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Old 09-11-2016, 01:10 PM   #1
GTS350
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1999 SC2
Default 1999 SC2 automatic is this normal?

When I come to a stop and as I'm slowing down the RPMs will go down to about 1100-1200rpms (which seems high) than when I'm at a COMPLETE stop it drops to about 750rpm (which seems normal). Is this normal behavior for this car?

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Old 09-11-2016, 07:10 PM   #2
Saturn Night
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1995 SC2
Default Re: 1999 SC2 automatic is this normal?

Quote:
Originally Posted by GTS350 View Post
When I come to a stop and as I'm slowing down the RPMs will go down to about 1100-1200rpms (which seems high) than when I'm at a COMPLETE stop it drops to about 750rpm (which seems normal). Is this normal behavior for this car?
Can you clarify between slowing down and stopping?

Are you trying to say that "as you are slowing down/braking"(decelerating from "x"mph to 0mph), that the rpms remain between 1100-1200, and then at a stop, it goes from the 1100-1200 range slowly down to 750-800?

The stopped rpm range seems normal.

Have you checked your fluid level, with the car level and having operated for at least 15 minutes?

Do you have any "Service Engine Soon" codes coming up?

Are there any other drivability issues, such as misfire, stalling, surging?

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Old 09-12-2016, 12:07 AM   #3
GTS350
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1999 SC2
Default Re: 1999 SC2 automatic is this normal?

Quote:
Originally Posted by Saturn Night View Post
Are you trying to say that "as you are slowing down/braking"(decelerating from "x"mph to 0mph), that the rpms remain between 1100-1200, and then at a stop, it goes from the 1100-1200 range slowly down to 750-800?

The stopped rpm range seems normal
I agree the stopped range seems normal to me as well. That's why I wondered if this was a characteristic (albeit extremely annoying characteristic) of the car.

Your description of the problem is just what I meant with the exception being when I complete the stop (0mph) the idle drops quickly to 750-800rpm other wise exactly the way you discribed it.
When I am completing the stop (less then 3-4 mph) I am having to brake harder to overcome the RPM's of the engine.
Car:
Low milage, no error codes, all fluids recently changed, TB, EGR, PVC valve all removed and cleaned (no real carbon build up) new ECTS. It did this before this work and after.
prior to the above work the car passed CA smog (high but passable NO at low speed) 0ppm at 25mph.

Other than the above the car appears to be running fine. My only other complaint is that the car appears to be slow. I don't know if these 2 issues (I have never owned or driven a Saturn before) are actually issues or simply characteristics of these cars.

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Old 09-12-2016, 07:01 AM   #4
Cheyne
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2000 SL2
Default Re: 1999 SC2 automatic is this normal?

Having to brake hard to overcome those rpm at 3-4 mph likely indicates a failing TPS. If put in park, the rpm will likely increase to 1500+. If so, turn off engine and restart. If this results in normal 750 rpm, replace the TPS.

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Old 09-12-2016, 09:41 AM   #5
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2002 SL2
Default Re: 1999 SC2 automatic is this normal?

Cheyne may be right. The TPS affects shifting performance. A great way to see what the ECM (engine computer) is reading while the throttle position changes is to hook up a scan tool with LIVE DATA. One of the lines on the scan tool screen will read "TPS %". What that means is how much does the engine computer think the throttle is open at any given time. If, when the throttle is closed (foot off the gas pedal), the TPS % reading is above zero, then Cheyne is right. The TPS is faulty and should be replaced.

Another possibility is that the throttle body is gummed up with carbon and the throttle plate may be getting stuck open a tad as you release your foot from the gas pedal. This could be easily fixed by simply removing the throttle body, cleaning it, and re-installing. This would also remedy any "stickiness" you feel when pressing on the gas pedal. It is good maintenance anyhow.

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Old 09-12-2016, 01:07 PM   #6
GTS350
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1999 SC2
Default Re: 1999 SC2 automatic is this normal?

Cheyne:
When put in park the RPM's do not go to 1500 they stay at 750-800rpms
Bachands:
As I mentioned the throttle body (as well as EGR and PVC) has already been removed and cleaned even though there was no real carbon build up on them.

I will look into the TPS next. Are the TPS on these cars adjustable?

