Bad Idle Air Control Valve?
 

Hello, my '89 22re pickup is having a rough idling issue. It idles fine when cold (1500-2000 rpm) but as it warms up the idle gets rougher and lower. I took off the throttle body and cleaned it as well as the IACV and it looks pretty clean. Is there anyway to check the IACV before we spend $180 on a new one? Could the valve be closing too much as it gets warmer?

I think on the 1989 22re you have the wax type of IACV. I'm not sure there is much to really go wrong, sounds like you have a proper cold idle. Assuming that it works like my earlier 1988 IACV, you can pinch the air hose from the IACV when cold and your idle should drop, that will tell you that the IACV is indeed open when cold. And then when engine is warm, idle should have dropped, and then you can pinch the hose and there should be no change in the idle.

Could be a vac leak in a line that is only open when engine is warm, such as the EGR system, maybe your temp sensor needs to be cleaned\checked to make sure the ECU is getting the proper temperature reading.

Could I block off the EGR from the intake plenum and see if the warm idle changes? What could change between a hot and a cold engine to make it run rough?

Check your coolant temp sensor. The green one near or on the iacv. Betcha thats the problem.

Check your coolant temp sensor. The green one near or on the iacv. Betcha thats the problem.

The idle valve is intended to close off air through that port completely, no it can not close too much.

Get the engine warmed up and check the engine speed it wants to run smoothly at by backing out the idle adjustment screw, it's completely possible its just set wrong.

Ensure the IDL contact on the tps is closed when the throttle isn't open, without a proper signal the ECU may open the vsv for the egr modulator.

Have you checked the timing?

Yes you can plug the EGR port but it's not recommended, the engine system expects it to be there, it reduces combustion temps, you are quite likely to introduce a leak behind the throttle plate.. And on and on the reasons not to continue.

Please keep us updated if you find the solution. I have been chasing a low idle after engine warms up for a while now. Have replaced many parts (including the IACV, TPS,all EGR components & every vacuum hose) and problem persists. Even swapped out the TB with another one. Also replaced TB intake hose & throttle cable.

Thank you all for the replies. :great:

I haven't checked the timing yet but I've cleaned the throttle body really good but that didn't help. Right now I'm having the IAC valve soaking in carb cleaner to get it as clean as I can get it. I did swap out the coolant temp sensor with a Duralast one but it ended up splitting in half a month later and it didn't change the idle either (It wasn't fun getting the threaded part out!). I put back the original and I may get an OEM sensor from 22reperformance.com for $30. I cant find any vacuum leaks visually but I can try spraying some carb cleaner and see if I can find one. I heard it could be a bad EGR valve too, how could I check that?

No CEL on by the way. All ignition and fuel component have been changed because its been sitting for over 10 years. Its weird too, it ran fine when we started it 5 years ago, I don't know what could have changed. Took it out for a little spin a few weeks ago too and it drives great, just idles like crap and occasionally stalls. I will check the idle screw once its all back together and I will keep you guys updated as well.

I think we've found the issue. We had a mobile mechanic take a look at the truck for $80 and he found out the first two fuel injectors had a small leak. He sprayed some carb cleaner while it was running and the truck revved up. So I guess I need some new seals, good luck with your truck.

did he spray carb cleaner on the fuel injectors or in the throttle body, and I know this was from 2019 but did it really solve the problem?

The carb cleaner is just an easy way to find a leak. If there is a leak, it will cause the idle to change due to increased combustion. The problem was likely fixed by rebuilding the injectors.