P0304 Misfire problems

[Ash_89]

Morning guys

recently noticed a misfire on my car noticeably worse when cold starting
the only code im getting on my reader (not vag com) is the P0304 misfire cylinder 4

my injectors where cleaned/serviced last October also new BKR7EIX plugs fitted at the same time , and walnut carbon clean

bits i have tried
swap coil pack and spark from cylinder 1-4 yesterday
replaced pcv pipe (going to inlet) as was slightly leaking
fuel filter changed 1/08/20
r8 coil packs around a year old
the car runs fine whilst driving boosts as normal its only on idle i get the misfire .

engine code BWJ
75K miles



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CYLINDER 4 PLUG

[Ash_89]

Compression test was done last night

cylinder 1  182 psi
cylinder 2  178 psi
cylinder 3  187 psi
cylinder 4  187 psi

will be doing another this weekend with a leak down test aswell due to me using a fair bit of oil

[mjmallia]

When was the cam chain and tensioner changed?

Had a similar problem recently with a cold misfire and had a little chain rattle. The chain and tensioner were changed recently, but one of the three cam plate seals was broken and not producing enough oil pressure at idle.......so the chain was slack and created the misfires.

[Ash_89]

When was the cam chain and tensioner changed?

Had a similar problem recently with a cold misfire and had a little chain rattle. The chain and tensioner were changed recently, but one of the three cam plate seals was broken and not producing enough oil pressure at idle.......so the chain was slack and created the misfires.

Not had the cam chain replaced mate just the cambelt last year , was yours only missing on one cylinder ?
my car does sometimes have a rattle when starting but it goes in a second

[mjmallia]

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

[Ash_89]

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

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]

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.

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 


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.

[Ash_89]

Totally wasn't expecting it to be that bad already lol , il be getting a fresh set of bkr7eix spark plugs this week im pretty sure it couldn't of been doing the plug much good with the misfire

[mjmallia]

I did the same after my misfires and inlet/injector cleaning.....runs like a dream now.