Idle problem when started

[MilTownSHO]

Today when I would start the 92 SHO, I would say 3/5 times it would be running rough and the idle would bounce a little around 800-1200 rpms. It would even go as low as 500 on an occasion or two, if I give it some gas, it would stop and then be fine until I turned off the car and restarted it.

Any ideas?

 

[Joe'sSHO]

How's the TPS. Is it stalling at all? Sounds like a TPS to me if it isn't stalling.

 

[MilTownSHO]

Joe'sSHO:
Is it stalling at all?

Doesn't stall

 

[NotSoSlowSHO]

ditto on the TPS.

You might want to clean your MAF sensor and AIB valve as well.

Also, any CODES?

 

[sdpatt]

It would be a good first step to try resetting the idle speed. There may be a dead spot in the TPS around idle. You can test the TPS or have it tested by AutoZone for a continuous and linearly increasing/decreasing output. If there are any dropouts in the respinse, a new TPS should solve the problem. There is a chance that the cause is internal to the electrical portion of the IAB valve and cleaning it would have no effect. They get a dead spot in their feedback just like the TPS. Only replacement will correct the problem.

 

[Zxarkov]

I use to have the simalar problem with my '90. I found the problem to be the IAB, which can easily be removed and cleaned with carb cleaner. The Instructions for this can be found at shotimes. Good luck

 

[projectSHO89]

Scott,

There's no feedback mechanism INSIDE the IAB. It is a simple linear actuator driven by a variable duty cycle drive signal working against a spring.

Feedback is via the measurement of PIP.

Steve

 

[MilTownSHO]

sdpatt:
It would be a good first step to try resetting the idle speed.

I just reset the idle speed a little over a month ago after my A/C clutch got adjusted so it quit cutting out. Seemed fine today, didn't do it at all. I will check on the TPS and clean the IAB (I did it to my white 91.)

The car should be in storage next week, so I may not get around to it, I was just trying to get an idea, thank you!