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2000 Malibu 3100 surging idle problem

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  • 2000 Malibu 3100 surging idle problem

    Bought the car with a botched LIM job and 59K miles. Had a milkshake engine. Replaced heads, gaskets, AC Delco OEM plugs, new plug wires, cleaned throttle body, general tune up & fluid services, etc. I have driven the car for 10K miles.
    2 problems persist. First (which I don't feel is related to the surging idle but I thought i should mention) is the CEL is lit with an evap emissions code. Purge solenoid replaced & vent solenoid checked as well as a new OEM gas cap. The previous owner who botched the intake job by loosening head bolts is the same one who replaced the fuel pump on a dirt floor with jack stands. My guess is something he left disconnected or broken with the fuel pump connections. This comes from from finding things like the purge solenoid hose connection found broken in the engine bay but duct tape holding it together along with my 3 trips to the salvage yard for misc missing hardware and brackets like the one that holds the MAP sensor. I also replaced the MAF sensor dues to physical damage. I used a reman AC Delco unit. I have never dropped the fuel tank to see if my hunch is correct.
    Second problem is a periodic surging when stopped at idle at a light, in gear, foot on the brake usually one or two times during a stop light and sometimes not at all. Car surges periodically with a small increase in RPM of just a needle width on the tach. I have been unable find a consistency related to hot/cold/AC/ or anything else. Otherwise the car runs fine.

    Any suggestions on where to check next would be appreciated.

  • #2
    Well, 13 days and no replies... Guess I am still on my own.