All Things Mk5 > How to Guides / Troubleshooting

P0304 Misfire problems

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Ash_89:

--- Quote from: mjmallia on September 04, 2020, 10:00:05 am ---It did to begin with then spread out on three cylinders.

The cam chain does need checking and they can start to fail from as early as 60K miles, but between 80K-100K they are usually due these days.

I don't get any rattle at start up on mine

--- End quote ---

Cheers mate

I did change the fuel filter recently due to a major misfire ( fuel the came out the filter was very dark ) ,im thinking due to there being nearly 30 litres in there i may have just wrecked a brand new filter when i should of drained the bad fuel
the car ran perfect after that for a couple of days

pudding:
Could be the injector.  Maybe carbon fouled if the engine is using a fair bit of oil.  The ECU does a weird double injector pulse when cold to heat the cats up or something.  Maybe injector 4 is a bit lazy.   They do usually clear up with a bigger duty cycle, hence why it's fine on the move.

It is a classic failure on these engines, well, direct petrol injection in general actually.

Ash_89:

--- Quote from: Pudding on September 05, 2020, 12:35:19 pm ---Could be the injector.  Maybe carbon fouled if the engine is using a fair bit of oil.  The ECU does a weird double injector pulse when cold to heat the cats up or something.  Maybe injector 4 is a bit lazy.   They do usually clear up with a bigger duty cycle, hence why it's fine on the move.

It is a classic failure on these engines, well, direct petrol injection in general actually.

--- End quote ---

cheers for the input mate , yes im thinking more towards injector now as well ill be taking them out and swapping 4 to 1 to see if the missfire moves
the joys of direct injection :) 

Ash_89:
Took the inlet of at the weekend to inspect the valves and injector (cyl 4)




also gave the throttle body a good clean being a tad cruddy




the offending injector  :fighting:


The inlet valves were surprisingly covered in carbon/vapor deposits (inlet walnut blast done 9 months ago) too be honest i wasn't expecting them/ looking this bad already


inlet plates just as bad


everything was cleaned also fitted new:
*pcv gasket
*bottom pcv pipe
*inlet gasket
*injector
*cam follower checked
*vac pump o ring replaced

She now runs great no misfires :)



Next job will be to clean the filthy thing

mjmallia:
Good to hear.....it is amazing how quick it builds up.

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