Idle troubles

[93rev2sev]

So I've been trying to track down an idle problem in my 90. When the car starts, it's idle is rock solid 1100RPM for a moment and then it drops to 900 or so...just like it should.

the fun starts after it's been running for a few minutes. Most of the time the idle will start to bounce at a stop. It does not bounce EVER if the car is rolling (more than 2 miles an hour or so).

As soon as the car slows to a stop...the idle begins to degrade. It bounces further and further until it just stalls.

Here's what it's NOT...
Poor grounds
DIS
TPS
IAC
Intake manifold Vacuum leak
Throttle body
Dirty MAF

What are the chances that it could be:
Defective MAF
Defective coil pack
Defective B9B computer

Other suggestions?

 

[yzstud]

i know ur a very knowledgable man, but i must ask, have u checked for codes? :scared:

 

[bubba]

I would say it has something to do with the maf, Something has to be up with it... I did want to say it was the IAC though

 

[Ishodu]

Sounds to me like the IAB is sticky so the car is having issues with controlling it smoothly. If its stuck the ecc is asking it to open more and more and its not moving then bang it moves and gives a big gasp of air, then it tries to close a little and its stuck and then bam its closed and so on.

 

[Tecchie]

Take it out (this is what I did and it worked for me, if you break your shit, it's not my fault) the IAC/IAB valve that is.... First, touch the contacts with a multimeter, if you get between 7 - 12ohms you're money.. (or 9 and 12, can't remember) if it's within those values then just clean it and oil it..

This is what I did.
Removed
Cleaned with B-12 (love that stuff) and let soak and rocked back and fourth for a min
drained and repeated until the fluid ran clear...

Then put some clean new motor oil in it, moved it back and fourth with some needle nose (the plunger that is) and then drained it... then shot some WD40 in there and repeated...

Drained, wiped clean, reinstalled.. no more problems..

It may be totally un-related but mine is the original one from Ford that I can tell and I have a 1995 ATX 208K on clock.

And for me personally, if I can fix a part and it still works, I'm golden as I am a cheap bastard and can't afford alot anyways, and sure beats over $100 for a new one...

EDIT:

Before I forget, once I saw all the nasty crap come out of mine I proceeded to clean the **** out of my intake also... nasty...very.....nasty....

 

[93rev2sev]

I've already replaced the Intake Air Controller...the whole intake, actually. It DOES seem related to the IAB...but more to the signal the IAB is getting and not the IAB itself. If I use a nickle to prop open the throttle at the throttle stop and disconnect the IAC, it idles rock solid for hours. As soon as I plug in the IAC it starts to bounce.

AGAIN: I know the IAC is good.

The intake I used came from a perfectly running, lower milage engine. So the DIS, IAC, TPS, Throttle are all ruled out...It definately acts a little like a vacuum leak, so I took the intake off and was going to re-seat it and decided just to put a known good intake assembly on.

Unplugging the MAF does not help...though I'm not convinced it's not the culprit. I've been over the grounds and I'm starting to think it's either a bad MAF or a bad computer.

 

[jmpSHO]

I would say a bad MAF and sometimes just cleaning it won't help, you might need a new one. It also could be your IAC. I know you say it's new but I just had this problem on my Explorer. I bought a new one and it still didn't idle right and I returned it for another one and idles perfect.

 

[Ishodu]

So the easy thing to do now is reset idle see what happens.

 

[Green Sho]

I have a similar problem and it goes away when you disconnect the vacuum line on the throttle body that goes to the purge canister solenoid. As soon as I disconnect that line it starts suckin air big time and the idle levels out nice. I would check this solenoid.

I also tried replacing it with a few junk yard ones but they all didn't work. Still lookin for a new one!