Bloody misfire ?

[S666]

Hi folks,

This is my first time posting and I have very little mechanical know-how. But here goes..

So I have a MK5 GTI 07 plate. She’s d-catted and recently has developed a horrendous misfire ?

so when it was originally VCDS it had
️ Voltage supply relay for engine P3087
️ Bank 1 fuel regulator
️ Boost pressure regulator
️ Mass airflow g70

i don’t have the actual codes for them as I was just told the issue ? but I’m getting it rescanned today so I can update with codes.

so I’ve got a new battery and MAF I’ve also got a new filler cap and dipstick as neither were fitting properly anymore.
Still no difference.
I did the home test to see if the PCV was faulty and it appeared to be working fine.

the misfire is constant at this point, fuel is being used like mad. I’ve also noticed a milky residue u see the filler cap. I am only doing very short journeys at the moment though due to not wanting to put the car under anymore strain.
The coolant is going down at a normal rate and is still nice and pink.
I’m wondering if there could be a fuel issue?
ive checked the coil packs andspark plugs and all appear fine..

And ideas or advice would be greatly appreciated ??

 

[3carmonte]

This may not be relevant but look it over...https://www.golfmkv.com/forums/index.php?threads/ignition-coil-spark-plug-problem.196127/#post-3842012
RE: "I’ve also noticed a milky residue u see the filler cap " Would that be your oil filler cap? We used to call that "Making milkshakes" (moisture/coolant in the oil)?

 

[ROH ECHT]

The codes will help. If Misfire codes 300(generic misfire code) with 301 through 304(for all cylinders) appear, this usually means; the cause is other than spark or fueling because it is rare that all four injectors, plugs, or coils go bad at the same time. So the solution is going to likely be a failed PCV or air inlet or vacuum issue. It may also be a timing or timing sensor problem. Some of its codes may be related the the low battery/poor connection issue.

 

[S666]

Hi folks,

sorry for the delay, family life and all that ??

so the codes I have are

️Random/ multiple cylinder misfire detected - p0300 001
️Cylinder 1 misfire - p0301 001

So since my post, we have moved the coil packs around to see if they were faulty, all worked fine. Tested the spark plugs which at that point appeared to be the problem as the one in c1 was knackered.
Since then I have changed the plugs to no avail.
I have compression tested the cylinders as well, which was all hunky dory.

I then scanned it today and got the above codes.
My next move is to speak to an auto electrician as we suspect it could be wiring loom/ecu related.

Has anyone got any other ideas?

 

[ROH ECHT]

So, it is misfiring in #1 cylinder only.
Which plugs exactly were installed? What was the preset gap?
I typically find a coil does this. Coils do fail at a rate and will cause misfires occasionally rather than all of the time. Cleanliness for ground/earth is also important. No oil in the plug wells when plugs are installed etc.. Although rare, I have seen where someone didn't notice a plug washer remained in the plug well when they removed a previous plug and installed another plug on top of it...so, having two washers in there.
It can be the #1 injector, but always good to sort the plugs and coils first. As I said, misfires in all cylinders usually is due to some other factor than plugs, coils, or injectors.

My suggestion, first purchase 5 coils. Install four of them and keep the spare should you see a misfire in one cylinder in the future. I always keep one new coil for just this. Or, to see if it is just a coil, purchase just one new one and install it into the cylinder you see the misfire.

You may find damaged wiring in the coil harness/loom, but if not, and it has good plugs and coils, then it is likely the injector. But with that, you'll want to look at its fuel trims and lambda. It may be cutting back or adding fuel due to a clogged or open injector. Unfortunately, fuel trims and lambda data doesn't narrow down to one cylinder. But it may point to a condition of too little or too much fuel being seen by the B1S1 sensor.

 

[3carmonte]

Do you trust the fuel you're using?