Eratic Idle Problems - Toyota Nation Forum : Toyota Car and Truck Forums

jjames · 12-14-2005, 07:36 PM

My daughters 95 Celica GT has developed and eratic idle problem. It started off idling very low around 400 rpms I bumped the timing to 15 and that helped some. Then it started dying all the time. I found I had low compression in the number 1 cylinder so I did a head job but found nothing wrong so it must be in the lower end. But now the car has started reving on its on, it will jump from 1000 rpm's up to 3000. Under normal driving the car runs perfect no misses nothing. The only problem is during idle and now it does a combination of all these things it lopes, it dies, it idles low. But sometimes it will run just fine it has run perfectly for the last two weeks. To date I have replaced both O2 sendors I have replace the Air conditioner compressor because Toyota's have a low idle sensor inside them. I have replace the Air temperature sensor in the air box. I did the valve job replaced all gaskets and o rings for the injectors i have had the injectors cleaned professionally twice. I replace the Idle Air control sensor under the throttle body. I just don't know what else to do several mechanics have looked at it and blame it on the low cylinder about 80 PSi but I don't believe it. It doesn't smoke all plugs burn nicely and all the cylinder heads where blackened evenly when i did the head. it does use some oil but not much. What else can I check? i have set the timing at several locations and checked as much electrical as I could. The only thing I haven't done is bought a new cumputer. I was also told that the air flow meter may need adjusting. It has also been referred to as a mass air flow sensor. It should be mounted on the air box correct? It's not there. Nor is there a loose wiring harness laying around. The Haynes manual says there should be one but there's not. There is also NO idlke screw under a rubber plug in the throttle body. Someone please help before I have to sale her dream car.

Nad1370 · 12-15-2005, 01:12 AM

Quote:

Originally Posted by jjames

low cylinder about 80 PSi but I don't believe it. .

^^ Believe it . This is your problem.

A compression this low will idle low, run rough at idle , and will cause to die out coming to a stop. But it will run fine while cruising.

Your rpms shoot up because the ecu is trying to compensate for the low and rough idle so it lenghtens the injector duration and opens the IAC motor to get an ideal mixture at idle.

Sorry to hear you had to perform all those unneccecary repairs where you should have been fixing the obvious fault.

BTW. I think this has a MAP sensor not an MAF. Might be bolted up in the firewall close to the T-body. 3 or 4 wire with a vaccum hose.

Good luck on your deciscion.

Pineapple · 12-15-2005, 11:39 AM

95 Don't have idle screw, idle is control by the idle control valve, ICV. Did you replace the whole valve or just the green electical part? 90% of eratic idle is caused by dirty ICV. Remove intake pipe from throttle body and clean the bottom 2 holes in it with throttle body cleaner if you haven't done that yet.
BTW minimum compression is 142 psi, you'll need to get it fix.

jjames · 12-15-2005, 02:38 PM

Yes I did replave the whole IAC. And I did find the Map Sensor but to tell you the trith I cannot turn loose of another 384.88 for a map sensor if I am not sure it will solve my problems. As faras the compression goes it doesn't make sence to me that it could cause all these problems because the car sometimes runs fine for weeks so its not like the car all of a sudden gauined compression. But then again I am not a mechanis more of a parts changer than anything.