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Old 07-25-2014, 03:52 AM   #1
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Default 4.2 Misfire, engine shake. ....

Hi
I have 2010 4.2 q7 that has engine misfire, possibly fuel delivery problem,
it start jerking at cruising speed, city driving. Acceleration looks normal, but once I reach desired speed, start jerking. Stop light engine shakes, misfire, check engine light on.

I have change spark plugs and noticed that driver side cylinders burning great (brown dry spark tips), but passenger side are wet and black on all four cylindes, also this side has light smoke at tailpipe, black, like fuel was not burning.

I have swiched 4 coils from driver side to passenger side hoping that misfire will move on driver side, but no change.

Going to change fuel filter....

Will high pressure fuel pump malfunction do that?

Anybody experience this on this engine? I hoping that its not timing chain, for that engine will have to be removed. ....
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Old 07-25-2014, 11:40 AM   #2
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Hook up a scan tool. See what cylinders are missing. See if there are other codes. Your missing a big part of diagnosing it by just pulling plugs and trying to diagnose it like an old 350 with a carburetor.
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Old 07-25-2014, 04:51 PM   #3
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Yea, I am looking for diagnostic tool.
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Old 07-25-2014, 04:51 PM
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