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Thread: Faulty MAF (I think)

  1. #1
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    Default Faulty MAF (I think)

    Hi

    I have a 53 plate 120 SRi 1.8L, I think the MAF is faulty, but can't be 100% sure. I got a 0170 code (fuel trim) that caused the emissions light to sometime come on, then it would go off after a fill. Eventually, it stayed on permanently.

    The exhaust was blowing a bit (broken flexy), which seemed to cause a bad idle & jerkiness between 2 & 3K. Got the flexy changed & it seemed OK for a while, but the idle problem returned & it drinks petrol.

    Only code was 0170.
    I changed the plugs & cleaned the throttle body with carb cleaner.
    Gave the MAF a blast of carb cleaner also.

    Still having the bad idle problem, it sounds like it's running on 3 cylinders.
    Stumbling, feels like it's about to cut out when stopped at lights. Also has no power & intermittent jerking during acceleration.

    Found a lot of MAF info here, decided to test the MAF with a voltmeter.
    Seems to be little or no voltage out when idling.

    I disconnected the MAF from the airbox & if I put my hand over the MAF intake, the idle improves & I get about 1.1 volts on the voltmeter.

    I would have expected the MAF to put out more voltage as the air volume increases, not when the volume is reduced. This leads me to suspect the MAF is faulty.

    I've disconnected the MAF & will see if it makes a difference over the next few days.

    Anyone know what the MAF output voltage is supposed to be when idle?

    Gerry

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    Regular Member Ben50n's Avatar
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    Have you chcked your coil packs? You could have one coil braking down? Best have it checked by a garage.

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    Quote Originally Posted by Ben50n View Post
    Have you chcked your coil packs? You could have one coil braking down? Best have it checked by a garage.
    Drove to work this morning (12 miles) with the MAF disconnected. No problems with rough idling or jerking/hesitation, completely different car to drive now.

    Will reconnect the MAF tomorrow. It's looking very like the MAF is the culprit.

    Gerry

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    Running way better with a new MAF, acceleration is back to usual.
    EML light went off by itself a few days later.

    Replacement MAF was a VDO part, not the after market ones.

    Gerry

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    Regular Member suj786's Avatar
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    I've been having the same problems with my 1.8 too. I've taken it to a garage who done diagnostics and said its a faulty EGR.

    Might take apart all the sensors etc and give everything a good clean today. see if anything makes a difference. Did you try cleaning the MAF and what did you use ?

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    Quote Originally Posted by suj786 View Post
    ..Did you try cleaning the MAF and what did you use ?
    Used carb cleaner on the MAF, but it did not fix the problem.
    New MAF (genuine part) sorted the problem.

    Sometimes cleaning will help, if the problem is oil or dirt on the wires.
    I think the electronics in mine were defective so cleaning would not help.

    Gerry

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