Before I get onto my current problem it's probably worth me explaining some background.
This is not my first V8 on LPG, I had a Discovery 3.9 a few years ago, and based on that experience (i.e. it not starting after being left in a damp station car park), as soon as I got the RR I fitted NGK plugs, Magnacor leads, new Lucas coil, Dissy cap and rotor arm. All was good and as I run it on petrol and LPG I had an RPi Advance and Retard box fitted.
All was well for a couple of months, doing 75-100 miles a week.
It then started hunting badly. Initially on tick over then throughout the rev range. It would stall a few minutes after starting.
I took it to a local Land Rover specialist (as it was already booked in to get the LPG system serviced). He found a broken Lamda sensor, but could not get the time to get to the bottom of the hunting issue. Other ECUs, distributors and coils were tried, but as it was in his yard for a couple of months with the issue not getting resolved I ended up collecting it.
When I collected it I had a nightmare trip home, it stalled at every junction and the revs would die as as I took my foot off the accelerator.
Managed to get it booked into another independent Land Rover specialist, and a new Mallory Distributor and coil was fitted, timing was done, vacuum checked, plenum cleaned out etc - this has solved the hunting problem, but has given me a new issue.
If I take my foot of the accelerator it will now backfire in the exhaust. If I keep on accelerating then there's no problem, and the acceleration is better. But as soon as I take my foot off it backfires, looses power then surges back again. Does it on both petrol and LPG
This is getting frustrating. I've checked all the ECU diagnostics and I know the Lamda reading and Airflow meter readings are fine.
I'm now at the stage of working out what to do next.
The specialists have said it could be:
- sticking valves (I did a compression test and all cylinders are giving similar reading)
- stretched timing chain, may have jumped a tooth
- worn cam shaft
thanks.