kidkodiak

I know a nominal amount about these two things, so these should be easy questions for y'all pros

The IAC... is it true that it only affects the idle speed before the engine reaches temperature? I read that on a post here from a while back... I had assumed it always regulated the idle air flow. I'm going to replace it... after cleaning it, my TPS and my TB really good with TB cleaner... my idle is still at like 200rpm =\

The TPS... what does it do besides set throttle position? (I know, dumb question). It's part of the ECM, right? So it regulates something... throttle position. But besides the obvious, what else is it reponsible for? Could it have a bearing on my idling problems?

And last question... I had a guy tell me that the TPS isn't a plug n' play part, so to speak, but needed to be adjusted. Is that true? If so, what do you do when you buy a part and want to fix it yourself

Thanks so much, all.

Abovetimberline

The iac is used at all times not just until the engine is warm,the only item in the loop that is not used is the 02 sensor,it has to be 900 degrees before it can make voltage,until it does your control system is in what is called open loop,once it reaches temp it goes into closed loop,that is why 02 sensors have little heaters in them,to get them into closed loop quicker,the tps is used for all inputs in regards to throttle position for transmission,timing,injectors,etc,the tps needs to be adjusted if it is adjustable to insure proper idle,transmission shift points etc.

mike37

IAC alway controls the idle regardless of temp

tps tells the ecm the position of the throttle so it can give proper fuel for the amount of air interring the cylinder

on a 2001 it should be plug and play what motor do you have

kidkodiak

Thanks guys, both responses helped a lot. Mike this is on my 1990, not the 2001... it's reaching that point where I'm troubleshooting a bunch of different non-related things all the time now.

This is my current "must fix" problem... my low idle


How do I know if it's adjustable? Is the adjusting something that requires special tools to do?

Abovetimberline

1990 is adjustable and it is important where it is,you will have a high or low idle if not adjusted right and trany can be effected also assuming you have an aw4.

kidkodiak

So I can bolt on a new IAC, but the TPS I should probably have a pro do? At least, someone who knows how to "set" them?

mike37

so its a HO not a renix
HO plug and play but verifying voltage is a good idea
renix must be adjusted

if the bolt holes that hold it on allow it to rotate its adjustable

Abovetimberline

91 was the first year for the ho.

kidkodiak

No, the 1990 is a Renix. And yes, the bolt holes allow it to move before you tighten it down... aye carumba, I wonder if this is part of the problem.

When I pulled it, cleaned it and replaced it, I just put it back on... could I have messed it up by repositioning it improperly? I didn't think the adjustment was in the literal position of the sensor! (I know, Im a noob) =\

mike37

no your timing will be fine

read this it will give you the steps for testing all your sensors
http://www.lunghd.com/Tech_Articles/...iagnostics.htm

kidkodiak

Sweet, I'll do that.

Thanks so much for the help guys!