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Old 09-13-2016, 01:31 PM   #21
lil_buddy
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1997 SC1
Default Re: 1999 SC2 automatic is this normal?

I am inclined to believe the behavior described is normal. I am skeptical that the TPS is faulty.

Engine braking is very gentle on my Saturn compared to other cars I have driven. When I back off the gas it decelerates very slowly compared to other cars; it takes several minutes to see a 20mph decrease on level ground. This actually makes it difficult to coast to a stop without having to brake - which is the only way you will witness a smooth linear rpm decrease.

If you want to see the rpm come down in a linear manner without braking, coast uphill.

Here's some other threads that address the concerns expressed in this thread...
http://www.saturnfans.com/forums/showthread.php?t=96381

Posts #123 http://www.saturnfans.com/forums/sho...&postcount=123
and #124 http://www.saturnfans.com/forums/sho...&postcount=124
in the following thread http://www.saturnfans.com/forums/sho...d.php?t=207290

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Old 09-13-2016, 01:48 PM   #22
GTS350
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1999 SC2
Default Re: 1999 SC2 automatic is this normal?

Quote:
Originally Posted by GTS350 View Post
How can I test the IACV.
Figured out how to test IACV will do it later today and post findings.

Now if I can figure out how to delete or edit my post (this forum layout is not user friendly) I won't have to post twice.

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Old 09-13-2016, 02:07 PM   #23
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1999 SC2
Default Re: 1999 SC2 automatic is this normal?

Quote:
Originally Posted by lil_buddy View Post
I am inclined to believe the behavior described is normal
How can this be normal when you said your car doesn't do this? Is your car the one that is not normal? And our cars were designed to surge when your trying to drop?

I have owned 40-50 (driven or raced several 100) cars from every decade from 1908-2016
I think everyone will agree (except lil_buddy) this not normal.

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Old 09-13-2016, 02:15 PM   #24
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Default Re: 1999 SC2 automatic is this normal?

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Originally Posted by GTS350 View Post
you said your car doesn't do this
No. You misread.

All I told you were the normal idle rpms are for my SOHC car. I also linked you to a thread where normal idle rpms for your DOHC car are cited. According to that, your car is idling at normal rpm.

I'm actually confused about the nature of your issue. You are suddenly calling it 'surging' which indicates increasing rpm in the absence of gas, but your 1st post says the rpms decrease (but not in a manner you think is appropriate) which is not surging.

Last edited by lil_buddy; 09-13-2016 at 02:27 PM..

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Old 09-13-2016, 03:15 PM   #25
GTS350
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1999 SC2
Default Re: 1999 SC2 automatic is this normal?

Quote:
Originally Posted by lil_buddy View Post
I'm actually confused about the nature of your issue. You are suddenly calling it 'surging' which indicates increasing rpm in the absence of gas, but your 1st post says the rpms decrease (but not in a manner you think is appropriate) which is not surging.
No you misread I repeatedly said the RPMs only decrease when the vehicle has come to a complete stop.
When I am trying to slow down or completely stop and the RPMs are at 1100-1200rpm the vehicle is in fact surging since like I said it's attempting to accelerate while I am attempting to decelerate.

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Old 09-13-2016, 03:33 PM   #26
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Default Re: 1999 SC2 automatic is this normal?

I asked, "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?"
You ignored.

I am skeptical that your car's rpms will never decrease and stay at 1100rpm forever if you don't apply the brakes - which is what you seem to be suggesting.

It is not surging if there is no actual increase; that's according to the actual dictionary definition of the word surge.

I encourage you to continue testing and determining the condition of your vehicle; I am not trying to discourage. Null results are crucial in the expansion of knowledge. Just hang on to those OEM parts with only 23k miles on them; don't toss 'em until you are 100% sure they are defective.

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Old 09-13-2016, 04:23 PM   #27
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1999 SC2
Default Re: 1999 SC2 automatic is this normal?

Quote:
Originally Posted by lil_buddy View Post
I asked, "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?"
You ignored.
I thought it was a joke. Yes it does it on gravel as well as on grass, cement, dirt, pavement, etc.
Quote:
Originally Posted by lil_buddy View Post
I am skeptical that your car's rpms will never decrease and stay at 1100rpm forever if you don't apply the brakes - which is what you seem to be suggesting.
I didn't say forever, eventually it would run out of gas.

Why would you be skeptical? Have I done something to make you think I would post non existent problems with made up symptoms?
This is in fact exactly what it is doing that is how I know it's not normal.

