1.4 Petrol with Misfire

Buchanan DTR

Buchanan DTR

Member
Scotland
A friend has a 1.4 petrol that has suffered for a while with an intermittent misfire.
It has been to a garage who have diagnosed as an "oil leak from the timing cover causing leak into cylinder 4".

Has anyone come across this issue before?
He has recently spent a bit getting it through it's MOT and is losing heart with it.
The car has done around 100K miles so not a high mileage car.
Perhaps part of the issue doing short journeys.

As ever, any opinion is welcome.

Thanks

David
 
I don’t know specifically but the FSIs often get misfires as a result of earthing problems

Presumably though he’s also mysteriously losing oil and needs regular top ups for them to reach this conclusion.
Seems a little odd because as far as my understanding goes the timing cover leaking would drip oil down the side of the engine, and shouldn’t end up in any of the cylinders…
Normally oil in the cylinders is as a result of valve stem seals leaking, or worn piston rings I think.

I’ve yet to have any top end problems myself thankfully so haven’t looked into that sort of thing, and may have missed something…

Indi
 
I had oil in cylinder 3, you can flush it out with brake cleaner, turn the engine over once you have filled with the cleaner.

Mine resulted in a cylinder head re furbish, new exhaust valves, followers and guides.
 
rotifer said:
Hi Indi,
Ends up in the well when the sealant fails.🙁
View attachment 119129
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Oops I didn’t see your reply when I sent mine…

How does it get into the cylinder from there though, shouldn’t the spark plug seal keep it out as long as it’s torqued up correctly?

Or does it just sit there and interfere with the connection between the spark plug and the coil pack?
 
Indi said:
Oops I didn’t see your reply when I sent mine…

How does it get into the cylinder from there though, shouldn’t the spark plug seal keep it out as long as it’s torqued up correctly?

Or does it just sit there and interfere with the connection between the spark plug and the coil pack?
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If the oil level, in the spark plug well reached the top of the spark plug insulator, the electrical connection to the plug would be compromised, resulting in a misfire at the very least.
Mac.
 
Buchanan DTR said:
A friend has a 1.4 petrol that has suffered for a while with an intermittent misfire.
It has been to a garage who have diagnosed as an "oil leak from the timing cover causing leak into cylinder 4".

Has anyone come across this issue before?
He has recently spent a bit getting it through it's MOT and is losing heart with it.
The car has done around 100K miles so not a high mileage car.
Perhaps part of the issue doing short journeys.

As ever, any opinion is welcome.

Thanks

David
Click to expand...
Is it an AUA or BBY? The comment on the 5th post mentioning individual coilpack would suggest BBY, but if it is an AUA our one's intermittent misfire was the 4-in-one coil pack on the end of the engine that was shorting to ground through a cracked casing and dried out insulation ; worse when engine was warmed up after around 5 minutes and in damp weather.
 
Robin_Cox said:
Is it an AUA or BBY? The comment on the 5th post mentioning individual coilpack would suggest BBY, but if it is an AUA our one's intermittent misfire was the 4-in-one coil pack on the end of the engine that was shorting to ground through a cracked casing and dried out insulation ; worse when engine was warmed up after around 5 minutes and in damp weather.
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Hi Robin, I'm not to sure so will look this evening and update. From what I have looked at on the report from the garage it suggests BBY but will confirm.
 
Sorry for the delay with a response. This does not have individual coil packs but a 4 in 1 set up. Cylinder 4 does have a small amount of oil but certainly not anything that could cause grounding. There was also a cylinder 1 misfire fault showing when I plugged in my code reader.
The HT leads look to be pretty old. Are these consumable items?
 
Buchanan DTR said:
Sorry for the delay with a response. This does not have individual coil packs but a 4 in 1 set up. Cylinder 4 does have a small amount of oil but certainly not anything that could cause grounding. There was also a cylinder 1 misfire fault showing when I plugged in my code reader.
The HT leads look to be pretty old. Are these consumable items?
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You have to consider many things, including HT leads, as "consumables" after 20 years! Look very carefully at the coil pack too, time and heat often cause hairline cracking in the case.
Compression test will rule out internal problems.
The early 1.4s, with BBY engines, are unusual in sparking two cylinders at a time, in pairs.
Mac.
 
PlasticMac said:
You have to consider many things, including HT leads, as "consumables" after 20 years! Look very carefully at the coil pack too, time and heat often cause hairline cracking in the case.
Compression test will rule out internal problems.
The early 1.4s, with BBY engines, are unusual in sparking two cylinders at a time, in pairs.
Mac.
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Just to avoid confusion the earlier 1.4i is the AUA engine (4-way single coil unit) ; the later 1.4i is the BBY (4 individual coils).

Underlining Mac's comment above, with our 1.4i (AUA) it arrived idling like a bag of spanners, misfiring gently and heavy on fuel. Replaced plugs, leads, TB, EGR, (early on), injectors, coil pack (following year), oil separator, and eventually the lambda over the next 3-4 years. 25000 miles after arrival (179000) in 6 years now running better than it was back then and about 15% more fuel-efficient. Bad idle resolved with TB/EGR ; misfires were resolved with the plugs / leads / coil pack, and fuel efficiency with injectors & finally lambda. Other things like engine lights due to mixture issues helped with new oil filler cap, coolant loss due to loose expansion tank lid and so on. All relatively simple stuff, but as the car had been given no maintenance at all for years by the look of it, all needed doing (along with brakes, suspension, a valet inside etc) - but for £350 initial purchase price there was fundamentally a good car in there needing a bit of work.
 
Thanks Robin, I do suspect it's just needing some maintenance similar to what you've mentioned. I'll start with coil and leads to rule them out.
 

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I possibly have a good set of Ht leads from my breaker if I recall they were very much dry & free from oil/dirt if required.
The car was running/performing very well prior to breaking.
 
Ami said:
I possibly have a good set of Ht leads from my breaker if I recall they were very much dry & free from oil/dirt if required.
The car was running/performing very well prior to breaking.
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Perhaps, add the coil pack if it looks in good condition.
Mac.
 
Ami said:
I possibly have a good set of Ht leads from my breaker if I recall they were very much dry & free from oil/dirt if required.
The car was running/performing very well prior to breaking.
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Thanks for the offer Ami. I have some bits n bobs to order for my TDi so for the sake of £35 for a new set I'll get them along with the controller.
The battery that was in the car was pretty low voltage so I've put a better one I had in which certainly has it starting with a bit more enthusiasm.
 
Buchanan DTR said:
Thanks Robin, I do suspect it's just needing some maintenance similar to what you've mentioned. I'll start with coil and leads to rule them out.
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Looking at that rocker cover, around the oil cap it looks as if it's had a clean - but there is wetness apparent on the ridge of the rocker cover lower down - looks to me like the oil cap isn't completely sealed?
 
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