Hi All, hoping to beg a little insight here, particularly if somebody else has come up against this problem...
Got a 3 series E46 in at the moment. Its a 318ti with a N42B20A engine, 2001 but pre EOBD with 86 000 miles.
It arrived as a non runner. Having diagnosed that the timing chain had become slack and jumped some teeth on the ex side, I have replaced the timing gear (ie. guide rails, tensioner - new design of tensioner fitted).
The car now runs well, except for a hesitance off idle that has all the characteristics of a missfire...
Upon getting it started for the first time, this hesitance was immediately apparent. With codes
27DA - Alternator fault
P274E - Unknown (at the moment)
2744 - Missfire Detection cyl 4
The intruiging thing is that this 'missfire' clears completely after 2000rpm, irrespective of load. But still I had to start somewhere, so swapped plug from cyl 1 to cylinder 4, and swapped coil stick from cyl 2 to cyl 4. Cleared faults and tried again, code was set again.
Next I got the scope out and looked at secondary's on cylinder 4 v's cylinder 2, was happy with what I saw.
Next I looked at injectors, 1 v's 4 and again I'm happy with what I saw (electrically atleast). Decided to swap injector 1 for injector 4 and see if the faulty cylinder was now cylinder 1.
I started the car up and was amazed but baffled to find the fault gone, so quickly went out for a test drive and was very happy with the car. Came back turned it off and upon restarting 5 mins later the fault is back. However the code will not set now, the hesitance remains but I simply cannot get the code set.
Had a word with the owner and explained the situation, he informed me the missfire had developed some 10 months before the timing issues and that prior to the timing rebuild it had been much worse than it is now.
Next plan is a fuel pressure test, fuel pump current test and a snap throttle looking at MAF, lambda, and fuel pressure.
Switch rate of lambda is slow, (managed to view live data with texa tool), but I want to be a bit more sure of the fault before I spend someone elses money on parts.
Sorry for the rambling explanation, but any advice welcomed.