2003 A4 Misfire on Cylinder 4 (p0304) and EML not lighting up

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Lucas7

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Hi all,

Purchased myself a 2003 A4 1.8T Quattro 190 (126k on the clock) on the weekend and on driving it back it was misfiring in low revs. Got it home and the next morning I got the trusty OBD reader out and it brought up 1 code p0304 - Misfiring on Cylinder 4. The chap I purchased it off said that it had new coils, new spark plugs and a new turbo and that the turbo will need 'bedding in'. I thought this was maybe the issue but the fact that its brought up the code makes me think that thats not correct.

The other issue (which I didnt notice until I got it home) is the EML doesnt light up even on startup. Surely with the misfire it should bring up the EML? I've checked the 4 or 5 fuses which correspond with EML and theyre all fine.

Im fairly new to Audis but reading a lot on the forums it seems to be a coil problem, which have already been done.

Could anyone shed some light on the issues I'm having?

Many thanks,

Lucas
 
Try swapping a coil pack to see if the misfire still occurs on the same cylinder
 
Hi thanks for the reply.

I cleared the code and took it for a 30 mile drive and just got back. It was misfiring like it did on the weekend, I put the reader in and it says 'No codes'. Surely because of the misfire the same P0304 code should come up? I havnt touched the coils yet as I thought it was pointless until a code showed up again. Does it take a period of time for the error code to show again?
 
When you say a reader.........are you using the full VCDS kit or a universal portable diagnostics machine which are okish but no where near as good as VCDS.
 
I've just replaced the coil pack on cylinder 4, took it for a test drive and same problem with misfire and rough idle.

I read somewhere that if you take the MAF out and drive it and it runs better then that could be the problem. I've taken it out and it's still misfiring and the idle is still rough. The only code its bringing up is to do with the MAF, and the EML still isnt working even with the MAF out. It has bought on the ESP light though?

Can anyone suggest where to go from here? For both the rough idle and misfire, and also the EML not working.
 
have you checked the spark plugs?

Turbos dont need bedding in. They also dont cause misfiring.

It could also be a split hose somewhere, so check round the engine carefully to see if any of the hoses have split.
 
Any kind of miss fire is air,fuel or spark related. Start with the easy bits and work back from there,take the plugs out and see if they all look the same, you may also have a dodgy ht lead that may be on its way out causing it to be intermittent with error codes
 
aragorn said:
have you checked the spark plugs?

Turbos dont need bedding in. They also dont cause misfiring.

It could also be a split hose somewhere, so check round the engine carefully to see if any of the hoses have split.
Click to expand...

Hi Aragorn,

Thanks for the reply, being naive I trusted that statement for the turbo but have found out that they don't need bedding in. I'll have a look tomorrow around all the hoses and see if I can see/hear anything. I'll update tomorrow.
 
ruffrida said:
Any kind of miss fire is air,fuel or spark related. Start with the easy bits and work back from there,take the plugs out and see if they all look the same, you may also have a dodgy ht lead that may be on its way out causing it to be intermittent with error codes
Click to expand...

Hi ruffrida,

The spark plugs were only done 2 weeks ago but I'll try check them tomorrow aswell as the hoses as above. As there arnt any codes coming up on my obd reader If I have no luck tomorrow I'll get someone on vag-com to do a scan over the weekend and see if that can bring anything up. And can I ask is it the ht lead which goes into the coil? And how do you know if you've got a bad one?

Thanks.
 
You have a dodgy lead your car will run lumpy or miss fire. If I remember rightly, if you take the plugs out 1 will smell of fuel more than the others
 
*Update*
I've removed each coil pack in turn and started the car and it runs worse when one is removed so I dont believe it to be the coils. Im still getting no fault codes on my obd2. I took the oil cap off and when the car is running there is a heck of a lot of air blowing out through it, could that be anything to do with the misfire and rough idle?
 
Have you done a compression test on the block?

This would rule a lot out if it is fine or point to others if it fails like head gasket, valves etc
 
audi upgrades
No compression test done. I've just had the AA out who have done a full diagnostics on it and it brought up the code for the MAF, im on my way now to collect a new MAF and to see if that cures the problem, he seems to think that thats definitely it. If that fails then ill be getting a compression test done. I know you can clean the MAF but id rather just get a new one to be 100% sure. Ill update this evening to see if that makes a difference! Thanks again for the advice.
 
Sorry bud but not sure that is going to cure it, the AA said i had this problem and that problem, turned out to be something completely different, they are motoway monkeys that will find anyway to get onto the next job, aint found a decent 1 yet that knows what the on about !!

I hope it is for your sake, been in ere, doen that, got very annoyed lol
 
Thanks mate, and you were unfortunately correct. So the next stage is compression test?
 
As mentioned the compression test will answer a lot of questions and is quite quick.
 
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