E46 M3 backfire
Discussion
As the title suggests I get a small pop every time I change gear on a cold engine, it stops after about 600 yards when the engine warms up, any one else's does this? the oil, filters and plugs are new, the plugs were a perfect straw colour and nice and dry when I changed them, so assume engine is in good nick, My mechanic suggests it could be head gasket as they can go in between the pistons on these cars so you don't get the tail tail signs of this problem, the lambda sensor flagged up with a fault but he says it wont be that but something causing it to flag up, he reset the fault codes and nothing has flagged up since so it seems electrically nothing wrong. I did google it and I seemed to find lots of people saying theirs does the same but no explanation as to why. the car is a bit lumpy and grumpy when cold but been told this is normal for these, so can any one shed any light on this please??
Sounds quite normal to me. E46 M3 are renowned for being a little rough on start - particularly with cold ambient outside air temperatures.
The phenomena is often made worse if they have an aftermarket exhaust system fitted. Also, selecting 'Sport' mode straight away accentuates it and makes the car a little jerky at low speeds (particularly SMG cars) until it has warmed a tad.
The phenomena is often made worse if they have an aftermarket exhaust system fitted. Also, selecting 'Sport' mode straight away accentuates it and makes the car a little jerky at low speeds (particularly SMG cars) until it has warmed a tad.
Im still curious as to what causes it though if that was an old fashioned car you'd probably blame the air and fuel mixture and have it tuned up, but cars seem so sort that out themselves these days. I do get a bit of pinking at low revs too when the engine is warm, is that common too?
I would be careful just writing this off as common. My M3 does not do this. It is a little snappy when cold but its a big engine to warm up. It does not backfire or sound over fueled though.
Don't forget that people mostly only write their problems on the forums, making them appear common. There are thousands of other owners out there that don't take to the forums as their cars are running fine!
I would get another independent opinion from another independent specialist.
Don't forget that people mostly only write their problems on the forums, making them appear common. There are thousands of other owners out there that don't take to the forums as their cars are running fine!
I would get another independent opinion from another independent specialist.
Andy70 said:
Upset with my technician more than anything then as it sems quite common and he seemed baffled by it 17 years BMW experience too, you'd think he'd know better, he was trying to lure me in for a compression test too lol
They are well known for being a bit rough when first started from cold but I absolutely wouldn't describe it as a backfire or a pop. On mine it just feels like power delivery is stumbling slightly with a slight but noticeable low frequency surge. I just put it down to the fact that the engine is in a fairly high state of tune and the initial warm up sequence is probably a bit of a juggling act.
Trtj said:
I would be careful just writing this off as common. My M3 does not do this. It is a little snappy when cold but its a big engine to warm up. It does not backfire or sound over fueled though.
Don't forget that people mostly only write their problems on the forums, making them appear common. There are thousands of other owners out there that don't take to the forums as their cars are running fine!
I would get another independent opinion from another independent specialist.
sorry didn't mean to offend, but for a car to have a common fault, doesn't indicate they all do it, I mean my Impreza's I owned had 'common' faults and they are amongst the most reliable cars around, for example clutch judder was common, but I expect most didn't have that problem Don't forget that people mostly only write their problems on the forums, making them appear common. There are thousands of other owners out there that don't take to the forums as their cars are running fine!
I would get another independent opinion from another independent specialist.
You mentioned that in your OP Andy.
To recap,'being a bit lumpy and bumpy' when cold is considered normal for these cars. Ive had mine for years and it has always done it, but I'd be slightly concerned about a pop or backfire when changing gear. Head gasket failure usually causes a bit of pinking but I do think a compression test is worth doing.
To recap,'being a bit lumpy and bumpy' when cold is considered normal for these cars. Ive had mine for years and it has always done it, but I'd be slightly concerned about a pop or backfire when changing gear. Head gasket failure usually causes a bit of pinking but I do think a compression test is worth doing.
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