1999 PONTIAC GRAND AM BASE IDLE SPEED ADJUSTMENT

  • Tiny
  • briangiglione
  • 1999 Pontiac Grand Am

Engine Mechanical problem
1999 Pontiac Grand Am 4 cyl Front Wheel Drive Automatic 85000 miles

What kind of tool is needed to adjust the base idle speed and is the adjustment done from the top or bottom of the adjustment screw?

Thank you in advance.

Brian

Monday, March 31st, 2008 AT 4:17 PM

6 Answers

  • Tiny
  • mastertechtim
  • Member

That adjustment screw never needs to be adjusted. What are the problems you are having? Most idle concerns are caused by a idle air control valve issue

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Monday, March 31st, 2008 AT 5:05 PM
  • Tiny
  • briangiglione
  • Member

The problem is a slight shake felt on the steering wheel at idle speed with the transmission in " Drive" mode. An increase of 100 - 150 RPM removes the slight shake. The idle speed is now at 350 - 450 RPM in this condition. Raising it to 450 - 500 removes the shake. The screw top looks like an allen head but there is a center steel piece preventing an allen from adjusting it. Thank you again in advance.

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Monday, March 31st, 2008 AT 5:16 PM
  • Tiny
  • mastertechtim
  • Member

The idle is automatically controlled by the computer, what I think you are feeling is a grounded out engine mount. Very common. This engine mount is at the rear of the engine on passengers side. I replace them all the time for a vibration at idle in drive.

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Monday, March 31st, 2008 AT 6:44 PM
  • Tiny
  • briangiglione
  • Member

There are three mounts. Two on the transaxle front and rear, I replaced the front and inspected the rear, and one on the engine on the p/s upper mid section which I inspected also and is in good shape. When I manually hold the rpm up 100 - 150 rpm, the vibration is gone. I have manually shimmed the throttle cable to keep this rpm and test ran the car and all was great. I could drill out the idle stop tha's in there if it's not adjustable and top in an adjusting screw. Wha do you think? Thank you again in advance.

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Monday, March 31st, 2008 AT 8:21 PM
  • Tiny
  • mastertechtim
  • Member

The one on the pass side upper mid section is the one in question. Humor me. Have it in drive in idle and try using a pry bar to move engine so the pressure is off this mount and tell me if the vibration goes away because I bet it does.

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Monday, March 31st, 2008 AT 8:35 PM
  • Tiny
  • briangiglione
  • Member

I will try that tomorrow or wed and let you know. Thank you.

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Monday, March 31st, 2008 AT 8:37 PM

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