Last edited by GTS350; 09-12-2016 at 01:19 PM..

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Old 09-12-2016, 02:19 PM   #7
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Default Re: 1999 SC2 automatic is this normal?

No adjustment on the TPS. These are just simple resistive potentiometers, no amount of adjusting can ensure proper operation once a pot gets worn and flaky... The "zero" point is automatically checked/calibrated at every key-on, I think, but that may not help much if the TPS is bad.

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Old 09-12-2016, 02:26 PM   #8
GTS350
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1999 SC2
Default Re: 1999 SC2 automatic is this normal?

I found this in another post.
"The idle will ALWAYS be higher when the car is moving. It should settle down to 800-ish when you stop, but as long as the PCM detects the car is moving, it'll nudge the idle up to 1200-1400-ish."

Is this in fact true?

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Old 09-12-2016, 02:35 PM   #9
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1997 SC1
Default Re: 1999 SC2 automatic is this normal?

My *warmed up* car idles at ~650+/-20 rpm (foot on brake), ~750+/30 in neutral, park and with the AC on (foot on brake). Upon cold startup RPMs start at ~1200 and then settle down to the previous mentioned #s.

I'm pretty sure that's normal for an SOHC. You have a DOHC

http://www.saturnfans.com/forums/sho...d.php?t=133266

Last edited by lil_buddy; 09-12-2016 at 02:40 PM..

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Old 09-12-2016, 02:53 PM   #10
Cheyne
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2000 SL2
Default Re: 1999 SC2 automatic is this normal?

Quote:
Originally Posted by GTS350 View Post
I found this in another post.
"The idle will ALWAYS be higher when the car is moving. It should settle down to 800-ish when you stop, but as long as the PCM detects the car is moving, it'll nudge the idle up to 1200-1400-ish."

Is this in fact true?
Yes, but you shouldn't have to brake much to bring it to a stop. A failing TPS will cause the car to sometimes feel somewhat like it is mildly accelerating when bringing it to a stop. It can also cause the car to feel like it is accelerating on its own somewhat when taking the foot off of the brake.

The TPS fault is usually intermittent, thus it will not always show when put in park. Most people, however, realize they have the problem not while decelerating but rather when they actually put it in park. It can also be verified as mentioned by bachands with the live data on the scanner.

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Old 09-12-2016, 03:10 PM   #11
GTS350
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1999 SC2
Default Re: 1999 SC2 automatic is this normal?

Quote:
Originally Posted by lil_buddy View Post
My *warmed up* car idles at ~650+/-20 rpm (foot on brake), ~750+/30 in neutral, park and with the AC on (foot on brake). Upon cold startup RPMs start at ~1200 and then settle down to the previous mentioned #s.
I'm pretty sure that's normal for an SOHC. You have a DOHC

http://www.saturnfans.com/forums/sho...d.php?t=133266
When you are coming to a stop and you let the car slow down on its own it will idle down to 650 +/-20 rpm, correct?
Mine will only go down to 1100-1200rpm unless I step on the brake and bring the car to ZERO mph then it will drop to 750-800 range.
With the car warmed up it does this 100% of the time.
Everything else appears to be normal.

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Old 09-12-2016, 03:18 PM   #12
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1997 SC1
Default Re: 1999 SC2 automatic is this normal?

Quote:
Originally Posted by GTS350 View Post
When you are coming to a stop and you let the car slow down on its own it will idle down to 650 +/-20 rpm, correct?
Mine will only go down to 1100-1200rpm unless I step on the brake and bring the car to ZERO mph then it will drop to 750-800 range.
With the car warmed up it does this 100% of the time.
Everything else appears to be normal.
Idle means 100% stopped - 0 mph. What you are describing is coasting and coasting rpm's are dependent on many external factors. For example, rpms can increase if you are headed downhill even though you are not pressing the gas to accelerate. Also, when you are coasting and the car downshifts, you will see a little rpm surge.

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Old 09-12-2016, 05:13 PM   #13
GTS350
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1999 SC2
Default Re: 1999 SC2 automatic is this normal?

