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Old 12-13-2002, 08:37 PM
Senior Member
Join Date: Sep 2002
Location: New Jersey, U.S.A.
Posts: 2,398
I'm not exactly sure what you mean by "lumpy". If the idle is slightly rough, then I think checking the injectors should be considered. Most idle air valve problems will result in an incorrect/fluctuating idle speed. Check the "Llambda" before you go any further. This is a good way to determine if you have a rich or lean condition. I've seen a few 116/117 engines that develop vacuum leaks at the rubber boots that seal the upper and lower sections of the intake manifold. Keep in mind that there are many vacuum leaks possible, so check the easy stuff first. As you said , the ignition system is good to go, so look carefully for vacuum leaks. Other things worth checking if all else fails: 1. Carbon build-up on intake valves(you can check for this if you remove the injectors). 2. Cylinder compression(It's free if you do it yourself, and it's conclusive). 3. Timing chain stretch. Good luck
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