View Full Version : engine missfiring when hot
Hi there guys,
Hope you can help me on this one. Have a uk TT running bpu.
I seem to be missfiring and running lumpy only after i take the car out for a run and then switch it off and start it up again???
So when i start it up from a cold start its fine. I hit 1.3 bar fine.
but only when i swtich it off i.e at a petrol pump and then start it up again it runs lumpy like its missfiring and running on 5 cylinders :rolleyes:
If i let it cool down for long enough it starts up fine and runs normal. Weird dohhh
Ive changed my spark plugs yesterday and took it out for a run and it done the same thing so it wasnt the plugs. Any ideas?
thanks in advance. :)
i had this when my FCD was faulty.
Exact same problem.
revs at idle going up and down too?
Just out of interest what plugs did you replace them with ??
I am guessing that he is using stock heat rated plugs.
Just a guess, I am hoping that I am wrong though Ray. :)
I am guessing that he is using stock heat rated plugs.
Just a guess, I am hoping that I am wrong though Ray. :)
Reason I ask is because I had the same symptons when my plugs where shot a change to a new quality set sorted it. The plugs I had in where high rated just a little worse for wear.
I know someone who had a service and there car was the same but had cheap plugs in again a change to uprated ones sorted it
Just out of interest what plugs did you replace them with ??
Hey guys thanks for the replies. I replaced my plugs with the NGK BCPR7ES i left the gap at 0.7mm
Prior to that i had Denso IK24's.
Was thinking of doing the coil pack clips... Could it be those? :rolleyes: I looked at mine yesterday.. they dont look to bad thou.
I would imagine a coil pack breaking down or even bad connection would be more prominent when actually driving the car though. As the problem seems to be Hot starting related, it could be a faulty fuel pressure up VSV??
markssupra
04-02-07, 12:57
I had a very similar problem which turned out to be a small split in the fuel pipe inside the tank. 20p piece of pipe - sorted. Never had the problem again. Might be worth checking before throwing loads of money at it trying to cure it.
ahhh some good ideas gents... I want to try and diagnose this myself. Taking it somewhere will cost me millions!
As for the faulty fuel pressure up VSV, any ideas on how to test it? Continuity?
The fuel pipe seems like a weird one, how the hell did you diagnose that one Mark? How comes it was only when the engine was hot that u was missfiring? Weirdddddddd but il have to check it to elimiinate it. :)
thanks for ur help.
markssupra
04-02-07, 14:12
No idea why it only run like sh*t when hot. But it would run fine starting from cold but as it got hotter it ran worse.
One garage I asked said it could be a sticking injector, but I thought I would check what I could before spending loads of money.
I diagnosed it as fuelling because another car I had had a similar problem and that turned out to be a blocked inline fuel filter. As I had already changed the fuel filter on the supe I assumed it was'nt that and then just checked the pump and small filter on that. Lucky enough that was the problem, I was thinking about taking it for diagnostics but where the hell do they stop checking and changing parts only to find it is something stupid and then charge you an arm & a leg.
have you checked the induction?
on my wifes 1.8 v6 mx3 when it was hot the cracks in the induction pipe had widened and was letting in too much air and the sensor didnt like it.....just a thought
What was the condition of the plugs that you removed ?
What was the condition of the plugs that you removed ?
The plugs look a lil black... Does that mean im overfuelling? :rolleyes:
Didnt change them for a while since i heard they need to be changed every 30k miles. Here is a pic... What do you think?
i had this when my FCD was faulty.
Exact same problem.
revs at idle going up and down too?
...
I might be wrong, but I'm sure you need t change them around every 10k, or more for BPU/Small Single? I'm sure I saw a thread about this a while back. I'll take a search,. :)
I might be wrong, but I'm sure you need t change them around every 10k, or more for BPU/Small Single? I'm sure I saw a thread about this a while back. I'll take a search,. :)
Yep i agree you are right :) I know that now :blush:
i had this when my FCD was faulty.
Exact same problem.
revs at idle going up and down too?
Hey mmm nawps revs dont go up and down as such... Just car seems lumpy, sounds like a Subaru :( horrid ohhh and the exhaust wobbles alot lol:innocent:
dr_blackman
05-02-07, 20:47
My n/a does that occasionally, usually when its between temperatures like its not sure what its doing.... i.e. driving it a few miles parking up then half hour later getting in it and it seems to be lumpy and revs go down alittle to about 500-600... i thought it may be me changing from super unleaded to normal but its done it since i've stuck to super :( Weird!
the plugs do seem on the rich side of the air/fuel mixture, have you checked the wires to your coolant sensor ? other causes of fouled plugs could be wrong heat range on plugs and possible bad connections.
I would suggest booking your car in for a full engine rebuild and single conversion. Should sort it ;) (hope you get it sorted, wish i could help)
I would suggest booking your car in for a full engine rebuild and single conversion. Should sort it ;) (hope you get it sorted, wish i could help)
Do you work for TDI :D
Is the car throwing any fault codes? or are there any stored.
If you have changed plugs, and the car drives fine when cold, and only shows trouble when hot, it could also be either a cam position sensor or crank position sensor breaking up under heat, or maybe the Igniter breaking up under heat.
Do you work for TDI :D
:rlol:
Big thanks to Matt Harwood... :)
Who traced fault to rare but faulty RLTC unit.
Excelent, well done matt!
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