OK so an update on this. Unfortunately Friday did not go so well - here is what happened
Firstly we tried all of the following
1) Ran engine with the plenum blocked at the point the main vac pipe connects.
2) Replaced inlet manifold and injector rail with known good item
3) Also replaced DBW throttle bodies with a proven item
4) Whilst inlet removed, all seals, seating etc checked to ensure there was no major air leaks - all was fitted correctly
5) Cam timing was checked - the timing was spot on, and all cams were fitted in the correct keyways
6) 1-3-5 coil pack swapped out - no difference
7) Crank sensor replaced with brand new item
8 ) Known good original cam sensor fitted
9) known good replacement engine ECU fitted
10) new spark plugs fitted to 1-3-5
11) Compression test on 1-3-5. Compression was unusually high, much more so than before. Reading 220psi on all cyls. Although this test was with a cold engine - so may be normal?
The engine was tried after all of the above, and each time the result was exactly the same. running absolutely perfectly at 2,000 rpm or above, (easily on all six) but when idling - misfiring / idling roughly, with 1-3-5 misfire codes getting logged.
I tried a little experiment with the lambda sensors which I think was interesting. Firstly I unplugged them all, cleared the codes to reset, and idled the engine. It was idling for ages, and DID NOT log a misfire code with the lambdas unplugged. It was still running rough though, not idling great with an intermittent misfire type feel.
after that, I plugged in JUST Bank 1, Sensor 1, and ran the engine. Likewise, the misfire codes did not materialise.
I then plugged in JUST bank 2, sensor 1, and ran it again. It then gave me the misfire codes for 1-3-5 bank, as it was doing before.
So. WHY when the lambda for the bank reported the misfire is plugged in, it doesn't throw the codes, but the lambda for the other bank is plugged in, it does? That makes no sense at all
Also - at idle, the lambda on bank 1, is cycling normally, between 20-700mv, but the lambda on bank 2 is sat still at around 20mv, and does not start cycling until you hold it at higher revs. This should surely be the other way around, if bank 1 is the problem bank?
At this point we recalled the camshafts had come out of the 1-3-5 bank during the 2-4-6 head removal, to allow us to clean the engine and inspect the 2-4-6 bores. I handed the cams to steve to mark as Inlet and Exhaust during this process, but we thought we'd better check the correct ones had been fitted - so the cam cover came off. Low and behold, stupidly, we had got the 1-3-5 cams the wrong way round. (I'm really annoyed at myself but that's another story). Basically the G cam was on the inlet, and the J cam was on the exhaust side, whereas it should be vice-versa.
I began to think this could be the only explanation - thinking perhaps with the valve durations being different due to the wrong cam profiles, the engine wasn't breathing properly on bank 1. So we stripped the thing down again and changed the camshafts over to the correct positions.
I honestly thought we'd be onto a winner having found something wrong.
Turned the key in excitement afterwards thinking we'd cracked it - but no such luck. It started, but almost refused to idle at all. Gave it some revs, and as it's revved, it is giving an intermittent POP (a very loud one!) noise which appears to be coming from the inlet system. It immediately logs misfire codes for 1-3-5 again.
The engine was allowed to idle at this point, and died. It refused to start again, and was showing classic flooding signs. With throttle at WOT and cranking, it would try to start but wouldn't catch. I removed fuse 18 to stop it getting fuel, and cranked at WOT - it appeared to run, roughly, for a few seconds on whatever fuel was left in the system. I put fuse 18 back in, and it then started (only at WOT) but wouldn't idle for more than a few seconds.
Again, timing spot on, double checked by us both. Inlet system came out AGAIN to check for air leaks etc - nothing at all.
I have to admit, I'm struggling for ideas here!! As EVERYTHING else has been checked or swapped out, aside of the 1-3-5 head (which has good compression so should be OK, and was fine before) - I don't actually know what else to try or check?
Any ideas, on this very very strange problem, would be appreciated. We are toying with the idea of having this car recovered to me, to work on at leisure at home, as I've racked up 600 miles and 36 hours work, and still haven't managed to fix this one!!
I am not properly charging for this work, as per my original promise, but it's still costing steve a little in fuel, and I'd like to keep this cost down if possible, so want to fix it once and for all in the next visit
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Topic: Engine Loom (Read 42588 times)