DB7 GT, Lurching on occasion during hard acceleration
Discussion
My GT has started to Lurch the past few days.. not always but almost once each day it's used..
Driving slowly no problems seem to appear, however set off quickly and put the foot down and once the revs hit approx 4,000 or above it then lurches.. The thing is the lurch doesn't feel like a misfire... hmmm?
It tends to lurch 3 times before righting itself and then on it goes. They are VERY obvious and always feel the same, that is the same amount of lurch with the same sort of time between lurches.. they happen consecutively 1, 2, 3.
It feels to me as though someone temporarily turns the ignition off and back on 3 times.. it's that obvious.. if it were coils then it would have to be at least 6 failing at the exact same time, every time this happens, which to me seems too much of a coincidence.
So then I thought that it might be fuel starvation or faulty injectors, but again it feels like half the engine or all of it is giving up when it happens...
So it has be to be either:
1) A whole bank of coils
2) A whole bank of injectors
3) Faulty wiring
4) ECU
I've had my ELM plugged in and zero fault codes and engine light is not on.
Always starts first time,, though the lurching does tend to happen after the car has been driven a few miles (3 - 4 miles), so just about up to normal temp.
One other tidbit of info... On about 3 different occasions now I have heard what I think to be a backfire. Not big or loud but none the less a backfire... this has happened twice after the lurching.
So might point to un-burnt fuel down the pipes, which leads back to the ignition.
Are there any known problems with a common item that can cause the loss of one bank like this...?
After it's lurched I could put my foot down again and it be perfectly fine!! Quite random, but always happens in 3 bursts.
Just to add, it only seems to do this on full throttle openings.
It happens between about 4k to 6k as the car is accelerating hard.
It set's off fine.. start rolling and then hit the gas. The car picks up as it should, instant response but then as it get's up the rev range it's like it simply switches itself off and the revs drop instantly then back again then off again, then again for a third time.. always seems to be 3 times.
The result is very obvious from behind the wheel and feels liek someone is turning the ignition off and on.
Each lurch is about 1 second in duration.
At first I thought the coils. Then I though injector... but for such a dramatic change it has to be more significant, like one whole side.
The thing is it doesn't do it on demand, I can hit the rev limiter no problem for half the day then I can stop for a minute, set off again and it might do it on the first hard rev, once it's lurched it doesn't do it again for some time if at all.
Any help would be appreciated.
Driving slowly no problems seem to appear, however set off quickly and put the foot down and once the revs hit approx 4,000 or above it then lurches.. The thing is the lurch doesn't feel like a misfire... hmmm?
It tends to lurch 3 times before righting itself and then on it goes. They are VERY obvious and always feel the same, that is the same amount of lurch with the same sort of time between lurches.. they happen consecutively 1, 2, 3.
It feels to me as though someone temporarily turns the ignition off and back on 3 times.. it's that obvious.. if it were coils then it would have to be at least 6 failing at the exact same time, every time this happens, which to me seems too much of a coincidence.
So then I thought that it might be fuel starvation or faulty injectors, but again it feels like half the engine or all of it is giving up when it happens...
So it has be to be either:
1) A whole bank of coils
2) A whole bank of injectors
3) Faulty wiring
4) ECU
I've had my ELM plugged in and zero fault codes and engine light is not on.
Always starts first time,, though the lurching does tend to happen after the car has been driven a few miles (3 - 4 miles), so just about up to normal temp.
One other tidbit of info... On about 3 different occasions now I have heard what I think to be a backfire. Not big or loud but none the less a backfire... this has happened twice after the lurching.
So might point to un-burnt fuel down the pipes, which leads back to the ignition.
Are there any known problems with a common item that can cause the loss of one bank like this...?
After it's lurched I could put my foot down again and it be perfectly fine!! Quite random, but always happens in 3 bursts.
Just to add, it only seems to do this on full throttle openings.
It happens between about 4k to 6k as the car is accelerating hard.
It set's off fine.. start rolling and then hit the gas. The car picks up as it should, instant response but then as it get's up the rev range it's like it simply switches itself off and the revs drop instantly then back again then off again, then again for a third time.. always seems to be 3 times.
The result is very obvious from behind the wheel and feels liek someone is turning the ignition off and on.
Each lurch is about 1 second in duration.
At first I thought the coils. Then I though injector... but for such a dramatic change it has to be more significant, like one whole side.
The thing is it doesn't do it on demand, I can hit the rev limiter no problem for half the day then I can stop for a minute, set off again and it might do it on the first hard rev, once it's lurched it doesn't do it again for some time if at all.
Any help would be appreciated.
Yes, I was going to do this as a matter of course.. especially the idle valves..
The thing is it only ever seems to do this once per day, and from the pattern that is emerging always after the car has been driven, warmed up and then stopped, for example nip into a shop.
Come out, start car drive away put foot down, then it lurches usually when in 1st or 2nd gear but after that it's fine.
Could be the throttle bodies and/or Idle valves, but if they were bunged up enough to cause a problem I imagine it would be happening much more frequently.
Still it's a job on my to do list and will get done as part of routine maintenance.
In fact I'll start a tick box list for jobs specific to this problem. :-)
Thanks for your input.
The thing is it only ever seems to do this once per day, and from the pattern that is emerging always after the car has been driven, warmed up and then stopped, for example nip into a shop.
Come out, start car drive away put foot down, then it lurches usually when in 1st or 2nd gear but after that it's fine.
Could be the throttle bodies and/or Idle valves, but if they were bunged up enough to cause a problem I imagine it would be happening much more frequently.
Still it's a job on my to do list and will get done as part of routine maintenance.
In fact I'll start a tick box list for jobs specific to this problem. :-)
Thanks for your input.
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