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Author Topic: Misfires and rough idle.  (Read 719 times)

Offline Skapligt

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Misfires and rough idle.
« on: October 14, 2024, 01:36:53 pm »
Hello!

I thought I should try this forum since nothing else helps and Im out of ideas.
Sorry for questionable english but Im from Sweden.

SOOOO

I bought a Golf GTI 2 weeks ago, knowing it ran very bad.

Started cleaning plugs which helped but still lots of misfires.

Changed plugs, no improvement
Changed 2 injectors which were bad. The other 2 works fine
Changed coils, no improvement
Changed PCV, no improvement
Cleaned valves from carbon, no improvement

Some things I have noticed.
If I take out oil stick with engine idle it goes rough and when I put it back in it runs good for a while. Then rough again. Same with oil cap for filling.
Pretty much water/oil? in exhaust. Puddle behind car after some idleing.

I have VCDS and have checked alot with it. But not really sure what is good and what is problematic.

Compression test was good.

What is the next step for me?

I have searched alot of forums and tried it all but nothing seems to help.

Thanks in advance.

Offline PorkPieBandit

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Re: Misfires and rough idle.
« Reply #1 on: October 15, 2024, 12:55:47 pm »
Have you tried unplugging the MAF and seeing how it runs? If it runs better unplugged could be that needs replacing.

Offline mjmallia

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Re: Misfires and rough idle.
« Reply #2 on: October 15, 2024, 01:58:01 pm »
When was the cam belt done? timing chain done? Cam adjuster oil pressure rings checked?
Mike

South Coast

S3 8L ---- Golf Mk4 GT TDI ---- Lupo GTI ----  A4 B6 Sline ---- Golf Mk5 GTI

Offline Skapligt

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Re: Misfires and rough idle.
« Reply #3 on: October 15, 2024, 06:58:26 pm »
Have you tried unplugging the MAF and seeing how it runs? If it runs better unplugged could be that needs replacing.

Yeah tried that also. No difference :(


When was the cam belt done? timing chain done? Cam adjuster oil pressure rings checked?

I will check the rings. But would that just affect idle? It only misfires on idle now. And now most on cylinder 4. A couple of days ago it was cylinder 3 that was worst.

Offline mjmallia

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Re: Misfires and rough idle.
« Reply #4 on: October 16, 2024, 08:52:38 am »
Yes, it would make it sound lumpy and the chain would most prob rattle
Mike

South Coast

S3 8L ---- Golf Mk4 GT TDI ---- Lupo GTI ----  A4 B6 Sline ---- Golf Mk5 GTI

Offline mjmallia

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Re: Misfires and rough idle.
« Reply #5 on: October 16, 2024, 08:53:45 am »
Have you carbon cleaned the intake valves....they clog up and create misfires like I had once......lots of info on that one.
Mike

South Coast

S3 8L ---- Golf Mk4 GT TDI ---- Lupo GTI ----  A4 B6 Sline ---- Golf Mk5 GTI

Offline Skapligt

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Re: Misfires and rough idle.
« Reply #6 on: October 16, 2024, 07:01:35 pm »
Yes, it would make it sound lumpy and the chain would most prob rattle

No rattle at all. No problems driving. Just problems at idle.

Have you carbon cleaned the intake valves....they clog up and create misfires like I had once......lots of info on that one.

Yes I have cleaned it. It was not too bad with carbon.

Im out of ideas soon :(


Offline mjmallia

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Re: Misfires and rough idle.
« Reply #7 on: October 16, 2024, 09:26:42 pm »
A boost leak will also give a very lumpy idle.

Smoke test it and check the hoses. I had a leak from the oil filler neck extension that gave me a lumpy idle.

 The bond had gone so had to remove it and mount the oil cap direct to the cam cover.......an easy check

Also the hoses off the PCV become very brittle and crack.....those were leaking for me also, soon after a carbon clean due to their removal.
Mike

South Coast

S3 8L ---- Golf Mk4 GT TDI ---- Lupo GTI ----  A4 B6 Sline ---- Golf Mk5 GTI

Offline Skapligt

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Re: Misfires and rough idle.
« Reply #8 on: October 16, 2024, 11:33:28 pm »
A boost leak will also give a very lumpy idle.

Smoke test it and check the hoses. I had a leak from the oil filler neck extension that gave me a lumpy idle.

 The bond had gone so had to remove it and mount the oil cap direct to the cam cover.......an easy check

Also the hoses off the PCV become very brittle and crack.....those were leaking for me also, soon after a carbon clean due to their removal.

I´ll have to do a smoke test. Any tips for that. How to do it properly?
I´ve sprayed all over the engine to look for leaks but nothing.

Did this give you misfires or just a rough idle?

PCV hoses are new.

Offline mjmallia

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Re: Misfires and rough idle.
« Reply #9 on: October 17, 2024, 05:50:16 am »
A very lumpy idle.

Are you sure they are misfires, as in you are counting them on VCDS
Mike

South Coast

S3 8L ---- Golf Mk4 GT TDI ---- Lupo GTI ----  A4 B6 Sline ---- Golf Mk5 GTI

Offline Skapligt

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Re: Misfires and rough idle.
« Reply #10 on: October 17, 2024, 10:03:35 am »
A very lumpy idle.

Are you sure they are misfires, as in you are counting them on VCDS

Yepp I see them in VCDS.