1994 PONTIAC GRAND PRIX WILL NOT IDLE DOWN

  • Tiny
  • Jay Davis
  • 1994 Pontiac Grand Prix

Engine Performance problem
1994 Pontiac Grand Prix 6 cyl Front Wheel Drive Automatic 160000 miles

For the past few weeks I have had a problem with this car idling at 1600 r.P.M.S It was annoying but drivable. I suspected MAFS sensor or air temp sensor. I cleaned them with carb cleaner spray and now the car will not idle below 2600 R.P.M. Before using the carb spray, I steam cleaned the engine as it was very dirty, then drove it 20 miles home with no problems. I have blown out all connections to sensors with compressed air in case there was water in them. Any ideas where to go from here?

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Wednesday, March 11th, 2009 AT 11:50 AM

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  • Tiny
  • obxautomedic
  • Expert
  • 3,743 posts

Hi Jay,

Check for vacuum leaks and also check the IAC (Idle Air Control Valve).

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Wednesday, March 11th, 2009 AT 12:10 PM
  • Tiny
  • Jay Davis
  • Member

Just wanted to update this, I found a massive vacuum leak behind the throttle body. The tube which ties the PCV vale and the Evap canister to the intake manifold has a grommet built onto it which slips into a hole in the top of the intake. This grommet was gone! G.M. Wanted $30.00 for the tube assembly. I found a $2.00 grommet at Napa which fit Very tight and solved the issue. Also I found the EGR port which is cast into the intake manifold was totaly plugged. I cleaned this out and installed a new EGR gasket, This morning on my 20 mile commute the check engine light stayed off for the first time in years!

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Tuesday, March 17th, 2009 AT 9:52 AM
  • Tiny
  • obxautomedic
  • Expert
  • 3,743 posts

Good Job

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Tuesday, March 17th, 2009 AT 3:57 PM

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