properly here. Also, after running a few minutes, I turned it off and then tried to restart. Once again, it flooded out and wouldn't start. What should I do next?

 
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05-05-03, 09:08 AM   #11  
Joe_F
Likely wiped at this stage of the game, I'd replace it. Did you use the proper cleaner on the throttle body? Most times on Fords you have to use their approved cleaner so you do not damage the throttle body.

 
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05-06-03, 09:13 PM   #12  
If you haven't done so yet ,i'd suggest removing the negative battery cable from the battery for about 5 minutes,which will clear the computer.restart the truck if you can and let it run for a while.If it still is idling to fast ,check for vacuum leaks.These are bad about vacuum leaks around the upper intake area where it bolts down to the lower intake.

 
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05-20-03, 05:53 PM   #13  
crosswind
now that I have cleaned all the parts, the engine runs alot better. Starts well, idles at about 1100 RPM, until it heats up. Once the engine reaches operating temp, the idle rises up to about 24000 RPM. A quick hit to the gas drops the RPM;s down to 1100 again, but it quickly rises back up. I have not found a vacuum problem yet, but it sounds like the IAC is shot.

 
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05-21-03, 04:02 AM   #14  
Joe_F
Did you try testing it?

 
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05-21-03, 04:08 PM   #15  
crosswind
how do you test it? Do you mean get a diagnostic test done on the engine?

 
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05-22-03, 06:34 AM   #16  
Joe_F
Test the IAC valve...

What does your service manual and autolibrary have to say?

 
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