: high idle



cadi-nrth*
04-13-04, 07:40 PM
my cadi has a high idle 1500 rpm -had pep boys change out the crank pos sensor closest to the ground - i think its crank sensor B- but it still has a high idle- dash display is broken so i could not pull codes . any suggestions before paying someone to pull codes (for around $80 dollars). i was thinking that maybee they changed the good one (crnk sensr)and left the bad one in? any helpfull :bonkers: comments would be much appreciated. thanks

BeelzeBob
04-13-04, 11:25 PM
Lots of things can cause a fast idle....although I wouldn't suspect a crank sensor right off the bat...why did you replace that?? Was there another problem with the sensor or was it just a shot in the dark??

Is the idle speed control motor working?? That is the first thing that I would suspect regarding idle speed being too high. Look at the throttle lever on the throttle body. There is a small canister shaped device there with a plunger that acts on the throttle lever to control the idle speed. Watch the ISC motor plunger while someone turns the key on and then off without starting the engine to see if it moves in and out. If not it may be failed and the ISC motor may need to be replaced.

If the ISC motor moves it may still be failed as there is another switch inside the plunger (the closed throttle switch) that needs to function for the ISC to work correctly. The ISC motor is controlled by the PCM that sends signals to the ISC motor to raise or lower the idle speed depending on the RPM the PCM sees.

You can try to check the ISC motor by holding the idle slightly high by holding the throttle lever open with your hand to elevate the RPM at idle. With your other hand depress the plunger on the idle speed control motor firmly. It should start to retract. Let it retract fully until it stops. Disconnect the wire to the idle speed control motor to "freeze" it in position. Let the throttle return to idle with the plunger fully retracted. There should be about .030 clearance between the plunger and the lever and the engine should idle down to about 450-500 RPM. If the motor will not retract doing this it is likely failed and needs to be replaced. If the ISC motor fully retracts and there is no clearance between the plunger and the lever then possibly the plunger needs to be adjusted or the motor is just failed and will not retract. There are many options here to explore...but....a better guess for the problem would be the idle speed control motor...not the crank sensor.

cadi-nrth*
04-15-04, 07:52 PM
I checked out the idle position motor and found that it does not move when the key is turned. I also found that it made a lot of clicking noise which sounded very un healthy for a position motor. I was wondering where I would get a replacement - parts recycler(junk yard) or maybe a GM dealer. Does anyone know how much the motor will cost? Thanks to your advice I now belive I found the cause of the high idle. :) Oh yeah/ I had the crank sensor changed because the guys at the shop told me that it was leaking oil, I was thinking that they could possibly just change the o ring but I guess that was not a option.:hmm: I called to find the price at pep boys for the idle motor but they said its not showing up in the computer so I guess Ill have to call around for awhile. Thank you for all your help.

Lawrence
04-16-04, 12:44 PM
Think a new GM part is about $140. At a junk yard, ???, $5.00.

BTW, too late now but you can buy the CPS seal seperatly, from GM. About $4.00.

BeelzeBob
04-16-04, 02:58 PM
Or just use a little dab of RTV on that crank sensor......virtually free.