p38 backfiring

Hi all, I really hope someone can help as I'm at my wits end. I went laning a few weeks ago and half way through the day my 1996 p38 4.6, started sounding rough, lacking power and backfiring. I later found out the exhaust manifold was cracked and it was replaced. However, the problem persisted. My local landy specialist hooked it up to autologic which pointed out a duff o2 sensor which was replaced to no avail. I have also been advised to do plugs and leads which has not helped. Today I went back to the garage and they did adaptive reset. This has completely naffed everything up and the car is much worse. It is now backfiring constantly (1800 rpm under load before), heavy smoke, no power at all and it sounds terrible. I have also unplugged maf which made no difference. It is the same on both lpg and petrol. Any help appreciated. Thanks. Jon

put petrol over it and strike a match

Find a LR indy that can use its kit properly.Gems is a very nice system to diagnose/work with - to anyone who can be bothered to understand it.

Thanks for that. Any idea of anyone who may be able to help? I loved the car when it was right and I don't want to get rid but mot due and I need a car. The lr indy I took it to said there were no faults logged

try the crank sensor,i bought a 4.0 se that wouldnt start was just backfiring.turned out the crank sensor was slightly rubbing the flywheel and not telling it to spark at the correct time a couple of small washers between sensor and mounting point and all was fine .no faults were stored and auto electrician couldnt find fault either,you will see rub marks on sensor if this is the problem.might be worth replacing it if it has marks

Cheers mate. I will have a look and hopefully report all is well

I've had crank sensor off. There isn't a spacer on it at all. Where did you put your spacer? Thanks jon

If the manifold cracked out laning, did the exhaust get a whack? Maybe something got crushed and you have partial blockage.

That thought did occur to me. However its running like a bag of spanners and its passed its mot today with flying colours. If the cat was blocked or collapsed I would have thought it would be reflected on emissions? Ill have a gander anyways. Thanks

did the end of your crank sensor have score marks?if it doesnt then it shouldnt be rubbing the flex plate.i had to put a couple small washers in between the sensor and mounting on the bell housing,might still be dodgy sensor though.

No marks on it at all. I've spaced it anyway just to try it and there's no difference. Oyher possibilities coul be coil pack? Inlet manifold? Any thoughts? Thanks very much to all who have replied

Apologies, Disco, for crashing your thread.

eightinavee said:

Find a LR indy that can use its kit properly.Gems is a very nice system to diagnose/work with - to anyone who can be bothered to understand it.

Click to expand...

May I invite you then to comment on my thread http://www.landyzone.co.uk/lz/f10/gems-ecu-155030.html? Judging from the flurry of ideas I think I finally managed to have everyone stumped.

Does anyone in south\west yorkshire have any diagnostic kit and would be prepared to have a look at my rangie pls? I'm struggling to find someone who knows what they're on about. Cheers

I would say by the sounds of it coil Pack. Is it worse when you put your foot down and put the engine under load??

Much worse mate. On a flat road once its moving it not too bad. Setting off or show it a hill, and it drives like a moped.

More likely a low reading maf,this narrows down the injector pulse width and makes the engine very lean.