Vacuum and surging idle

[Psydwaze]

My idle is surging and I've cleaned everything; IAC, MAF, and verified TPS voltage at .98v. I haven't checked my timing or fuel pressure but last time it was done I set it to 37psi and 10 degrees. Now... if I unplug a vacuum line anywhere in the system the idle smooths out. What the heII does that mean???

 

[HISSIN50]

since you are creating a vac leak, i would think (even though i know you went over it) that your IAC is not up to par.

my two cents. good luck.

 

[Psydwaze]

I checked both leads at the IAC with a test light. One is 'hot', the second only provides ground when the car is running. Is there a way to tell if the IAC motor is working correctly?

Also, I ran codes.

CODE: 11 (KOEO) - System Pass
Engine: 5.0L
Year: 86-93
Description:
System Passes this test


CODE: 44 (KOER) - Right Thermactor Inoperative
Engine: 5.0L
Year: 86-93
Description:
Thermactor air system inoperative (right side)

CODE: 94 (KOER) - Left Thermactor Inoperative
Engine: 5.0L
Year: 86-93
Description:
Thermactor air system inoperative (left side)

Is 'air' meaning 'AIR' the acronym. Air Injection Reaction (SMOG stuff)

I just pulled these at The Corral. The list I had previously didn't specify left or right so I assumed this had something to do with the smog system. Left and right leads me to believe these are my O2 sensors. Can someone confirm this?

 

[HISSIN50]

i believe you are supposed to check the resistance between the terminals (i cant recall which - i do seem to recall that the ISC has a diode in it and if you try to test it incorrectly, you can do harm). ill let the puter guys (JR, et al) chime in.

good luck.

 

[jerry beach]

I would remove and clean the TB (throttle body) real good. Dont worry about those thermactor codes. My books says they are secondary air injection codes, left and right. These components fit the same decription. Both deliver air to the converters in the exhaust.

 

[blk92stangg]

Check for coking around the throttle plate, as well as proper throttle plate adjustment. Seems like the IAC is the only thing maintaining your idle, possibly due to not enough air going by the throttle plate at closed throttle. When you pull a vacuum and allow unmetered air in, the engine has enough air for idle, and the IAC can relax. Try resetting the idle on the car with throttle plate and body cleaned. It's free, and worth a try.

 

[TheUser]

the right and left codes refer to the thermactor...your smog system (if you have one) should lead to the back of each head which is where the thermactor is...one in each head....smog junk...if you have a smog delete, then that's why.

 

[Psydwaze]

...proper throttle plate adjustment. Seems like the IAC is the only thing maintaining your idle, possibly due to not enough air going by the throttle plate at closed throttle.

I did notice my throttle plate sticking closed a bit when using the linkage at the TB to bring up the revs. I'm going to installed a Idle Adjustment Spacer from Ford then the throttle plate can stay closed at idle. I will clean it tonight before adding the spacer next week. Thanks for the suggestions.


TheUser: So you're saying the 44 & 94 codes shouldn't affect my idle? I did check the smog pump and its pumping air. I have voltage to the solenoids and vacuum. But, I'm not exactly sure when they are and aren't supposed to open the valves.