Intermittent Misfire/Rough Running

[JTI]

Did you check for carbon build up on the intake valves?

No I haven't and I doubt it has been checked by previous owners either. Removing the manifold etc. to get to them is probably beyond my skills tbh but that is a good idea and I will look at trying some cleaner first to see if it makes any difference.

I would be inclined to change out the cam follower asap to rule that out and also change the PCV (relatively cheap) to rule that out.
Otherwise, were the new coil packs genuine VW, could there be a fault with them?
Mileage seems relatively low for injector issues but could be...

Yeah I didn't really want to send the car into the garage to get the follower replaced in the state it's in, but it's looking more likely that I will need to.

Problem started before I changed the coil packs and changing them didn't make any difference so I doubt it's them. PCV valve was changed last year, so I doubt it's that either but thanks for the suggestions.

[muff1991]

It will be worth checking for vacuum leaks, boost leaks, PCV leaks and DV leak.
also try disconnecting your MAF sensor to see if the car runs better.

[GVK]

I wouldn't keep ignoring the injectors personally.

They are very common to fail.

[JTI]

Update - Still working on this problem.

I noticed my car doesn't stall when I unplug the MAF which I understand can mean a faulty MAF.

Bought a cheap new one from ebay and tried it today and saw weird results:

New MAF Plugged in - On idle the engine loops between almost stalling to just running regular rough idle. When I unplug the connector to the MAF it runs at just normal rough 

Old MAF plugged in - Car idles virtually the same (i.e. rough) whether the connector for the MAF is plugged in or not.

Not entirely sure what this means. Am going to try driving tomorrow with the new MAF plugged in to see if it calibrates after a while and improves the problem.

*Anyone here know what a healthy GTI does when the MAF connector is unplugged? Does the car stall?*

Car is going in at the end of the week for Cam follower change and DSG service, so will see if these do anything. Might see if I can get a new Divertor Valve before weekend and fit it over the bank holiday. Also may pick up some carb cleaner and look for some vacuum leaks tomorrow.

[titchy]

check for vac leak mine was like this found split vac pipe from vac pump to brake booster to crank case bugger to find but new pipe has sorted it

[JTI]

check for vac leak mine was like this found split vac pipe from vac pump to brake booster to crank case bugger to find but new pipe has sorted it

@titchy how did you find the leak?

[ROH ECHT]

*Anyone here know what a healthy GTI does when the MAF connector is unplugged? Does the car stall?*

It should run fine as it will operate from the reports of the MAP sensor alone. Typically, unplugging the MAF is one way to tell if the MAF is failed because it will usually run better while unplugged. If it doesn't run better...then it means you likely have a leak either in the turbo to and including the intake manifold, or in any of the vacuum or brake booster piping. I see you have not posted any fault/error codes...do you not have a means of reading those? A failed B1S1 O2 sensor can make a car run rough, but usually will only do so at idle. If you do not detect any leaks with the starter fluid you mentioned...try a smoke test that includes everything from the turbo to the intake manifold. But seeing its codes would be helpful to anyone trying to work this out with you.

[JTI]

^Thanks for the suggestions, I did post some codes in the original post. They do vary each time I get the fault but it's generally one or more of the following:

p0300, P0302 and P0303

Last time I did get a p0441 also. Not sure if this is a historic code however as I had this last year and I did replace the Canister Purge Valve. Might be worth scrutinising the charcoal cannister though.

I also have suspicions about the O2 sensor as I had similar issues with a previous care and I replaced the cat and an O2 sensor, which fixed it.

[Rigsby]

Mine did this the other day, flashing elm misfire cylinder 1, plug was black.
Swapped #1 coil to #4 cleaned plug and cleared codes, been fine for 3 days but waiting for it to come back

[JTI]

Mine did this the other day, flashing elm misfire cylinder 1, plug was black.
Swapped #1 coil to #4 cleaned plug and cleared codes, been fine for 3 days but waiting for it to come back

On two occasions with mine once the plugs had been either replaced, or took out cleaned and put back, it fixed the problem but only temporarily.

Sea Foamed the injectors yesterday. Was running rough during the drive to get the foam out of the system, but once I parked up and left the car for an hour it was running fine again afterwards. Also sprayed some carb cleaner around the more obvious areas in the engine to look for a vacuum leak, but nothing.

Have since changed the diverter valve also (which was massively knackered!), and car is running great at the minute. Will wait now and see how long it runs ok for.

[titchy]

How I found the vac leak I took the pipe off and sucked and blew through it  and watched for a leak there was a split where it goes into vac pump

[ROH ECHT]

^Thanks for the suggestions, I did post some codes in the original post. They do vary each time I get the fault but it's generally one or more of the following:

p0300, P0302 and P0303

Last time I did get a p0441 also. Not sure if this is a historic code however as I had this last year and I did replace the Canister Purge Valve. Might be worth scrutinising the charcoal cannister though.

I also have suspicions about the O2 sensor as I had similar issues with a previous care and I replaced the cat and an O2 sensor, which fixed it.

Yeah I saw the codes. Usually a misfire codes focused on "not all four cylinders" (P0301, P0302, P0303, and P0304...P0300 just refers to any misfiring detection.) is isolated misfiring, yes. So it would lead to plug, coil, injector, or valve damage. Or, it is leak related but is minor.

If it all returns, you may want to give the canister a visual or even pressure test. The DV fail is also a leak because pressurized intake air can instantly be forced back into the turbo inlet...as well as intake air allowed to bypass the compressor...sort of renders the turbo useless. But also surprised you found the DV failed with no code for inability to reach its boost target.?.?.

[JTI]

Update - Still having issues. Since I sea foamed my car the first time I will get the misfires but they seem to clear quicker now. Have sea foamed the car again today so will see what happens next few days. I did notice however that when sea foaming I did get some smoke from the back of the engine. Did some googling around this and couldn't find out definitively if that was normal or not???

Also did my own smoke test (with a trusty cigar!) for vacuum leaks but couldn't see anything obvious. I would expect a more constant fault if it was this though, and can't hear any whistles either.

Other symptoms I noticed is the car is a bit twitchy when I press the accelerator, especially in lower gears. I also noticed that even when running fine there is this low level murmur/bubbling noise from the exhaust when idle, like it's not quite idling right.

@ROH ECHT Yeah I was surprised I didn't get any faults for the diverter valve, but I always felt my car was a bit laggy in normal drive mode, so I guess this was why.

[TheBALDpuma]

Hi all

Similar problem here...

Rough idle when cold and a stuttery acceleration until warm. It was like this for maybe two weeks. It was booked in next week (earliest my garage could do) but today it threw it's toys out the pram. Problem there 100% of the time and running rougher than ever. Flashing eml.

Garage have checked plugs, coil and compression.  Plug two was the problem and it was filthy, but changing out doesn't fix the running. Coil and compression were fine.

Next step is a check on the injectors. I've got to wait a while until they can fit it in though. During myself out some temporary transportation as I type.

ETA... m not mechanically minded and don't know what work this entails, but would getting the cam follower and or cam chain tensioner (is that the same thing... See I really don't know) done at the same time make sense time wise? Just ticked over 100k.

[titchy]

Changing the injectors means the inlet manifold has to come off  You need special tool to refit injectors with new seals new injectors come with seals [or should] and the tool isn't needed with regard to the chain is it rattling?