Question about 2002 Pontiac Grand Prix

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I have a 2002 Pontiac Grand Prix GTP. One and a hlaf years ago had the MAF & EGR valve replaced, 1 month later another MAF put in. Two weeks ago I had MAF put in as engine light came on, drove 20 miles and it shut off. Had it towed as it would start and shut right off again and they said it was a defective MAF...again. Engine light came back on next day and it ws the intake manifold & gasket...had them replaced. Engine light came on yesterday on my way home, I made one stop and could not get the car going again...same thing. Had it towed again and it is now at the garage. What could it be? It doesn't seem to be giving any other signs or starts right up but stalls out instantly and quietly. I haven't driven it for a week , but it seemed to feel to me as if it had a little less power upon acceleration. PLEASE HELP ME !! Dawn

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Hi Dawn.

I don't believe that your MAF has ever been the root cause of the problem to begin with. They don't often fail on their own and especially after only a month. If it is due to an electronic problem then it will be instant. The only other cause is the MAF getting so coated with debris or chemicals that it makes the diodes break. It can get dirty from ineffective air filtering or from getting carbon buildup. Seeing that you needed to have the EGR valve replaced, carbon buildup could be a likely cause. It is a common cause for failure of an EGR valve and simply replacing it won't clean up what's left elsewhere in the system like the throttle body...right where your MAF is mounted.

Here is what I want you to do with your car. Do not take it back to the same garage for any of this, you can easily do most of it yourself. They apparently don't know or don't care anyway, get it out of there or give them specific written instructions what to do with it.

Remove the air intake box and throttle body inlet duct and clean it. Remove throttle body. Clean the throttle intake plenum and bore inlet until absolutely spotless. Replace throttle body gasket with an oil-impregnated one that is trimmed back to fit slightly larger than the throttle opening and DOES NOT have the cutouts for the coolant paths. Next, remove the MAF. Clean it with isopropyl alcohol, WITHOUT pressure such as with an aerosol can. It will bend or break the diodes. Allow to dry.
Remove the IAC valve from the throttle body. Clean it, replace the gasket if worn. Use a toothbrush if it's very dirty, I suspect it is. Do the same thing to the mounting hole for the IAC valve. Clean the throttle body bore and plate, from both ends until spotless.

Mount throttle body back on to new gasket. Replace PCV valve.

Replace all spark plugs with copper core Autolite 605's. They are one heat range cooler than stock; it will help your GTP run better especially on those hot days.

Then run only premium fuel in it. I recommend Shell 93. The brand is recommended; high octane is required.

Posted on Apr 23, 2011


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