fast idle when car is rolling

[billjohnson426]

I have a 94 sl2 with the dohc. it has 138,000. great runner. The only time the idel drops to 800 is when the car is not moving. I can be doing 55 mph push in the clutch and pull it out of gear and it will still idel at 1800. once the car hits about 2mph or stopped it will finally drop to 800 rpm hot or cold. any ideas on this one???

[sierrap615]

the computer sets different idles for when moving and stopped. saturn rule of thumb - if any thing is wrong(even more so with a wierd idle) change the ECTS. but also check the service records for when was the last time the fuel filter was changed or the injectors were cleaned.

[binnemg]

I'm having the same problem with my '97 SOHC. I replaced the IAC and the problem was fixed, everything was great. I let my son drive the car and suddenly the problem re-appeared. I changed the PCV valve and checked the ECTS and it did not improve. Can't believe a IAC valve could mess up in 3 months but don't know where else to look. Any suggestions out there?

[Lucas1]

unless its idleing high when at a stop i wouldnt worry about it. the computer gets info from the speed sensors, (and several other inputs) and adjusts the RPM accordingly. if it sees that you are going 55 MPH it doesnt make sense to drop all the way down to 800 rpm. keep in mind that on a manual trans, the PCM has no idea what gear you are in. if it were to drop the rpm that low and you stomped on the gas, acceleration would be very slow.

so from what your saying it seems like a normal condition, unless there is more to it..............

[binnemg]

The situation is such that when I am shifting gears the RPM actually goes up when I put in the clutch. It idles at 1600 to 1800 when the vehicle is in motion and slowly drops down to 800 when I come to a full stop. This is exactly what it did before, so I changed the IAC. Now I am wondering if the PCM is somehow burning out the IAC. My Chilton book says that the reference voltage at the IAC should be between 1.5 and 10 volts, and I am getting a full 12 volts.

[binnemg]

OK, last night I was stuck in traffic and the coolant temperature went up a little higher than normal and the idle problem disappeared. So . . . it looks like the engine coolant temperature sensor is the culprit afterall. I assumed that the ECTS was a basic on/off, hot/cold type sender unit, but it must send a more linear signal and the idle adjusts in several stages to the signal.

[jgtatl]

Originally Posted by binnemg

OK, last night I was stuck in traffic and the coolant temperature went up a little higher than normal and the idle problem disappeared. So . . . it looks like the engine coolant temperature sensor is the culprit afterall. I assumed that the ECTS was a basic on/off, hot/cold type sender unit, but it must send a more linear signal and the idle adjusts in several stages to the signal.

I have noticed that my temperature gauge has gone up and down when driving long distances but as far as the idle problem, I have been having the same exact problem for a while now. It doesnt seem to drop when shifting or in neutral. Only when I stop completely. It drives me crazy. I read that someone recommended to change the ECTS. Im not sure what that is exactly. I just was told that it was my clutch which I found hard to believe. How much is the ETCS (around) and where is it located on the car? and sadly enough I have to ask what is it. Im supposing its a part of the computer but Im really not sure. Any help or suggestions would be so gladly appreciated..Thanks

[binnemg]

The ECTS is the Engine Coolant Temperature sensor. I don't know which engine you have but on the SL1 it is located on the side of the engine block, on the drivers side of the car. It is a small sensor that screws into the block and has two wires coming out of the end. You'll need to unclip the plastic connecter taking the two wires off, and use a deep socket to take the sensor out. Have the new one ready, and wrap the threads with teflon tape for a good seal. As soon as you take the sensor out the coolant will start to dribble out, so have the new one ready to screw in right away. The sensor isn't very expensive at all.

[jgtatl]

Did you say that by replacing the ECTS it helped correct the while rolling high idle problem? I cant figure out why it does that. I just had the fuel injectors cleaned and it still does it. It used to only do it when it was cold but now it always does it.

[sierrap615]

I've also noticed sometimes bad driving habits will cause a high rolling idle. but most of the time its the ECT. it does output a linear signal, cost less then $20. the old nylon ECTs failed massively, they were replaced by a redesigned all-brass ECTs. the ECT is the main input for the PCM to decide the air/fuel mixture. also, a bad ECT will tell the computer the engine is colder then it actully is, so the PCM will add more fuel to warm up the engine. another bonus to fixing a bad ECT is that you will get better gas mileage ( $$$-it will pay for itself quickly). go visit saturnfans.com for more information