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High RPMS and Cruise Control

edited November -1 in Repair and Maintenance
I'm worried about my beloved 02 Toyota Rav4. She's been a great car, we've driven all over the continent, never had a mechanical problem. Lately, particularly on humid days, my cruise control will stop working mid-trip and at the same time the RPMs start running high, nearly twice what they usually are. It lasts until I get home, next time I start her she's fine. The guys at the shop never find anything. The engine control module was replaced last year under an "extended warranty." Didn't help.
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Comments

  • edited March 2011
    [b][i]" . . . . time the RPMs start running high, . . . "
    The Engine Actually Runs At A Higher RPM (Revs Up) Or Just Indicates A Higher Value ?[/i][/b]

    CSA
  • edited March 2011
    Both. I hear the revs, and the gauge indicates a higher value. At 40 it's usually indicating 2000 RPMs. Suddenly, the cruise will shut off (cruise light remains lit, but no cruise control) the pitch of the engine increases, and it's up to 4500 RPMs.
  • edited March 2011
    If the RPMs suddenly shoot up to a much higher level, but the speed of the car does not increase, then it is fairly apparent that you have a transmission problem.

    One possibility is that the transmission is downshifting to a lower gear--probably second gear.
    The other possibility is that there is excessive slippage in the transmission.
    I strongly suggest that you get the car to an [u]independent[/u] transmission shop (NOT to a chain place like AAMCO, Lee Myles, Cottman, Mr. Transmission, etc.) for assessment.

    I am assuming that your Rav has automatic transmission. If it is a manual shift car, then it sounds like you have a slipping clutch. Either way, this needs to be rectified before you wind up stranded.
  • edited March 2011
    It is automatic, but the issue isn't in the transmission. I've had it checked three times in the last year in two different shops; once at the dealership, twice by a reliable, independent mechanic. They all tell me I'll get another 100k miles out of it.
  • edited March 2011
    If your mechanic is convinced that the problem is not connected in any way with the transmission, please ask him the following question:

    [i][b]Why does the speed of the car not change when the engine's RPMs suddenly go from ~2k to ~4.5k?[/i][/b]

    I would be very interested in hearing his explanation. Perhaps we could all learn a few things from him.
  • edited March 2011
    What happens first?
    Does the engine rev faster, and then the cruise control turns off?
    Or does the cruise control shut off first, and then is followed by the high revving?

    If its the first, where the engine revs faster, and then the cruise control turns off, is this happening when you are climbing a big hill?

    Most cruise control systems will turn themselves off if the car climbs a hill, but loses 10 mph. So basically, as the car starts climbing the hill, it will first try to downshift into a lower gear, causing the high revving, but because the engine isn't powerful enough for this hill, the car drops from the 65 mph that you had the cruise set on, to 54 mph, and then the cruise control turns off.

    There is no actual problem with the car in this instance, except that the car doesn't have enough power for the hill.

    BC.
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