P38 misfire

Just when things seemed fine (never say that with a P38) mine has developed a symptom. In short I have plugged in a diagnostic (Launch X431) and it shows up Misfire cylinder 7 and Multiple engine misfire. Strangely enough it also shows Misfire when fuel low/ empty (which it isn't at the moment). Changing plugs/ leads doesn't cure it so I am now considering the coil pack. Usual symptoms of not so smooth running and lack of power on acceleration. Disconnecting plug leads in turn confirms nothing going to No.7 (back left). Any advice appreciated particularly how to get to the coil/ distributor down the back of the V and how it is attached. It's a 2000 4.0 non lpg.

befor you start spending on it test the maf senser, get it hot get some body to sit in keeping it running and take senser out, give it a few mins if miss goes you have found your prob..

Did that the other night before running the Launch, it ran ok but didn't get rid of the prob as it is still there.

If you have live data on your launch, you can check the MAF to see what it is flowing or reporting at least. Check the injection timings - expect about 3 - 3.5 ms at idle. Check to see if the O2 sensors are switching between .0v and .8v on your engine. Get the fuel pressure checked aswell. Not sure about the 4ltr, but the 4.6 is about 55psi- - 3.5 bar. Check for air leaks around the inlet manifold using carb cleaner - spray it around the joints and if the idle picks up - bingo.

rewmer said:

Check for air leaks around the inlet manifold using carb cleaner - spray it around the joints and if the idle picks up - bingo.

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thats a good tip, never thort of that before!!!:doh:

i'm gonna go off and use that tip and recomend it to the rrc owner having probs.

And do you know what Gav? I aint even going charge for that.

Everything looked normal and within range so coil pack now methinks. Just as well I've not had it long so it's going back to the dealer (not main) on Tues. (I'll have to put up with a Daewoo trade courtesy car for a few days though!!!!!!!!!)

New coil pack fitted - just as well it's still under warranty. Still had to clear the stored fault codes myself though! Ran through the live datastream and showing all ok.