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John
John, ASE Master Technician
Category: VW
Satisfied Customers: 608
Experience:  ASE Certified Master Technician, ASE Certified Service Consultant, 22 years professional experience
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2002 VW Jetta: multiple cylinder misfires..O2 sensors..accelerate

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2002 VW Jetta code
           P0300 multiple cylinder misfires-- have replaced both O2 sensors with no help.
no other trouble codes--what could do this as it stumbles whenever trying to accelerate--thanks--T

Hello

 

Ignition coils are a very common failure on these cars and likely what is wrong with yours. I would suggest replacing all 4 coils and the spark plugs as the most likely fix. Without a little more information which will require some type of scan tool this is my best guess.

 

Good Luck

John

Customer: replied 7 years ago.
I had replaced on coil about 6 months ago but isnt it very unusual for all four coils to go out at once-- it seems to me that the distributer or part sending the sparks to the coils would be more likely--- - I know coils are $70. each and have just replaced the O2 sensors for $300 that had no effect. I have scanned it and got the P0302 code and then multiple cylinder misfires codes but about three weeks ago had a bank one o2 sensor code so that is why I replaced them.. Could this be something like a plugged fuel filter or distributor problem with no other codes showing--- this started with a slight miss when cold and then after comming off the freeway was missing badly and got home and let it cool and ran some premium thru it and it went back to the one miss sometimes until now it had missed in all cylinders but idles OK misses only when pressing on the gas---T

Which cylinder got the new coil? Also, have the plugs been replaced recently as part of this problem? I didn't know about the o2 sensor code, was it a p0171?

 

Thanks, John

Customer: replied 7 years ago.
It was #1 cylinder that the coil went bad. Did get the P0171 code a few weeks ago and reset the code and havent gotten it since. Now with the miss and then missing on all cylinders codes I am where I am now. Plugs changed about 5000 miles ago when coil was changed

Ok. You could try swapping coils between cylinder #1 (the new coil) and cylinder #2 (misfire code p0302) and see if the misfire code becomes p0301 (cylinder #1). There is no distributor on your car, the coils are triggered by the engine computer. It is not uncommon to have multiple coils fail near the same time, I would always recommend replacing all 4 coils at the same time, except you have replaced one so just doing the other 3 would be ok. I suspect you have other coil problems since you are getting

p0300 (multiple random misfire - cylinders not identified). But the p0171 could either be a vacuum leak or possibly a bad mass air flow sensor (another common failure on these VW's). Replacing the fuel filter can't hurt and it is not very expensive, I would recommend that anyway. It is difficult to diagnose around worn or old tune up components. Finally, check the grounds for the coils. The brown wires bolted to the valve cover are the grounds, make sure they are clean and tight. Let me know how this turns out for you.

 

John

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