High idle issue

[Slugger865]

Hopefully someone can tell me what's wrong without seeing it, I ill describe it the best I can. When I am in neutral and I rev it up it seems to take longer than it should to idle back down to normal. Also sometimes when I come to a stop it will idle at about 1500 for a minute then drop back down to 1000. I just replaced the throttle control sensor 2 weeks ago. Any suggestions will help. Thanks!

 

[Archer Fabrications]

Idle speed controller, boost leaks, fiav valve, front o2 dieing?

 

[goldeninja20]

First thing that comes to my mind is that the tps was not adjusted properly when you replaced it.

 

[Slugger865]

I didn't adjust it at all... How do you adjust it? I don't see anywhere to adjust anything.. Just bolt on and plug in is all I did.

I should also mention that I just replaced the intake manifold gasket and had to take off the throttle cable bracket. Could it be possible that I put it back on too tight? How do you tell if it is?

 

[91-GS]

Since this is a non-turbo, it's one of the adjustment mechanisms (most likely one that make the car idle faster when cold). It, and an electronic idle adjusting module (operated by ECU) are on the bottom of the throttle body and can be taken off by undoing five bolts, couple of coolant hoses, and an electrical connector. These modules are not all that important, car will run fine without them. Had same issue as you so took the module off and blocked off the holes that were there.
Something like this is what you will need to do that. Be sure to loop the coolant hose so coolant can still flow like it did before. Leave the electric plug hanging there, just make sure it won't get into any moving parts. After the plate is on and the throttle body is mounted back on the car you will have to back out the BISS screw a bit to get her to idle right. Do it after the engine has warmed up. The BISS is located on top-front of throttle body, pointing up-forward. Is usually under a black plug that you will have to remove.

How do you adjust (the TPS)?

2G TPS adjustment.

 

[goldeninja20]

Since this is a non-turbo, it's one of the adjustment mechanisms (most likely one that make the car idle faster when cold). It, and an electronic idle adjusting module (operated by ECU) are on the bottom of the throttle body and can be taken off by undoing five bolts, couple of coolant hoses, and an electrical connector. These modules are not all that important, car will run fine without them. Had same issue as you so took the module off and blocked off the holes that were there.
Something like this is what you will need to do that. Be sure to loop the coolant hose so coolant can still flow like it did before. Leave the electric plug hanging there, just make sure it won't get into any moving parts. After the plate is on and the throttle body is mounted back on the car you will have to back out the BISS screw a bit to get her to idle right. Do it after the engine has warmed up. The BISS is located on top-front of throttle body, pointing up-forward. Is usually under a black plug that you will have to remove.

Since this is a non turbo (420a). there is no adjustment for tps and no biss screw. Nor is there any coolant hoses running to the throttle body. Your only issue could be iac or too tight of a throttle cable. You should be able to grab the throttle cable and there should be some slack in the line.

 

[91-GS]

Since this is a non turbo (420a). there is no adjustment for tps and no biss screw.

My bad, thought he has a 4G63.

 

[Archer Fabrications]

Or a vac leak

 

[jayson427]

I think a vacuum leak would rev up more then 1500rpm. so I would take your throttle cable off again and make sure its adjusted right. I have slack in my cable after it comes off of the bracket on the intake manifold don't make it too tight. but it could just be the iac I would take that off and clean the spring inside and see if that helps too. the iac is right under the tps.

 

[Archer Fabrications]

Not necessarily, could have a small crack somewhere, a leak doesn't have to be a gaping hole.

 

[Slugger865]

I checked for a vac leak and did not find one. The guy at autozone told me to spray starter fluid on the lines and if it revs high then there is a leak. I also sprayed around the intake manifold and nothing happened. Where is the iac located? I will try to clean that. What do I clean it with?

Bump..

 

[goldeninja20]

It is on the upper half of the throttle body (firewall side). I would clean with brake cleaner, although dont go crazy as it is electronic and you dont want to ruin it. If i was you, I would remove the whole throttle body and clean the entire thing because they do build up with carbon.

 

[Slugger865]

I cleaned the throttle body and the iac. There was a ton of carbon build up on the butterfly. Tested the iac by hooking it up and turning the ignition on and off. The iac would go in but not come back out so I ordered a new one...