Weak #7 Cylinder
07-03-2007, 10:25 PM
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Weak #7 Cylinder took my car to get tuned today...found out i have a weak #7 cylinder. I didn't notice it before and now i feel like an idiot. im gonna check the basic things tom. i guess...plugs, wires etc. anything else i should look for?
07-04-2007, 02:46 AM
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First of all, no need to feel like an idiot, unless you're a professional engine tuner or an LSX engineer chances are you won't know you have a weak cylinder unless it's misfiring. Now to answer your question, the problem can be a number of things. A partially clogged injector, low compression, carbon deposits (on intake valves), and worn cam lobes(since the no. 7 & 8 cylinders are the last to get oiled) all come to mind. Just out of curiosity, do you know what method the tuner used to determine what cylinder/s are weak?
07-04-2007, 08:25 AM
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he plugged in this computer and he shut each cylinder down individually so i could hear the difference. and when he shut #7 down there was almost no change at all
07-04-2007, 09:28 AM
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Sounds like he ran a cylinder balance test. Fuel is cut to each cyl to monitor the drop in RPMS to determine the relative work performed by each cylinder. It is a decent test for locating problems, but it must be run a few times to try to get consistent, repeatable results. Did the tuner say how much higher its rmps were compared to the other cylinders?
