High Idle Issue

[MrQ]

Worst it can do is not work, so I would give it a shot.

 

[sroth004]

Thanks for the quick response: That is true, didn't expect any negative impact but thought I'd ask.

A friend suggested replacing the Throttle Body, which was cleaned in a cleaner tank by the Ford dealer last Fall. Any thoughts on that?

Really appreciate the input, thanks.

 

[410Fortune]

replacing the throttle body will do nothing, as the throttle body is a very simple device
As long as the gasket is good and the butterfly moves freely the TB is good, you already cleaned it

You adjusted the idle stop screw earlier in this thread
THEN you found the hole in your intake tube allowing in the un metered air
Did you ever return the idle stop screw to the stock position?
Did you ever inspect the upper and lower intake gaskets for a possible air leak?
a 1994 engine is getting up there in age, the stock gaskets likely need to be replaced, a good time to inspect and re ring the fuel injectors as well
(If you do head gaskets then the intake gaskets will all get done at the same time, so mute point)

After that then I would suspect the PCM, they are known for strange idle issues when they start to go south

 

[sroth004]

Thanks guys, I appreciate the input and questions. I did not think the Throttle Body would cause this either, one of the reason I focused on the PCM as the next step. I did replace both head gaskets and all related gaskets (intake, etc...) as part of that process. Actually did the work at a friend’s repair shop with his oversight so I have some degree of confidence I didn’t mess-up that work. I did recheck the throttle body stop screw as part of the head gasket, intake tube, etc...repair as it was all done at the same time.

I installed the replacement PCM a few minutes ago, off for the test drive.

Steve

 

[sroth004]

Hello all, wanted to circle back to everyone on the idle issue. I installed the replacement PCM (ECU) last weekend which appears to have finally resolved the issue. Each of the suggestions helped, for example I did find and correct a few vacuum leaks, but Turdle and MrQ's recommendation about the ECU from a while back seems to have put this to bed.

Thanks everyone for the ongoing help, the next and hopefully last project is to replace the rear wiper motor, hopefully an hour and then done until the next repair.

 

[smegun]

Hello all, I am chasing an idle issue on my recently purchased ‘94 which now has approx. 69,000 miles and am hoping the group can point me in the right direction. I did own a near exact vehicle in the 90s so I know the behavior is not normal. The symptoms and what I’ve already done to try and resolve the issue are as follows:

Symptoms
- When purchased in July I noticed there was no high idle at cold start up and that on occasion the truck was slow to return to normal idle when coasting down to 0 mph.
- Being Summer, the lack of high idle did not affect drivability too badly however now in Winter the truck will not run/idle on its own until warm and is still very slow to return to normal idle when letting off the gas. When warm, it hangs at about 1,200 rpm and eventually drops to about 600-700 rpm 15-20 seconds after releasing the accelerator pedal.
- I have noticed that resetting the ECU by disconnecting the battery seems to resolve the issue temporarily however over a few days the symptoms reappear incrementally, almost as if a sensor is faulty and the ECU is adjusting for the faulty sensor which then causes the starting/idle issue to occur.

Having researched the heck out of the issue on this Forum and elsewhere I and my local Ford dealer have done the following:

- I inspected, cleaned and ultimately replaced the Idle Air Control Valve with an OEM (Hitachi) unit. I did reset the ECU and as described above this resolved the issue for only a few days.
- I adjusted the idle stop screw and ended-up with it where it was originally; no change
- Dealer replaced the IACV again with a Motorcraft part as it believed the IACV I installed was defective; no change
- Removed and soaked the Throttle Body to clean; no change
- Neither I or the dealer tech can hear a vacuum leak, though it was not smoke tested and I cannot guarantee there is no leak
- There is no check engine light and both I and the dealer separately confirmed there are no Ford-specific or OBD codes

Any suggestions on next steps? MAF? Coolant Temp Sensor?

Thanks in advance.

Steve R

check line to fuel regulator if not pulling a vac right it will surge the idle much higher