Help! Idle revs high at stoplights up to 1500rpm

[AABoca]

2000 SL1, 5 speed stick -
Mileage is approx 198,xxx .

Issue I am having is the Idle revs high at stoplights up to 1500rpm , and after exiting from highway driving sometimes up to 2500rpm . I did have the throttle cleaned by my indy 2-3 weeks ago and that didn't stop the hi idle. First I read that this could be the ICM , and was ready to order one and then I read that the ICM may have nothing to do with it and it could be a few other things or on some sites read it can never be fixed and they are built in like this. So before going back to my indy I can turn a wrench ( with instructions) I am looking here for anyone who can take me through diagnosing and fixing this problem.

Thanks!

[2NDSOUT]

Verify with your mechanic that they actually REMOVED the Throttle Body from the car and CLEANED it. Simply spraying Carb cleaner in the Throttle Body while it is still mounted in the car will not sove this issue.

Additionally, while the Throttle Body is out, check and replace the TPS (Throttle Position Sensor).

If you go onto Youtube and look up Richpin06a, he is a member here that has a large amount of How-To Videos. There is one on cleaning out the Throttle Body. This is something you can do yourself rather then paying an independent mechanic hundreds of dollars per hour to clean something.

[fdryer]

As a new member, search and read all about the engine coolant temperature sensor (ECTS). Just remove yours and examine it; if its the round nosed plastic one then replace it immediately with a flat nosed brass one from any auto store stocking it.

It would be wise of you to do this first before doing anything else............

[AABoca]

How is the ECTS effecting my idle ? My engine temp is always steady & my AC knock on wood is excellent.
Thanks!

Austin

Originally Posted by fdryer

As a new member, search and read all about the engine coolant temperature sensor (ECTS). Just remove yours and examine it; if its the round nosed plastic one then replace it immediately with a flat nosed brass one from any auto store stocking it.

It would be wise of you to do this first before doing anything else............

[2NDSOUT]

Originally Posted by AABoca

How is the ECTS effecting my idle ? My engine temp is always steady & my AC knock on wood is excellent.
Thanks!

Austin

The ECTS is also tied into other various others things related to the idle as well.

[AABoca]

Thanks. Will check it.

AA
...

[fdryer]

Originally Posted by AABoca

How is the ECTS effecting my idle ?

Search for the numerous posts on what this coolant sensor does when it fails to operate..................you won't have to go far.

[BV22]

An also search Throttle Position Sensor. When these are failing, you get an idle in the 1500 to 2000 rpm range, but if you shut the car off and restart it without touching the gas, the ilde returns to normal until the next stop sign or traffic light.

[johnny95sl2]

Intake manifold gasket failure. pretty easy fix

[RobertGary1]

Originally Posted by johnny95sl2

Intake manifold gasket failure. pretty easy fix

Not impossible but down on the list of most common causes.

Where does your temp run on the gauge after driving long enough to warm up?


-Robert

[AABoca]

There are no #s on the base model, but gauge is always steady even down here in Miami area in August after 100 miles highway and AC on high. Always stays on the first line to the left.

Originally Posted by RobertGary1

Not impossible but down on the list of most common causes.

Where does your temp run on the gauge after driving long enough to warm up?


-Robert

[AABoca]

It is the round plastic one. Hoping for the time Friday or Saturday.. * I have run only about 2 gallons of reg unl fuel since I added to fuel additive (Startron, no affiliation) and either coincidence or today I noticed my idle was not as high as usual today. I've used this stuff religously on my Old Diesel Benzs, and it is better than any other additive I've heard of. Can this idle be maybe a fuel related issue too?

..

Originally Posted by fdryer

As a new member, search and read all about the engine coolant temperature sensor (ECTS). Just remove yours and examine it; if its the round nosed plastic one then replace it immediately with a flat nosed brass one from any auto store stocking it.

It would be wise of you to do this first before doing anything else............

[fdryer]

The round nosed plastic coolant sensor is the very first item to eliminate and is the main problem, period. If you aren't willing to search any threads about it, so be it. Your loss (of information/education). Just replace it immediately.

You're also wasting money on fuel additives. You're driving a gasoline operated engine, not a diesel that has its own issues different from gasoline engines. Stop throwing away money. The replacement coolant sensor will most likely cure most of your issues you're not willing to search about it here on Saturnfans.

