IAC issue?

["Turbo-T"]

Took the TR to a car cruise in yesterday. I get 20 miles from my house and am coming up to a stop light. As I stop the car sounds as if I am trying to push on the gas pedal while holding the brake.

I put the car in neutral and the rpms go up to like 2000 or so for about 5 seconds, then drop back down to 750. It didn't do this anymore for the rest of the trip.

It has done this before but not as high of rpm.

Just wondering if this is an IAC issue? Can it be corrected?

 

[ericmccann]

That would be my first guess (IAC). I'm not sure how you would test it since it seems like an intermittent, non-repeatable issue. A VAC leak may also cause surging, but it would be more consistent. Have you tried to pull any codes from the ECM? The paperclip trick (jumper pin A to pin B, then turn on the ignition, engine off, count the SVS light blinks) on the ALDL connector works well if you do not have a Scanmaster. It probably will show nothing, but it's good to check anyway since it takes all of 2 minutes and requires no tools.

Could be a leaky intake gasket as well, but unlikely. How does it run otherwise?

My .02 cents.

Best,

Eric McCann

 

["Turbo-T"]

Yeah I have a Scanmaster, no codes and the SES light has never come on ever since I've owned the car. (close to a year now) The car usually runs pretty good otherwise. I heard another TR that did it too.

 

[Tony Shoaff]

Make sure the TB is clean and not causing the throttle plate to stick??

 

["Turbo-T"]

I'll check but last I remember the TB wasn't sticking. I just did recently clean it.

 

[asd60303]

mine does the same until it warms up but in the winter/cold mornings it's worse. I'm gonna keep checking this thread to see what you find.

 

[Just a Six??]

Make sure when you set IAC you also reset TPS as they affect each other.

 

["Turbo-T"]

It did it again today. I even put the car in neutral and the rpms were like around 1800. It didn't come down after a few minutes either. I even tried blipping the throttle a few times but to no aval. IAC on the Scanmaster I can't remember but they were in the double digits.

 

[bmackinnon]

IAC on the Scanmaster I can't remember but they were in the double digits.

That doesn't help much... Sounds like maybe the iac is gunked up and getting 'sticky'... I couldn't tell above whether you cleaned just the TB or the IAC itself. If you haven't ever cleaned the iac, you'll probably find a heck of mess in there. Just pull it off and get after it w/ carb cleaner (O2 safe). Another possibility is that the iac connection is getting a bit flakey, and occasionally losing contact for a flash, causing the iac to be 'lost' to the ecm, which takes a bit, maybe even a key cycle, to regain it's bearings... Next time it happens, log the SM iac count pattern in the ole' mellon!

 

["Turbo-T"]

I want to say the IAC was like 47 or something while I was doing like 20 mph thru town with it in neutral.

I'll write it down the IAC reading next time. I ended up putting the car back in gear and driving it a little way, then stopped and put it in park, the idle then goes back to normal.

I cleaned the TB the last time i had the elbow off which was maybe 4 months ago, and I've not even put 1000 miles on it since.

 

[Just a Six??]

How old & dirty is the IAC you have? Could be really dirty at the pintle & its sticking so clean it properly first as mentioned or its just starting to go bad on you maybe? I bet the pintle is sticking from Crud!

 

["Turbo-T"]

Not really sure. I've never had the IAC apart since taking ownership literally a year ago. Is this a quick and easy job? (Sorry I've never taken an IAC apart before) Are there any tips or tricks I should know?