Foxing Vectra X25XE V6 misfire issue
Discussion
So, my friends V6 Vectra has developed a misfire.
Easy I thought, checked the leads and they were shot, checked the plugs and they were flashing over, probably due to the leads. Changed them, no joy. Bit of t'internet searching turned up DIS or coil pack issues, changed that. Still misfiring.
Now changed the crank, cam and Lambda on the misfiring A bank and it's still misfiring.
Have read the fault codes and that lead us to the Rear Lambda sensor as it wasn't switching.
Have carried out a comp test on all cylinders and all seem ok B bank 175 +-5 PSI, A bank 190 +-5 PSI. No water in oil or oil in coolant, levels stable and have been for a long time.
So after all that work, a few quid and a bit of head scratching were foxed as to where to go next.
Symptoms are, misfire on A bank (near bulkhead) B bank is spot on. Misfire is 90% of the time, mainly under load, when unloaded, cruise idle etc it seems ok. To me it screams spark issue but have checked them and they seem ok. It did manage to burn out one of the standard plugs when we tried those so it's back on the Iridium ones. Hich I though was a tad stange, would suggest bad spark timing and hence detonation or a lean mix.
Engine has, enlarged throttle body, blended intake crossover, uprated cams and a freeflow exhaust system including cat.
To me, the next port of call was cam timing but I thought I'd see if there was any experience of this on here.
Easy I thought, checked the leads and they were shot, checked the plugs and they were flashing over, probably due to the leads. Changed them, no joy. Bit of t'internet searching turned up DIS or coil pack issues, changed that. Still misfiring.
Now changed the crank, cam and Lambda on the misfiring A bank and it's still misfiring.
Have read the fault codes and that lead us to the Rear Lambda sensor as it wasn't switching.
Have carried out a comp test on all cylinders and all seem ok B bank 175 +-5 PSI, A bank 190 +-5 PSI. No water in oil or oil in coolant, levels stable and have been for a long time.
So after all that work, a few quid and a bit of head scratching were foxed as to where to go next.
Symptoms are, misfire on A bank (near bulkhead) B bank is spot on. Misfire is 90% of the time, mainly under load, when unloaded, cruise idle etc it seems ok. To me it screams spark issue but have checked them and they seem ok. It did manage to burn out one of the standard plugs when we tried those so it's back on the Iridium ones. Hich I though was a tad stange, would suggest bad spark timing and hence detonation or a lean mix.
Engine has, enlarged throttle body, blended intake crossover, uprated cams and a freeflow exhaust system including cat.
To me, the next port of call was cam timing but I thought I'd see if there was any experience of this on here.
Yep, it's a nightmare.
As it's not my car I only get secondhand information about what happens and this is from someone who's not a engineer.
From what I can remember it just started happening. I went through the usual problems, leads were shot so changed those, put a new coil pack on etc etc and tried lots of other things but nothing has ever fixed the crap firing in Cylinder 1.
All I can think that would cause it would be a lack of dynamic compression giving an over rich condition or a spark that is only weak on cylinder 1. If that's possible.
The only other indication I've seen is that it's due to the lightened flywheel that's fitted. The crank signal isn't taken from the flywheel though so I fail to see how this could cause it.
As it's not my car I only get secondhand information about what happens and this is from someone who's not a engineer.
From what I can remember it just started happening. I went through the usual problems, leads were shot so changed those, put a new coil pack on etc etc and tried lots of other things but nothing has ever fixed the crap firing in Cylinder 1.
All I can think that would cause it would be a lack of dynamic compression giving an over rich condition or a spark that is only weak on cylinder 1. If that's possible.
The only other indication I've seen is that it's due to the lightened flywheel that's fitted. The crank signal isn't taken from the flywheel though so I fail to see how this could cause it.
I had excactly the same issue. Vauxhall garage changed cam sensors no joy, then crank sensor, still no joy. They replaced the ht leads at a massive cost. Still no joy. Took it to an indy auto electical who cleaned all the oil / gunge from the top of the rocker box that the leads were lying in, and problem went away.
ridds said:
Have carried out a comp test on all cylinders and all seem ok B bank 175 +-5 PSI, A bank 190 +-5 PSI. No water in oil or oil in coolant, levels stable and have been for a long time.
Engine has, enlarged throttle body, blended intake crossover, uprated cams and a freeflow exhaust system including cat.
To me, the next port of call was cam timing but I thought I'd see if there was any experience of this on here.
The clues are all there in your information. The difference in cranking pressure between banks is too large to be accounted for by manufacturing tolerances in any part of the engine. The chances of one entire bank wearing more than another to that extent but each cylinder on each bank being the same are negligible. The only cause can be cam timing. The cam/cams on the A bank are advanced relative to those on the B Bank by perhaps one tooth. Which bank is correct, if either, I obviously can't say for certain but 190 psi is what I'd expect a modern high comp engine to put out and 175 is low so the B bank is looking like the wrong one. They may well both be wrong.Engine has, enlarged throttle body, blended intake crossover, uprated cams and a freeflow exhaust system including cat.
To me, the next port of call was cam timing but I thought I'd see if there was any experience of this on here.
This is causing some sort of cam sensor conflict, either between banks or between the cam and crank sensors. I have no idea how this particular engine is set up but I can go by general principles. Check the cam timing, check the location of the sensor trigger on each cam. There is no guarantee with aftermarket cams that they will be ground to time in correctly without using adjustable pulleys. They could be miles out on the standard pulleys so don't go just by the standard timing marks. This is a dial gauge and degree wheel job.
Once all the lobe timings and sensor triggers are in the right places with respect to each other I think your cranking pressures will equalise and your misfire will go away.
Dave Baker
Puma Race Engines
That's what I thought oringally as well.
However, the low compression is on the wrong bank to the affected cylinder.
It's only one cylinder that is suffering and not an entire bank.
The cam belt has been changed since that first post, literally 2 weeks ago now and the misfire is still present.
However, the low compression is on the wrong bank to the affected cylinder.
It's only one cylinder that is suffering and not an entire bank.
The cam belt has been changed since that first post, literally 2 weeks ago now and the misfire is still present.
Steve_D said:
My comment about injectors remains unanswered.
Steve
Sorry Steve yeah just seen that.Steve
I did move injector 1 to cylinder 2 (first one on the opposite bank) and the problem didn't move. Checked all the connections too. They are an absolute bugger to fit on that thing. My V8 AJP rail is easier to refit!
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