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4.2 Misfire, engine shake. ....

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Old 07-25-2014, 03:52 AM
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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
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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
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Yea, I am looking for diagnostic tool.
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Old 11-17-2014, 02:49 PM
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Are u using 93 octane? If not you probably have an injector that needs cleaning. Full tank with a bottle and a half of sea foam, go for a long freeway drive @ 80+
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Old 11-24-2014, 03:24 AM
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Originally Posted by C-ked View Post
Are u using 93 octane? If not you probably have an injector that needs cleaning. Full tank with a bottle and a half of sea foam, go for a long freeway drive @ 80+
I did that with 10g fuel and full sea foam bottle, engine looks like runs fine, but check engine is on, im thinking to replace fuel filter, I see youtube video on how to, and not enough fuel flow test that will make engine run ruff, miss fire, if that will not fix it, it may be the high pressure fuel pump on this engine side, since all four cylinders have miss fire.
For now I have to order fuel filter element and see if this help, the oxygen sensors will probably need to be replaced soon too, and I hope cats will not get damaged......
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Old 12-01-2014, 06:47 AM
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Originally Posted by Przemek31982 View Post
I did that with 10g fuel and full sea foam bottle, engine looks like runs fine, but check engine is on, im thinking to replace fuel filter, I see youtube video on how to, and not enough fuel flow test that will make engine run ruff, miss fire, if that will not fix it, it may be the high pressure fuel pump on this engine side, since all four cylinders have miss fire.
For now I have to order fuel filter element and see if this help, the oxygen sensors will probably need to be replaced soon too, and I hope cats will not get damaged......

Fuel filter is easy, Always a good idea to change that. If you've done a tune up, cleaned the MAF sensor, and the sea foam trick, I think it'll be only a matter of time before the cel turns its self off. Do you have a vcds yet to check what codes were thrown? If you're in Tampa I'd be happy to clear them for you.

Last edited by C-ked; 12-01-2014 at 06:52 AM.
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Old 12-08-2014, 03:16 AM
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Originally Posted by C-ked View Post
Fuel filter is easy, Always a good idea to change that. If you've done a tune up, cleaned the MAF sensor, and the sea foam trick, I think it'll be only a matter of time before the cel turns its self off. Do you have a vcds yet to check what codes were thrown? If you're in Tampa I'd be happy to clear them for you.
I Am looking for fuel filter element part number, so I can just replace that instead fuel filter assembly, if anybody knows that please let me know, and where to order.
Like I expect the oxygen sensors need to be replaced, I have scan the engine codes and I got oxygen sensors malfunction, no misfire so far.
I keep running fuel with seafoam.
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