Mk4 Golf misfiring in wet weather - cause?

[Twentyfour7]

Hi All

I have a Mk 4 (98) Golf Auto 1.6. I've had it since new and its done about 118,000 miles.

I have been having problems when I try and move from stationary, it appears to misfire and seems to happen when it has been raining. (it's kept outside).

After starting the car, it judders as it starts to move along for about 30 seconds and then seems to jump/ transition to a smooth first gear. It then seems to settle down and drive normally including when I pause at traffic lights and then pull away (it does not appear to misfire)

Yesterday it misfired again on starting the car . It was raining and again it juddered as I set off before transitioning through the gears as it should do . However I hit quite a large puddle of water at about 20 mph and this temporarily caused the car to feel "heavy"and judder for about 20 secs before settling to drive smoothly again.

I had a service at the beginning of the year and all the spark plugs were changed so it can't be that.

It drinks a lot of oil but I believe MK 4's do .

Water seems to a factor, does anyone have any ideas on what might be the cause please , would be helpful to narrow it down after looking at this!

https://www.repairsmith.com/i/blog/is-your-engine-...

Thanks for any thoughts/ advice


24/7

[Twentyfour7]

Hi All

I have a Mk 4 (98) Golf Auto 1.6. I've had it since new and its done about 118,000 miles.

I have been having problems when I try and move from stationary, it appears to misfire and seems to happen when it has been raining. (it's kept outside).

After starting the car, it judders as it starts to move along for about 30 seconds and then seems to jump/ transition to a smooth first gear. It then seems to settle down and drive normally including when I pause at traffic lights and then pull away (it does not appear to misfire)

Yesterday it misfired again on starting the car . It was raining and again it juddered as I set off before transitioning through the gears as it should do . However I hit quite a large puddle of water at about 20 mph and this temporarily caused the car to feel "heavy"and judder for about 20 secs before settling to drive smoothly again.

I had a service at the beginning of the year and all the spark plugs were changed so it can't be that.

It drinks a lot of oil but I believe MK 4's do .

Water seems to a factor, does anyone have any ideas on what might be the cause please , would be helpful to narrow it down after looking at this!

https://www.repairsmith.com/i/blog/is-your-engine-...

Thanks for any thoughts/ advice


24/7

[Polly Grigora]

Wait for a pitch black night, open bonnet, start engine and look for HT voltage tracking

[GreenV8S]

That sounds like a weakness in the insulation of one of the HT leads or connections.

[catso]

Is water getting onto the cylinder head?

Asking because my Son has a Renault Clio on which the driver's side scuttle vent seems prone to getting blocked with leaves etc. and when it does the rain water that doesn't drain through (when parked) runs onto the cylinder head and gets into the no. 4 spark plug/coil hole, causing a misfire.

When it happens, I need to unblock the drain and then remove the coilpacks and dry out the plug'ole and this cures it.

The engine layout in a Golf probably means this doesn't happen like the Clio but it could be getting in elsewhere?

[Belle427]

Damp in the leads?
Lift the bonnet at night and look for stray sparks, misting some water from a sprayer may help but just be careful.

[E-bmw]

Polly Grigora said:

Wait for a pitch black night, open bonnet, start engine and look for HT voltage tracking

You can help highlight HT leaks by spraying water with a hand sprayer also.

[Twentyfour7]

Thanks alot for suggestions. It is currently in garage. They ran diagnostics on it and it only alerted to possible fault on coolant sensor but when the mechanic took it for a drive and re ran diagnostics nothing came up.(by this time it had been driven for a while and was warm and driving normally)

They are going to try it again in morning ,but are keeping it undercover tonight so not sure how it will perform when they first start it .........

[hedges88]

I posted a while back on the forum that my A Class was having issues with very occasional errors for cylinder 3 misfire and also cylinder 3 rough running usually after rain or when the engine was cold. I changed just the spark plug leads because they were old and brittle and all was well for a little while and the then the problem slowly returned. I didn't apply dialectric grease to the heat shields that go over my plugs nor around the connection point for the coil packs.

Using dialectric grease resolved the issue for me. I should not have skipped doing it because it keeps moisture out. It doesn't help conduct electricity quite the opposite it insulates. My cars engine lays almost flat and the coil packs are exposed to the elements and I think it was carefully greasing the coil pack end that stopped the problem.

Don't know if this will help you any but it's a really cheap thing to try! I don't know a lot about Golf MK4 but I'm assuming you have coil packs and not a distributor

[PaulKemp]

Some Golfs had issues with the coil pack, I was rescued by the AA and he kept a Golf coil pack on the van as they failed so often.

[Scrump]

Continued over here:
https://www.pistonheads.com/gassing/topic.asp?h=0&...