Idle not returning/ Possible Throttle Cable problem?

[way2slowtalon]

This is about my 98 Eclipse Rs Automatic. I have a funny situation whee my car idles normally 800 rpms, but other times about 1200rpm. Also I can travel 45 miles an hour, get off the gas, and will coast without rpms or speed going up or down. It feel like cruse control is on. I was told me Throttle cable could be stuck, and there was a recall with the dash pad? According to Mitsu my car has all it's recalls done and no problems with this model.

What can cause this? TPS? Throttle cable? Oh btw no CEL lights, or vac leaks. Is this my car not returning to idle position or is it more serious?

Thanks

 

[absolute_DSM]

If you let off the gas and your speed stays the same, youve got problems. That is very unsafe.

You should go into your engine bay with the car off and twist the plate of the TB to see if you can feel it sticking. If you have cruise, there are a couple more cables that could be sticking. (Follow them around the engine bay)
Just start disconnecting them one by one and testing them out to see which one the culprit is.

 

[way2slowtalon]

If you let off the gas and your speed stays the same, youve got problems. That is very unsafe.

You should go into your engine bay with the car off and twist the plate of the TB to see if you can feel it sticking. If you have cruise, there are a couple more cables that could be sticking. (Follow them around the engine bay)
Just start disconnecting them one by one and testing them out to see which one the culprit is.

Yup, the speed is staying the same sometimes. I will go through the cables this morning, So it can only be a Cable right? Not blown Auto tranny, or anything funny like that?

 

[DSMcrazy3]

Tranny wouldn't cause that.

 

[absolute_DSM]

Exactly, tranny wouldnt do that.

Yes it should only be a cable.

Just a tip and me rambling -
With mechanics, before you begin to diagnose any problem, you have to remember to start with the most simple things and work your way towards the problem. Dont jump to conclusions, go back to the basics and act like you dont know anything.

Think electronics, just cause your car wont start and your gettin a clicking from the starter solenoid but it wont crank.. doesnt mean you need a new battery or a new starter. Start simple and check the battery terminals, then work your way down the chain from there.

Youd be surprised how many times the simpliest things cause the biggest problems.

 

[way2slowtalon]

Checked all TB cables, (i do have cruise control). Didn't notice anything wierd about them, returned to normal, and car went back to normal while driving. SOOOO I pull in the driveway and it started happening again.

This is very inconsistent.

 

[absolute_DSM]

Did you disconnect them from the TB to check them out? Thats the only sure way to tell if they are sticking.

 

[Doug99RS]

The accelerator cable area in question is right here. Check this area and make sure it's not causing a problem. There's still a chance that the cable could be frayed going in to or coming out of the cable sleeve either in the cabin or in the engine compartment.
Doug

 

[Shadow98]

I just recently installed my 55mm throttle body and have had problems with the RPMs not coming down. When I get home to make adjustments to it the RPMs start going up and down from ~900 to ~3k (before I do anything). Does yours do this? I'm going to change my IAC since it has a lifetime warranty and the cables seem to be fine. If it works for me it might work for you. I'll let you know what happens tomorrow; since I just got off drill and got to take at least a 2 hr nap before showing up for my 12 hr shift tonight.

 

[Doug99RS]

If you've got an aftermarket throttle body then you'll also want to consider the possibility that the throttle plate is not shutting all the way. With the TB remove from the car open and close the plate VERY slowly several times and make sure that there is only a small sliver of light shining through between the plate and the TB housing. If you've got much more than that then your throttle plate screws may need to be loosened up and the plate may need to be moved side to side.

If your throttle body is NOT aftermarket DO NOT MESS WITH THIS PLATE AS IT IS NOT THE CAUSE OF YOUR PROBLEM.
Doug

 

[Shadow98]

Well, the IAC valve did the trick on my car.