Questions and Answers

Monte Carlo Idle Problem Q. I have a 1996 Chevy Monte Carlo with about 135,000 miles. Recently the car started over heating but not in the red zone. I started to get a coolant loss and found it had coolant in the oil. I found I had a blown intake gasket. Before replacing it I cleaned the upper and lower intakes in a parts cleaning tub.

I also cleaned the top of the engine with mineral spirits (after I had drained the oil) and put about a gallon of mineral spirits in the oil pan overnight. I then drained the mineral spirits out and let it air out for several hours. I put new oil in and it has shown no signs of coolant contamination since the repairs.

My problem is since fixing the problem the engine will idle will go up and then down. The other day the RPMs started to drop to almost dying when it is idling but the car runs find when it is at operating speed. It seems to only do this fluctuating of RPMs when it is idling. I took off the ERG valve and cleaned it out but am waiting on the gaskets to come in to replace it.

I didn't replace the gasket on the ERG valve tube, which is attached to the lower part of the intake where the EGR Valve is attached, so I figured I had a vacuum leak there. I have not been able to find any other vacuum leaks. The ERG valve did have some carbon it in so I cleaned it out and took it to a local parts place to be checked. The valve is working. They told me I may have fixed it by cleaning it. Could me not replacing the gasket the first time caused the fluctuation in RPMs like that or do I have another problem. What do you think? Can you help?

Thanks,
Larry

A. Did any sensors happen to get submerged in mineral spirits? Some of these later cars still needed to have the idle learned. Start it up with the parking brake on and put it in drive Let it run until coolant fan comes on. Then shut it off for 15 seconds and repeat. If you suspect a vacuum leak you can lightly spray carburetor cleaner around any suspect areas and it should affect idle quality.

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