And yes, this sensor is causing your idle issues, among many other issues........... The sooner your replace it the sooner you might see a direct change for the better. And if there are any remaining problems then address those after this is taken care of.

[2NDSOUT]

If your temp gauge is still staying at the 1/4 mark, there is some stuff going on with the Thermostat being stuck in one position.

Let's go step by step here. Change out the ECTS first. If this doesn't change things for the better (it should); I would keep an eye on the temp gauge. If the temp gauge STILL doesn't move, then it's time to move to draining the coolant and changing out the Thermostat.

In all honesty, it may not be a bad idea to do this. Considering that you will lose a decent amount of coolant from the block when you change out the ECTS, you may as well change out the Thermostat while you have some of the other coolant components out anyway. If you have no record of the T-Stat being changed, it may well be original just like your ECTS. These parts don't last forever.

[RobertGary1]

Originally Posted by 2NDSOUT

In all honesty, it may not be a bad idea to do this. Considering that you will lose a decent amount of coolant from the block when you change out the ECTS, you may as well change out the Thermostat while you have some of the other coolant components out anyway. If you have no record of the T-Stat being changed, it may well be original just like your ECTS. These parts don't last forever.

I believe I measured it the last time I did this job. It was around 2 teaspoons of fluid lost. That area of the head doesn't hold much coolant.

However, if it were me, I would also do both the thermostat and the ECTS knowing that both are common issues on these cars. Be sure to *ONLY* buy the STAT brand thermostat. Autozone's first listing is a below OEM temp thermostat for this car and you don't want it. This car works best when running at the temp that the PhD's who engineered this stuff saw best.

-Robert

[AABoca]

Are you always such a charming guy? I am on this forum 1 day and already getting insulted. I appreciate the tips and FWIW kiddo I searched and read through a bunch of somewhat related posts. * Try eating some prunes or plums for the constipation.

Originally Posted by fdryer

The round nosed plastic coolant sensor is the very first item to eliminate and is the main problem, period. If you aren't willing to search any threads about it, so be it. Your loss (of information/education). Just replace it immediately.

You're also wasting money on fuel additives. You're driving a gasoline operated engine, not a diesel that has its own issues different from gasoline engines. Stop throwing away money. The replacement coolant sensor will most likely cure most of your issues you're not willing to search about it here on Saturnfans.

And yes, this sensor is causing your idle issues, among many other issues........... The sooner your replace it the sooner you might see a direct change for the better. And if there are any remaining problems then address those after this is taken care of.

[AABoca]

Thank you but I think you are taking what I wrote too literally. By not moving I am trying to convey that the temp is steady. Of course the needle moves during driving but it doesn't get hotter than just under the first 1/4 marking.

Originally Posted by 2NDSOUT

If your temp gauge is still staying at the 1/4 mark, there is some stuff going on with the Thermostat being stuck in one position.

Let's go step by step here. Change out the ECTS first. If this doesn't change things for the better (it should); I would keep an eye on the temp gauge. If the temp gauge STILL doesn't move, then it's time to move to draining the coolant and changing out the Thermostat.

In all honesty, it may not be a bad idea to do this. Considering that you will lose a decent amount of coolant from the block when you change out the ECTS, you may as well change out the Thermostat while you have some of the other coolant components out anyway. If you have no record of the T-Stat being changed, it may well be original just like your ECTS. These parts don't last forever.

[fdryer]

The same question always comes up from doubting Thomas' and I try to be as brief as possible. Its meant to provide blunt honesty. I you don't like it then just ignore my posts......................my bowel movements are fine, thank you.

[RobertGary1]

Originally Posted by AABoca

Thank you but I think you are taking what I wrote too literally. By not moving I am trying to convey that the temp is steady. Of course the needle moves during driving but it doesn't get hotter than just under the first 1/4 marking.

Driving around at the 1/4 mark is not good and points to your problem. It's so super common that you could just find the solution with Google. The factor used defective ECTSs and thermostats get old and tired.

[AABoca]

Originally Posted by RobertGary1

Driving around at the 1/4 mark is not good and points to your problem. It's so super common that you could just find the solution with Google. The factor used defective ECTSs and thermostats get old and tired.

Went to Advance and they wanted $47 for Google. Will stick with the new ECTS.

Thanks, AA