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Old 09-13-2016, 05:52 PM   #28
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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, true. Emissions controls over rides almost everything in specific situations. Manual xmission drivers see this peculiarity all the time when shifting to neutral while off throttle and coasting down to a stop. Usually, when driving at speed, rpm's are up and as soon as throttle is let off, there's a specific instance where DFCO occurs. Deceleration fuel cutoff occurs when above idle rpm, at speed and throttle is closed; the pcm detects zero throttle pedal application and cuts off injectors, quickly dropping rpm until around 1200 rpm when injectors resume operation. The equivalent of trucks using their jake brake to stop diesel injectors from operating and using engine compression to slow down. Everyone hears it and it's a very distinctive exhaust sound as it's loud. DFCO is used when fuel isn't needed to coast from speed but emissions resumes a higher idle to prevent the catcon from cooling off (the front O2 sensor needs be hot/closed loop operation) otherwise the EFI system goes from closed loop emissions control to open loop mode. By keeping a high idle, emissions is in control. As soon as a lower speed is reached (5-15 mph?) this 1200 rpm high idle drops back to normal idle. The engine should be slowing the car during this phase and not make it hard to brake at all. Your descriptions seem occur at zero(0) speed when high idle drops back to normal. Something is skewing this operation and shifting it to zero speed instead of occurring between 5-15 mph.

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Old 09-13-2016, 06:22 PM   #29
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Default Re: 1999 SC2 automatic is this normal?

Quote:
Originally Posted by GTS350 View Post
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?
See attached. Note that this IS on one with an intermittent TPS failure though. I just haven't seem to have gotten to it since it is infrequent and I've been busy with another vehicle. But since the part is now on the shelf and I'm thinking about, perhaps I'll do it tonight.
Attached Images
File Type: jpg IMG_0642 (2).jpg (123.9 KB, 7 views)

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Old 09-13-2016, 10:41 PM   #30
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Default Re: 1999 SC2 automatic is this normal?

Try shifting to neutral sometime when you approach a red light or stop sign. That will eliminate the transmission keeping the driveline engaged and "pushing" the engine. You'll still notice the increased idle speed, until you get down very close to 0 MPH. Fdryer describes the emission control logic of this in an above post. He references 5-15 MPH as the drop-off range, but on my car it doesn't drop until about 3-5 MPH.

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Old 09-14-2016, 12:16 AM   #31
GTS350
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1999 SC2
Default Re: 1999 SC2 automatic is this normal?

Quote:
Originally Posted by madpogue View Post
Try shifting to neutral sometime when you approach a red light or stop sign. That will eliminate the transmission keeping the driveline engaged and "pushing" the engine. You'll still notice the increased idle speed, until you get down very close to 0 MPH. Fdryer describes the emission control logic of this in an above post. He references 5-15 MPH as the drop-off range, but on my car it doesn't drop until about 3-5 MPH.
Funny you say this earlier I tried exactly what you said.
I could while slowing down take my foot off the gas and shift into neutral the RPM's will drop to 11-1200 and remain there again until I reach ZERO mph than drop to the correct 800rpm range. There is defiantly something wrong. 5-15mph would be great and I would be happy with 3-5mph but mine is 0mph 100% of the time (I will say it's consistent).

Quote:
Originally Posted by Cheyne View Post
See attached. Note that this IS on one with an intermittent TPS failure though. I just haven't seem to have gotten to it since it is infrequent and I've been busy with another vehicle. But since the part is now on the shelf and I'm thinking about, perhaps I'll do it tonight.
Can you run live data? To see if it's repeating 0 even while car is moving?

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Old 09-14-2016, 07:43 AM   #32
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Default Re: 1999 SC2 automatic is this normal?

Quote:
Originally Posted by GTS350 View Post
Can you run live data? To see if it's repeating 0 even while car is moving?
I don't have the scanner with me. It should read 0% at idle on up depending on the accelerator position. Note that the TPS sweep can be tested without the motor running or moving. Mine seems to do as mentioned around 3-5 mph where the IAC kicks in, but it is not noticeable if not looking at the tachometer. The behavior you describe is NOT normal when you mention having to brake harder/feeling like both the brake and accelerator are being used.

Did you clean the IAC when you did the throttle body? I'm still inclined to believe TPS based on your live data reading.

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Old 09-14-2016, 07:38 PM   #33
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1999 SC2
Default Re: 1999 SC2 automatic is this normal?

Problem solved!
For those who thought TPS........... Sorry it was OK (now I have a spare)
For those who said this was normal.....Really?........ (If your car is doing this get it fixed it's not normal and it's not safe)
For those who like me thought IACV.....ding ding ding
And like Cheyne now my TP at idle is 0.0

Quote:
Originally Posted by madpogue View Post
Fdryer describes the emission control logic of this in an above post. He references 5-15 MPH as the drop-off range, but on my car it doesn't drop until about 3-5 MPH.
5-15mph would be nice to help coast to a stop but I would say your 3-5mph is more accurate at least in my case now. But I can live with 3-5mph it was the 0mph that was un-drivable.

Thanks guys for all the imput.

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