How To Diagnose/Solve High Idle Issues

[OldNuc]

Originally Posted by SC2

I have a 2001 SC2 and my high idle only returns every summer. In the winter time no high idle what so ever. Throttle body cleaned, idle air control valve replaced. Should the “summer high idle” tell me something. Yes when I turn off the engine, and start back up high idle gone. So now I am leaning towards the TPS or the coolant temperature sensor.

The turn off engine and restart for a normal idle is usually the TPS. It can also be the MAP sensor. If you have never changed the ECTS change it first as its the 10.00 part.

[SC2]

Thanks for the tip, looks like after 3 years I am on the right track. Glad to found this site.

[chad53916]

It's weird what can affect idle. I notice, even when in neutral the engine will idle high until I come to a complete stop. And when I had the wheels off the ground when changing my intake manifold gasket, I could turn the front wheel by hand and the idle speed would change slightly. Not sure if it's a friction thing in the trans or if it's a software thing.

[SC2]

I’ve had time to change the ECTS over the holidays, the old one was cracked, not split open but cracks were visible. New one went in without a problem, reset the PCM by pulling out fuse B for about a minute. The new ECTS is registering higher temperatures, before at the quarter mark the engine was warmed up, now it climbs all the way to the 3/8 mark for warm-up. I can now see how a faulty ECTS can underreport operating temperature causing high idle and excessive fuel consumption. My fuel mileage shot back up to where it should be so I am very happy with this minor fix.

Second observation is that the cooling fan should kick on sooner, as the old ECTS was under reporting operational temperatures, I can see how the engine had to be hotter than normal to turn on the fan.

I was careful not to over tighten the new ECTS, but it was hard to determine whether the pressure came from the thread sealant or the ECTS being completely in. I did feel resistance all the way through and stopped when I started to feel more resistance. Nothing is leaking as I’ve checked, and I will keep an eye on the water level for the next few days. Say you over tighten the ECTS, would you only damage it, since it is made out of brass, or would the head threads be damaged as well.

I’ll try to report back if my “summer only” high idle returns.

[mytimeflies]

hi thanks for the great tip changed ects sensor with the help of the youtube video, car is running great i have an 94 sc2 with over 300k

[OnDaGround]

***SOHC Intake Manifold Gasket Repair Guide*** This guide was provided by RC1488.

http://www.saturnfans.com/forums/sho...d.php?t=115925

[OnDaGround]

*bump for people who don't use search*

[Ecomike]

Has anyone that had these high idle problems, also had intermittent rough shifting problems with the transmission, 1-2 and 2-3 forward, and switching from forward to reverse?

Has anyone found an alternative source, reasonable cost new connector for the coolant temperature sensor?

[saturn_babe]

Silly question, but what is considered high Idle? When I'm just sitting there with the car running the rpm is at 1. Is that ok?

[OldNuc]

PM Low Saturn for a replacement connector. He is a member here.

Transmission repair
http://www.saturnfans.com/forums/sho...nput+shaft+nut

http://www.saturnfans.com/forums/sho...d.php?t=112858

Read these threads and see how your symptoms fit into these descriptions. If you have a bad ECTS the trans will not be real happy and that may be most of your problem.

You may also have an intake manifold vacuum leak, it is a common problem on your year.

Welcome to the Forums!

[OldNuc]

Originally Posted by saturn_babe

Silly question, but what is considered high Idle? When I'm just sitting there with the car running the rpm is at 1. Is that ok?

Warm engine in neutral should be about 800. If you are at 1000 that will be a bit high.

[saturn_babe]

Originally Posted by OldNuc

Warm engine in neutral should be about 800. If you are at 1000 that will be a bit high.

ohh ok... i'll have to pay more attention to it because that's when I 1st start it up and it's cold. But if it is still at 1 when warm, could it be something bad? The car runs good I think. It has 125k on it.

(you can tell I don't know much... but I'm a learning! Thanks!)

[Signmaster]

Originally Posted by saturn_babe

ohh ok... i'll have to pay more attention to it because that's when I 1st start it up and it's cold. But if it is still at 1 when warm, could it be something bad? The car runs good I think. It has 125k on it.

(you can tell I don't know much... but I'm a learning! Thanks!)