Quote:
Originally Posted by lil_buddy View Post
Idle means 100% stopped - 0 mph. What you are describing is coasting and coasting rpm's are dependent on many external factors. For example, rpms can increase if you are headed downhill even though you are not pressing the gas to accelerate. Also, when you are coasting and the car downshifts, you will see a little rpm surge.
I understand how a car with an automatic transmission works. What your not understanding is when I attempt to stop it is as if I am holding the gas pedal to 1100rpm and at the same time pushing the brake in an attempt to stop until I am no longer moving, then and only then will my RPM's drop to the correct range. This is not normal.

According to live data using Torque
The Throttle position (manifold) at idle in Park Neutral, or Drive is .4 which sounds correct (Can someone confirm?).
When driving when I release the throttle it drops to and stays at .4 the whole time including down to the initial 1100 and when the RPM's drop to 750 the throttle position remains at .4 this number is consistent when I let off the throttle from any RPM

Here are a couple things I noticed if this helps diagnose.
This happens in forward or reverse
If I slow down and just before stopping let off the brake the car will accelerate and continue to drive at 1100rpm as if I was holding the throttle.
However from a stop if I let off the brake and let the car move on its own it will do so at the 750rpm as it should.

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Old 09-12-2016, 05:39 PM   #14
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Default Re: 1999 SC2 automatic is this normal?

If you are for example, going uphill at 10mph on gravel, rpms will hold steady at over 1000 rpm? Is that what you are saying?

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Old 09-12-2016, 08:15 PM   #15
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1995 SC2
Default Re: 1999 SC2 automatic is this normal?

Change the TPS. And check your CKP, regarding the "slowness", which may also be affected by a failing TPS. It never hurts to inspect the CKP. They are prpne to failure.

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Old 09-12-2016, 08:48 PM   #16
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Default Re: 1999 SC2 automatic is this normal?

That's normal operation. The idle air controller raises the idle while decelerating. Its effect on braking effort should be minimal to negligible. If you really notice it causing undue braking effort, I would check the brakes.

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Old 09-12-2016, 11:47 PM   #17
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1999 SC2
Default Re: 1999 SC2 automatic is this normal?

Quote:
Originally Posted by madpogue View Post
That's normal operation. The idle air controller raises the idle while decelerating. Its effect on braking effort should be minimal to negligible. If you really notice it causing undue braking effort, I would check the brakes.
If this is "normal" than your saying lil_buddy car in not normal for behaving the way every other car behaves. His is obviously normal and there is something wrong with my car.

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Old 09-13-2016, 01:36 AM   #18
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2002 SL2
Default Re: 1999 SC2 automatic is this normal?

Quote:
Originally Posted by GTS350 View Post
Bachands:
As I mentioned the throttle body (as well as EGR and PVC) has already been removed and cleaned even though there was no real carbon build up on them.

I will look into the TPS next. Are the TPS on these cars adjustable?
My mistake...I missed that info from your earlier post.

I think I'm understanding what you're saying. Instead of the RPMs slowly coming down to idle as you come to a complete stop, they get "hung up" around 1200 until the very moment you stop. Then the RPMs shoot down to around 800. Is that correct?

If so, that is abnormal. Why would it do that though? Hmmmm

I'd still go for the TPS or the TPS wiring being faulty. You stated that the value for the TPS % while the throttle is completely closed is 0.4. It should really be 0.0%. That's what I've always seen for my Saturns when reading LIVE DATA. But 0.4% is a rather small difference. It's hard to believe that would cause such a problem. However, replacing the TPS with another one is still the next logical step in diagnosing the problem, IMO.

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Old 09-13-2016, 11:34 AM   #19
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1999 SC2
Default Re: 1999 SC2 automatic is this normal?

Quote:
Originally Posted by bachands View Post
My mistake...I missed that info from your earlier post.

I think I'm understanding what you're saying. Instead of the RPMs slowly coming down to idle as you come to a complete stop, they get "hung up" around 1200 until the very moment you stop. Then the RPMs shoot down to around 800. Is that correct?

You stated that the value for the TPS % while the throttle is completely closed is 0.4. It should really be 0.0%
The way you discribed the behavior is correct.

I thought a reading of 0 on the TPS meant 0 (or off) Can someone confirm their live data number for TPS on idle?

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Old 09-13-2016, 12:05 PM   #20
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1999 SC2
Default Re: 1999 SC2 automatic is this normal?

How can I test the IACV.

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