2005 Golf periodically misfiring and knocking

2005 Golf periodically misfiring and knocking

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tweedy151

Original Poster:

4 posts

105 months

Monday 25th September 2023
quotequote all
Hi, hope I've got this in the right place. I have a small issue with my car that intrigues me, namely that it periodically misfires and/or the engine knocks a bit (sometimes quite a bit) but other times runs absolutely fine. So, my question is two fold, what do you think could be causing this and more curiously, why only occasionally? If there was an issue, why not all the time? One garage cleaned the EGR valve (made no difference after they insisted that was the issue) and the other garage don't seem to know. It is reasonably well serviced etc, new fuel and oil filters, oil changed etc. I think older engines can knock a bit as the bearings wear down or something, but it doesn't explain the misfiring. Should I put a certain kind of cleaning liquid through the engine?

edit to add, this is a diesel 2 litre engine

Edited by tweedy151 on Monday 25th September 14:40

catso

14,853 posts

274 months

Monday 25th September 2023
quotequote all
Faulty coilpack?

My Son had a 2004 Polo that had a random, intermittent misfire due to a failing coilpack.

I also had the same on my S4, though it would shut down the cylinder involved until engine stopped and restarted so quite obvious, but an older car probably doesn't?

Using VCDS I was able to see which coil and even monitor cylinder misfires during a drive, apparently (later cars) will shut down after a certain number of consecutive misfires whilst the older ones will just misfire.

In both of my cases a new coil at around £30 cured it.

the-norseman

13,411 posts

178 months

Monday 25th September 2023
quotequote all
tweedy151 said:
Hi, hope I've got this in the right place. I have a small issue with my car that intrigues me, namely that it periodically misfires and/or the engine knocks a bit (sometimes quite a bit) but other times runs absolutely fine. So, my question is two fold, what do you think could be causing this and more curiously, why only occasionally? If there was an issue, why not all the time? One garage cleaned the EGR valve (made no difference after they insisted that was the issue) and the other garage don't seem to know. It is reasonably well serviced etc, new fuel and oil filters, oil changed etc. I think older engines can knock a bit as the bearings wear down or something, but it doesn't explain the misfiring. Should I put a certain kind of cleaning liquid through the engine?
What engine?

tweedy151

Original Poster:

4 posts

105 months

Monday 25th September 2023
quotequote all
yes sorry, it's a 2 litre diesel

catso

14,853 posts

274 months

Monday 25th September 2023
quotequote all
tweedy151 said:
yes sorry, it's a 2 litre diesel
In that case, ignore my post above.

the-norseman

13,411 posts

178 months

Tuesday 26th September 2023
quotequote all
Stick some injector cleaner in the system run a few tanks of it.

thebraketester

14,708 posts

145 months

Tuesday 26th September 2023
quotequote all
Any error codes?

tweedy151

Original Poster:

4 posts

105 months

Thursday 19th October 2023
quotequote all
thanks, the injector cleaner seems to have helped.