That is higher than normal for a fully warmed up vehicle. At full operating temperature (which should be right around 3/8 on the temp gauge) your idle should drop to 750-800 RPM while in neutral. This may be slightly higher if it's cold out and you are running the heat, especially if you have the heater fan cranked up.

If you aren't cranking the heat and the car is fully warmed up there is a chance either the ECTS is bad or the thermostat is bad. One causes the car to think it's not up to temp and tries to get it up to temp (the ECTS). The thermostat often sticks open when it fails, causing the car to take longer to get up to temp. That causes a proper working ECTS to try and correct the problem.

Either condition can also cause a drop in MPG. On the up side, both are cheap and easy fixes.

[Ecomike]

Thanks!

My daughter bought an 01 SL1 from a friend of mine, our first. I am a jeep guy myself, with four 85-89's, but her new jobs is boocoup gobs of miles, and and the SL1 is 31 mpg around here. I hope the random high idle is TPS and ECTS and that it is causing the tranny problem now, other wise this new vehicle is going to be an early pain.

Originally Posted by OldNuc

PM Low Saturn for a replacement connector. He is a member here.

Transmission repair
.....

Read these threads and see how your symptoms fit into these descriptions. If you have a bad ECTS the trans will not be real happy and that may be most of your problem.

You may also have an intake manifold vacuum leak, it is a common problem on your year.

Welcome to the Forums!

[OldNuc]

TPS is not usually the cause of a high idle condition that is consistent. This is real easy to check. When the high idle condition is occurring when the car is in park or neutral just turn it of and restart it without touching the gas. If that cures the high idle then it is a TPS issue and if not then it is something else. A consistent high idle is the 2001 SL-1 intake gasket leak problem and you fix it by replacing the intake gasket. The intake gasket leak is also found on some 99, 2000, and 2002 cars. A DIY job that takes the inexperienced about 4 hours. There is a detailed how to posted here. http://www.saturnfans.com/forums/sho...ghlight=gasket

[diplomat1]

Thanks for the write up. Im just confused as to how i would check for vacuum leaks for a DOHC engine because in your post it says SOHC and not DOHC. Can i use the same method on a DOHC 94 sl2 engine? Thanks

[quantumech]

Originally Posted by diplomat1

Thanks for the write up. Im just confused as to how i would check for vacuum leaks for a DOHC engine because in your post it says SOHC and not DOHC. Can i use the same method on a DOHC 94 sl2 engine? Thanks

The same method SHOULD work.

[diplomat1]

Coo imma try it tomorrow. Thanks guys

[saturn_babe]

Originally Posted by Signmaster

That is higher than normal for a fully warmed up vehicle. At full operating temperature (which should be right around 3/8 on the temp gauge) your idle should drop to 750-800 RPM while in neutral. This may be slightly higher if it's cold out and you are running the heat, especially if you have the heater fan cranked up.

If you aren't cranking the heat and the car is fully warmed up there is a chance either the ECTS is bad or the thermostat is bad. One causes the car to think it's not up to temp and tries to get it up to temp (the ECTS). The thermostat often sticks open when it fails, causing the car to take longer to get up to temp. That causes a proper working ECTS to try and correct the problem.

Either condition can also cause a drop in MPG. On the up side, both are cheap and easy fixes.

I was out this morning. It was 30 degrees. My idle with the car warm and heat off is still at 1000. And it stays the same with the heat full blast. My temp gauge was at 1/4 mark and doesn't go over that ever. So I guess it needs something. I'm thinking that throttle thing needs cleaning cause I was reading last night about the gas pedal getting hard to press sometimes and mine does that. Could that also cause slightly higher idle? Sorry for all the questions, but i appreciate the answers!!!

[alordofchaos]

Originally Posted by saturn_babe

I My temp gauge was at 1/4 mark and doesn't go over that ever. So I guess it needs something.

If your ECTS ($10) is good, then you need a thermostat ($25).

Either the ECTS is sending a bad signal that your engine is colder than it really is, or (due to failed thermostat) the engine really is colder than it should be. This tells the engine to add a little gas and idle a little faster to help your engine warm up to normal temps. Normal gauge reading for 96-02 should be around 3/8

I'm thinking that throttle thing needs cleaning cause I was reading last night about the gas pedal getting hard to press sometimes and mine does that. Could that also cause slightly higher idle? )

Sticky gas pedal is likely a separate issue (throttle body, most likely, as you have already found)