1999 Grand Am 3400 idle problem after flood

Asked by Jul 25, 2010 at 02:51 AM about the 1999 Pontiac Grand Am 2 Dr GT Coupe

Question type: Maintenance & Repair

I was recently in a flash flood with my 1999 Grand Am GT with water reaching the ram air I believe, but only for minutes after stalling out. After working on the car for hours we finally got it to turn over and run(luckily it was not hydro locked) after pulling the plugs and cranking(no water shot out only mist) then replacing them and it eventually started but will not idle at all. The idle was low(600ish rpm) before the flood issue, but stayed running. Now it will turn over and run fine but if I don't leave my foot on the gas it will stall. Also if I hold it down it peaks at 4000 rpms and drops and repeats but never passes 4k.

I immediately changed the oil and filter after getting it running(planning on doing it again in 50 or so miles), added fuel injector cleaner to the gas, removed the air filter to dry(tried it with air filter in and damp but still ran exactly the same) and have run it on the highway once to about 70 mph to try and "blow it out" as was suggested by the person who helped me get it running. I am lost as far as newer car mechanics/computers are concerned and am unsure how to adjust idle on it. If I could get it to run a few hundred rpm's higher there would be no issue at all. Any help/suggestions would be greatly appreciated as this is all I have and with the economy the way it is, there is no new car in my future sadly. Thanks in advance.

1 Answer


MAF is dirty. Contaminated Mass Air Flow sensor will alter air flow readings and adversely effect drive-ability. You don't want water trapped in any vacuum hoses or other sensors either. IAC controls idle speed if everything else is in place. Throttle position sensor could do it as well.

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