Question about 1991 GMC Sonoma

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High idle Truck Idles high in between gears, and when sitting. Once in a while it will kick back to normal idle, but mostly its high. Dang thing increases speed without gas in all gears

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  • GMC Master
  • 2,431 Answers

Time for a IAC (idle air control ) motor
high idle - 1_22_2013_5_31_57_am.jpg

Posted on Jan 22, 2013

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  • 2 Answers

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Posted on Jan 02, 2017

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  • 2 Answers

SOURCE: Truck keeps stalling

you have a leaking manifold gasket

Posted on Dec 08, 2008

  • 58 Answers

SOURCE: 1995 gmc truck bucking

Or a bad distributor cap

Posted on Dec 21, 2008

SOURCE: Idles rough upon start , goes dead when letting up on gas.

If the bat went dead and was disconnected it can take 25 to 50 miles of driving for computer to reset sensors and controls. Sounds like MAF Sensor maybe reading different than when it was first driven. Did you drastically change climates or altitudes, New readings from when it originally was put into service. Slight changes in temp, alt and other variables gradually reset, if driving does not improve within 50 miles it will need diagnostics.

Posted on Jan 06, 2009

  • 373 Answers

SOURCE: starts rough

try the plugs plug wires and cap and rotor

Posted on Feb 07, 2009

  • 169 Answers

SOURCE: fan speed high, idles eratically

theses are known for bad fan clutch also needs poss pcm update

Posted on Aug 29, 2009

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Related Questions:

1 Answer

Idles to high & will not change gears right.


Clean the throttle body and map/maf sensor.

Sep 03, 2017 | Cars & Trucks

1 Answer

My van is idle high i cleaned the throttle boady and it idle down the a few hours later its high idle again why i replaced two sensor and still idle high


Hi Alexandra, Im AL the owner of Big As Auto Repair

There are several things that can cause high idle, but the 2 most common problems are as follows.

(1) You could have a vacuum leak somewhere on the engine. Here is how to check for that issue. Here's what I want you to do: Buy a can of CARB Cleaner and while the engine is running spray around the Intake Manifold, the manifold is the thing the throttle body sit on. Also spray around all the vacuum line as well. If while spraying there is a change in the idle speed then you have found your leak. If there is no change then move on to step 2.

(2) Sometimes when you have a high mileage vehicle parts begin to ware out or can also begin to stick in place. Here something you can check. Idle Air Control Motors can start sticking from corrosion build up and can cause a high idle issue. Here what I want you to do. Start the engine and let it idle, while its idling I want you to tap on the Idle Air Control Motor If it idles down to normal idle speed replace the motor. The motor mounts onto the throttle body and most of them are round. Once you replace it and start the engine you'll notice that its idling real high, :This Is Normal, just let it idle until the engine controller resets the idle speed to normal.

Hope this helps and should you need further help please visit my auto repair website. http://www.bigasautorepair.com/

May 25, 2015 | Cars & Trucks

2 Answers

I have a 1989 Mazda 323, when cold engine idles very high, when very cold it idles so high that rev limiter kicks in, and it revs up, limiter kicks in, revs up limiter kicks in, once it warms up idle drops...


Have it looked at by a dealer,iam not sure here but i think you have a vacumn leak like the feed pipe to the servo split but really you need a mechanic who works on these cars day in day out and they will go straight too the problem for you

Jan 18, 2015 | 1989 Mazda 323

1 Answer

Idles high from first to second gear .


Define idles high like its going high rpms before shifting or the engine itself is high reving if its high rpming when shifting its mostly you tranny going out you can try tranny fix oil I used it on my truck when it had shifting problems and ive had no problems since it takes a few days to work though and if its the motor itself it could be a lot of things but I dont know much of the problem based on what you told us

Mar 10, 2014 | 2004 Hyundai Elantra

1 Answer

My truck idles high at times then at other times it runs normal rpm


Have you cleaned the idle air control valve? If not i would start there.

Feb 17, 2012 | 1996 Chevrolet S-10 Pickup

1 Answer

While driving car has trouble shifting into gear , and when parked it idles to high.


Make sure high idle linkage is allowing it to kick down after it warms. otherwise back out idle screw.

Jul 25, 2009 | 1984 Oldsmobile Delta 88

2 Answers

Idles too high


This is fairly normal on most cars. It is like the choke. When choked, the idle raises up to increase the internal temperature quicker. Also helps free friction of parts due to the cold. Idle is adjusted by the cars computer and o2 sensors.

Jul 10, 2009 | 1998 Mazda MPV

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