revs. randomly for no reason

[mlizotte]

Shop said adjust idle should fix this problem. Can you even adjust the idle on the engine?
01 buick lesabre

 

[02LTD2.0]

If it's revving up and down you may have a vacuum leak.
As far as I know the idle is controlled by the Idle Air Control valve on the throttle body.

 

[mlizotte]

No it randomly accelerates while driving.

 

[HotZ28]

Check the TPS & EGR also. Do you have any codes? Idle speed is set in the PCM & is not adjustable without tuning!
How To Test The GM 3.8L Throttle Position Sensor (TPS)

How To Test The GM EGR Valve Buick, Chevy, Olds, Pontiac

GM 4.3L, 5.0L, 5.7L Index of Articles

easyautodiagnostics.com

 

[mlizotte]

Check the TPS & EGR also. Do you have any codes? Idle speed is set in the PCM & is not adjustable without tuning!
How To Test The GM 3.8L Throttle Position Sensor (TPS)

How To Test The GM EGR Valve Buick, Chevy, Olds, Pontiac

GM 4.3L, 5.0L, 5.7L Index of Articles

easyautodiagnostics.com

no code shop tech said he would adjust the idle to fix this problem, but you can't. ???

 

[HotZ28]

no code shop tech said he would adjust the idle to fix this problem, but you can't. ???

Like I said, the PCM controls the idle speed. I don't know any other adjustment that would work, unless the shop has a programming PCM device. In addition, does the shop tech think increasing the idle RPM will overcome the random acceleration while driving? I don't think so!

 

[jotzgr]

You might also look at butterfly inside throttle body. Make sure it is clean on both sides, closing all the way, and moving freely without sticking. I had similar issue on two different Lesabres and edges of throttle plate were gunked up not allowing it to close all the way (randomly). Was worse once it warmed up and the gunk got sticky. Seemed like car was taking off on its own at times. All are correct regarding idle adjustment. There isn’t any. Controlled by PCM. I wouldn’t have much confidence in a shop that told you that.

 

[mlizotte]

You might also look at butterfly inside throttle body. Make sure it is clean on both sides, closing all the way, and moving freely without sticking. I had similar issue on two different Lesabres and edges of throttle plate were gunked up not allowing it to close all the way (randomly). Was worse once it warmed up and the gunk got sticky. Seemed like car was taking off on its own at times. All are correct regarding idle adjustment. There isn’t any. Controlled by PCM. I wouldn’t have much confidence in a shop that told you that.

Thanks. I want to clean the throttle plate but there's a screen on the end. Can it be removed?

 

[02LTD2.0]

Yes

 

[jotzgr]

Thanks. I want to clean the throttle plate but there's a screen on the end. Can it be removed?

Use a couple paper bent paper clips or pick tools, one on each side. You want to very carefully hook the screen and pull it straight out. If it gets cockeyed, it will hang up and break into pieces. These things pretty much break just from looking at them, so you have to be very careful. After I saw how they came out, I got a couple out of the scrapyard as spares. Half of those broke while I was trying to get them out. They are not metal, some kind of pressed paper/plastic material. It just presses back in. Do not leave it out. If you really want to have wild throttle variations and idle, try driving with it removed. Ask me how I know?

 

[02LTD2.0]

I had an Olds 88 that had NO screen. It ran and idled fine. If you experience wild variations as described above then you have other issues.

 

[jotzgr]

If you experience wild variations as described above then you have other issues.

It’s documented that GM put the screen there for a reason to provide smooth air flow through the throttle body. I had no other issues. I broke the screen while cleaning the throttle body and left it out. Immediately, had all kinds of weird surges while driving and idling. Got a replacement screen; have never had another issue and it’s been well over a year. Just giving my own personal experience with this, which I realize now I will stop doing from here on out. Never mind my experience owning four 20+ year old Lesabres.

 

[02LTD2.0]

I am speaking from experience as well. I have owned 2 Bonnevilles, 3 Olds Eighty Eights and 2 Lesabres since 2003.
One at a time.
When I buy a car I start with fresh plugs and wires.

 

[jotzgr]

Like I said, I’ll keep my experiences to myself from now on. I am not some shadetree mechanic that doesn’t know what I am doing or just throwing stuff out there. I currently have 12 vehicles registered and insured from 1978 to 2002 (+ 2 additional new ones - 14 total), all of which I maintain myself and do 100% of the work. I have not paid a mechanic or shop for any repair work in over 25 years. I have previously won National Concours Gold for the whole United States for a car I restored and again, did 100% of the mechanical work and restoration. I did pay a shop to do paint and body work, which I don’t do.

 

[02LTD2.0]

Wow.....The original question was can the screen be removed for cleaning and I replied yes. I was not recommending that they leave the screen out.

As far as my experience with NO screen I did not remove the screen. I only noticed it when removing parts from the engine before junking the car due to it being in an accident.