1988 Ford LTD Country Squire - Cold Idle

My wagon has decided it doesn't want to idle when it's cold. If I tap the gas pedal, keep the RPM's up a hair, it'll warm up and be fine. If I try to leave and drive too soon, it's not happy either - sputter, maybe a stall.

I figure a couple things maybe:
Mass Airflow Sensory gunked up
Throttle Body dirty
Maybe fuel filter
Vacuum leak

I tried to pull some codes using the old jumper method, but the only thing I get is a steady ENGINE light just like I do every time I go to start the vehicle. The ENGINE light is otherwise not on.
(I followed this dudes instructions - wrong car, but same basic idea, right?
)

Any other clues or things I should look for or am I screwing up the code reader thing?

 

Try cleaning the idle air bypass valve (sometimes referred to as IAS). It is on or near the throttle body on Fords. The passageways can get pretty gunked up. Depending on the engine, the resistance through the solenoid can be anywhere between 6 and 14 ohms.

 

That's what was wrong with my friend Steven's '87 Grand Marq--the IAC was bad. You can clean it, but if the stepper motor is frozen, the cleaning will not help it.

 

And a steady CEL during the self-test can indicate problems with the test connector wiring or the computer. I use a 12 volt test light to give a separate indication in case of computer problems.

 

THanks y'all. going to try and mess with this today.

 

Cleaning didn't do anything - which I thought it wouldn't once I got it apart and the pintle/spring/little rod thing in the middle moved freely. Got it back together, had the same issue. Then I realized I forgot to plug the IAC back in, and got my hopes up to only have them crushed like many of my other hopes and dreams when it kept doing the same thing.

The voltage to the IAC was fine, came in about a 9.8. Damn thing just doesn't want to idle much at all now so I'll drop the 50 bucks on a new one, see what happens.

 

New IAC and no dice. Still doing the same deal.... any other suggestions? I took a video, please forgive the quality of the video, yay for smart phones.

 

Possibly a bad coolant temp sensor telling computer wrong. Like an old car with choke not working. You say its ok when warmed up.

 

You also have to remember that Fords require a number of starts-warmups-driving at operating temp-cooldown (usually between 20 and 50) before it relearns the entire idle regime. My friend's Grand Marq is running much better now that it's gone through that over the past couple months.

 

Worked on many Fords and never had a computer take that much time to adjust to a part change.

 

If someone messed with the throttle stop screw (as they had with Steven's), that can cause a problem with the TPS voltage, but it's rare anyone attempts it. Other than that, a problem with the ECT would have to be a circuit short. Unplug the ECT and start the engine. If it's that, you will get full enrichment (computer will think it's -40* F), but with little to no idle relearn, the IAC may not give the desired result. Also, unplugging the ECT should test the computer's ability to sense a circuit fault ànd store a hard code.

 

Don't forget to check the condition of any vacuum hoses.

 

I'll take it for some drives. I didn't know it took that many runs to get it going how it needs. I did have the battery disconnected for the entire process of replacement.

The stop screw is untouched from what I can see, just as dirty and no strip/screw driver marks.

The vacuum hoses I can see all seem to be fine, maintenance records show many of them have been replaced over the years. I'm afraid I'll have to break down and take it to my mechanic.

I'm going to take it for a drive and see what happens. Pay more attention to driving at speed, WOT, etc...

 

Took it out for about a 30 minute drive.

Pulls OK, sometimes at 40-45 MPH might get a sputter. At idle, in gear, it's very ... lurchy? ( )

Could it be a simple fuel flow problem, like a fuel filter or something? Vehicle has 195,000 miles on it.

Electronic Ignition Module, distributor cap, rotor button, replaced at 160,000
New plugs, wires at 162,000
Going back to 8/20/1997 87,272 miles, the idle speed was adjusted and seems to be the last time the fuel filter was replaced

 

Your best investment would be a scanner like e-bay item # 231623010278 to check codes. Cheaper than a mechanic on an hourly rate. Never hurts to change fuel filter. Fuel pressure needs checked with proper gauge . The temp sender for ecm will cause all you describe. It is the sender with 2 wires not the one for temp gauge or light on instrument panel.