: Engine running at higher then normal RPM`s



limoguy
03-25-08, 09:14 AM
98 northstar deville, 153k miles, runs great. Yesterday, I was in NYC waiting for a parking spot with the car off. Suddenly, I noticed a car pulling out, So, I started my car, shifted into drive quickly and went for the open spot. As I started in motion the car was revving up without pressing the gas pedel. I shut her off once in the spot, then started it again 15 mins later and it was normal again. Last night, im driving on the highway doing 60, then she starts accelerating on her own. So, I pull over, shut it off, restart it and its back to normal. what could this be? a sensor? sticky linkage? any ideas? thanks

Ranger
03-25-08, 10:26 AM
I'd start by checking the linkage and look for a vacuum leak.

limoguy
03-25-08, 10:31 AM
Thanks Ranger..I will take a look myself but will likely let the mechanic check.

tateos
03-25-08, 11:28 AM
Cruise control?

limoguy
03-25-08, 11:33 AM
Cruise control?

I also thought that. I went on a 100 mile run before without the cruise control and she was fine. BUT...when I did some local driving, she was at higher then normal revs. when I shut it and restart it usually goes to normal again.:crybaby:

Submariner409
03-25-08, 11:50 AM
Hiccup in the throttle position sensor ? Multi-pin connector on the rear side of the throttlebody, near the butterfly lever and coil spring. Disconnect and reconnect twice.

limoguy
03-25-08, 11:56 AM
Hiccup in the throttle position sensor ? Multi-pin connector on the rear side of the throttlebody, near the butterfly lever and coil spring. Disconnect and reconnect twice.

Is it visible when The hood is open? is it a small connector? I guess its black ?

limoguy
03-25-08, 12:09 PM
OK...I disconnected and reconnected that plug twice. It had 5-pins all in a row. Hope that was the one. I will try the car soon and see...thanks submariner

tateos
03-25-08, 12:25 PM
Have you ever cleaned the throttle body and valve? That is a common problem and the solution is easy

limoguy
03-25-08, 07:01 PM
Hiccup in the throttle position sensor ? Multi-pin connector on the rear side of the throttlebody, near the butterfly lever and coil spring. Disconnect and reconnect twice.


OK Submariner...Looks like that cured the issue with the high RPM`s. Thanks alot..I owe you a beer!! I love this car. :duck:

limoguy
11-09-08, 07:01 PM
Ok...This is happening again. The RPM`s go up high for no reason. It was fine for months and just started the other day. It doesnt happen all the time though. What should I do first?

Ranger
11-09-08, 08:28 PM
Have you cleaned the TB as suggested?

limoguy
11-09-08, 09:21 PM
I did not. I don`t have instructions to do it. Is it something an average person can do?

limoguy
11-09-08, 09:22 PM
Have you ever cleaned the throttle body and valve? That is a common problem and the solution is easy


I would like to do it. Where do I get instructions?

limoguy
11-09-08, 09:32 PM
OK...I found the thread where it gives specific instructions. I will try it..Thanks

limoguy
11-10-08, 05:27 PM
I cleaned the throttle body, it was real simple...still the same problem. She idles at like 1200rpm...not good....What should i try next...thanks

Ranger
11-10-08, 08:56 PM
Have you checked the codes? Since the TPS seemed to help for a few months (post #10), I would suspect it is bad.

limoguy
11-10-08, 09:16 PM
pcm 0122
pcm 1122



Please give me the exact part name so i know what i need. thanks

If it is the trottle position sensor, where is it located and is it easily accessible? thanks

Ranger
11-11-08, 10:17 AM
P0122 - Throttle Position (TP) Sensor Circuit Low Voltage
P1122 - Throttle Position (TP) Sensor Circuit Intermittent Low Voltage

The TPS (Throttle Position Sensor) is mounted on the side of the TB inline with the throttle plate shaft and is attached to it so as to be able to monitor it's position. Easily accessible.

limoguy
11-11-08, 12:31 PM
Thanks Ranger!! I bought the part and will give it a shot.
wow...thats kinda hard to get at. I think i need longer hex keys.

Ranger
11-11-08, 02:48 PM
:hmm: Just remove the silver beauty cover and it should be right there on the side of the TB as I recall.

limoguy
11-11-08, 05:48 PM
I let the mechanic do it. He had to remove brackets and stuff. I didnt want to get involved. One screw was easy, the bottom one is the the problem. Took him 15 mins or so. But now, the car is running like a charm once again. Thanks so much Ranger!

Ranger
11-11-08, 08:42 PM
Glad to have been able to help and that you have her running good again.

68Futura
07-15-09, 10:00 PM
Hey Limoguy, how did this work out for you? did it ever come back?

I have the same exact problem in my 98 sls. I replaced the throttle position sensor, and it was fine for a month or so, then it came back. Ranger, do you have any thoughts? I checked the wiring the best I could. I haven't cleaned the TB yet, but it didn't seem to help Limoguy when he did that.

Ranger
07-15-09, 10:30 PM
Might try pulling battery power. Also try touching the cables together. If none of that helps, you may need to have the idle learn procedure done.