Funny 'misfire' - thoughts?
Discussion
Hello chaps,
Got a funny 'misfire' problem that's starting to annoy me now...
When you swiftly press the accelerator the rev's pick up and then the engine does an almighty 'stutter' and then carries on as normal. If you press the throttle more slowly it behaves perfectly normally with no 'stutter' and carries on to the red-line.
When on Mike's rollers we thought it might be the waste gate sticking on the front turbo, this has been stripped, re-built and it working normally, yet the problem persists.
I've done the fuel pump mod, again, made no difference. Next on my list is to replace the hose from the tank to the pump as from reading other posts this could be the culprit.
But, before I do drain the tank etc, are there any other thoughts?
Got a funny 'misfire' problem that's starting to annoy me now...
When you swiftly press the accelerator the rev's pick up and then the engine does an almighty 'stutter' and then carries on as normal. If you press the throttle more slowly it behaves perfectly normally with no 'stutter' and carries on to the red-line.
When on Mike's rollers we thought it might be the waste gate sticking on the front turbo, this has been stripped, re-built and it working normally, yet the problem persists.
I've done the fuel pump mod, again, made no difference. Next on my list is to replace the hose from the tank to the pump as from reading other posts this could be the culprit.
But, before I do drain the tank etc, are there any other thoughts?
GTO400 said:
Sounds like over-boost and the Ecu cutting the ignition, probably caused by the cold ambient. Look at your boost gauge to check.
There is no overboost cut. Have you checked the spark plug gaps, what boost are you running ?
If gaps are ok then coipacks could be the problem, borrow a good one and try it in all six positions !
Hmmm, plug gaps could well make sense - the sudden extra boost could be blowing them out.
Thanks for your offer Simon, I'll take a look and re-gap the existing, if no better then I'll take you up on it.
Edited to add, what plugs should it be running?
Thanks for your offer Simon, I'll take a look and re-gap the existing, if no better then I'll take you up on it.
Edited to add, what plugs should it be running?
Edited by Duke Thrust on Monday 8th March 15:54
Duke Thrust said:
I've done the fuel pump mod, again, made no difference. Next on my list is to replace the hose from the tank to the pump as from reading other posts this could be the culprit.
But, before I do drain the tank etc, are there any other thoughts?
If it's the fuel hose from tank to pump you will find that it only causes problems when the engine bay is heat soaked (and the hose gets a bit 'floppy'). If your engine stuttering problem occurs when the engine bay is cold then it's more likely to be plugs/gaps etc etc. But, before I do drain the tank etc, are there any other thoughts?
Yep, it was no wonder they were getting blown out, they were set to 60 thou - eeeek!
I've got a new set of plugs on order so will fit them, that way I'm 100% certain it's got the right plugs at the right gap.
It's a bit irritating really as ages ago I did (very) briefly wonder about the plugs and remembered that the dealer that I bought the car from had given it a full service. Naturally I'd assumed they'd check something like what to gap the plugs to, they specialised in Italian exotica so I'd hope they weren't complete numptys.
Still, my own fault for not checking earlier, feel very sheepish.
Edited to add:
I undid the 8 bolts that fix the plenum in place and gently propped it up to gain access to the rear 3 spark plugs. Nothing needed to be unplugged from the plenum, enough room without anything being under tension. Is there a recommended way or is this the norm?
I've got a new set of plugs on order so will fit them, that way I'm 100% certain it's got the right plugs at the right gap.
It's a bit irritating really as ages ago I did (very) briefly wonder about the plugs and remembered that the dealer that I bought the car from had given it a full service. Naturally I'd assumed they'd check something like what to gap the plugs to, they specialised in Italian exotica so I'd hope they weren't complete numptys.
Still, my own fault for not checking earlier, feel very sheepish.
Edited to add:
I undid the 8 bolts that fix the plenum in place and gently propped it up to gain access to the rear 3 spark plugs. Nothing needed to be unplugged from the plenum, enough room without anything being under tension. Is there a recommended way or is this the norm?
Edited by Duke Thrust on Thursday 11th March 09:36
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