Fast Idle, drives without touching gas pedal

For Olds Aurora and Cutlass to the Alero and Delta 88.
Ask our auto mechanics for help to all your Oldsmobile car questions.
amora

Fast Idle, drives without touching gas pedal

Unread post by amora » Fri Dec 11, 2009 1:56 pm

I have a 2001 Silhouette that sometimes "sticks" on a fast idle and it can drive and increase speed without touching the gas pedal. I can put it in park and shut it down then restart and it will stop it, but can do it again at anytime. I had the throttle body cleaned first...didn't stop it. I replaced the throttle position sensor and it stopped for a few months, but it's right back at it. Any help? Thanks, Andrea

User avatar
TerryAuto
Posts: 313
Joined: Fri Dec 11, 2009 8:48 pm

Re: Fast Idle, drives without touching gas pedal

Unread post by TerryAuto » Fri Dec 11, 2009 9:39 pm

Wondering that the Throttle sensor TPS fixed it for awhile, but it is back.
Maybe there is a wiring problem around the sensor, and changing it moved the wiresto correct the problem for awhile, but not it is back.
i would move the wires around by the TPS to see if you can get it to act up, or correct itself when it is acting up.
Be sure to check the Similar Topics down this page for more help.

amora

Re: Fast Idle, drives without touching gas pedal

Unread post by amora » Mon Dec 14, 2009 8:51 am

I will give it a try...thanks!
Andrea

Dimes

Re: Fast Idle, drives without touching gas pedal

Unread post by Dimes » Fri Mar 19, 2010 2:44 pm

I've been having a similar problem on my 91 Olds 88 3.8 vin c(100K miles). It started with a code 34 which was MAF sensor. I replaced it and in doing so I cleaned the whole throttle body. Check engine light is off and it runs smooth again. But now it takes a few seconds to idle down. If i put it in gear it will idle and pull like normal but once I press on the throttle it tends to keep pulling. It will idle to about 40mph on a straight surface, it wont climb on an incline. Also it doesn't do it all the time, but like 80% of the time. I inspected the IACM and it was in horrible shape and sticking so I replaced it also. This still didn't correct the problem. I then went to a possible vacuum leak and after 2 cans of intake cleaner and a couple rounds I cant find anything. I then tested the TPS with an OHM meter and it looks great. So where else might i look? Ive been told that the EGR valve could be causing problems but the car runs great. Except I'm killing my brakes and gas mileage... Any help is appreciated.

Frustrated in Illinois

Meccboy

Re: Fast Idle, drives without touching gas pedal

Unread post by Meccboy » Fri Mar 19, 2010 9:15 pm

No, i would not think it was the EGR Valve.
Just for the heck of it, disconnect the battery for a few minutes. Maybe it needs to be reset after the throttle and IAC are now clean. Have had this happen on some newer cars.
Also, the TPS tests good and goes thourgh range smoothly? But what is the resistance at idle. Maybe needs to be tweaked a bit. Best to look at sensor data on a scanner. Should be about .40 Volts.

Dimes

Re: Fast Idle, drives without touching gas pedal

Unread post by Dimes » Sat Mar 20, 2010 11:47 am

Thanks for the fast reply ; D. I had a slight dead spot in the TPS so I replaced it. The voltage is set to .4 on idle, 4.5 on FOT, But it seems Its still wanting to high idle. Almost as if something is sticking and not allowing the idle to drop fast enough. Could it be possible for a vacuum leak inside the vehicle to cause this problem, or is it possible to have such a slight vac leak around the motor that spraying chem on it isn't getting enough to see the idle change? I'm going to try to drive it today on the highway and see maybe if it relearns the way is supposed to run. I guess if it doesn't correct itself I'm going to put it in the shop and have them test the vacuum. Ill follow up and let you know what I find. Thanks again for anymore imput on the matter.

Meccboy

Re: Fast Idle, drives without touching gas pedal

Unread post by Meccboy » Sun Mar 21, 2010 1:07 am

Dimes wrote:Thanks for the fast reply ; D. I had a slight dead spot in the TPS so I replaced it. The voltage is set to .4 on idle, 4.5 on FOT, But it seems Its still wanting to high idle. Almost as if something is sticking and not allowing the idle to drop fast enough. Could it be possible for a vacuum leak inside the vehicle to cause this problem, or is it possible to have such a slight vac leak around the motor that spraying chem on it isn't getting enough to see the idle change? I'm going to try to drive it today on the highway and see maybe if it relearns the way is supposed to run. I guess if it doesn't correct itself I'm going to put it in the shop and have them test the vacuum. Ill follow up and let you know what I find. Thanks again for anymore imput on the matter.
If there was any kind of vacuum leak, you should find it by spraying around. Nothing internal i can think of would cause this. Is the throttle mechanically sticking? Maybe the throttle plate shaft is worn out.

Dimes

Re: Fast Idle, drives without touching gas pedal

Unread post by Dimes » Sun Mar 28, 2010 11:21 am

I took the throttle body back off Saturday and completely tore it down again, everything is in perfect shape, all new gaskets. I'm have now noticed if the car is idling high, i get the hood open and try to force the throttle shut and it will idle down, but the plate isn't sticking, and it doesn't really move, just bounces on the low idle screw. I'm only to assume now that the idle screw needs an adjustment, but without tools I'm going to have a local mechanic tune it to spec. Is this common when replacing a MAF sensor to manually adjust the throttle body? And help is appreciated.

Dimes

Re: Fast Idle, drives without touching gas pedal

Unread post by Dimes » Sun Mar 28, 2010 11:25 am

I also forgot to mention that my cruise control isn't working properly. It will allow me to set it and it works, but if i hit the accelerate switch on the turn signal it decelerates. Prior to replacing the MAF sensor i do remember that the acceleration side worked. An employee at the local auto part shop seems to think it could have something to do with it?

  • Similar Topics
    Replies
    Views
    Last post