P38 4.6 Gems not revving

hi guys i got a 4.6 1996 Range Rover its converted to lpg

when i rev it slowly it can rev pretty much most of the way

when i try the same and but kick the peddle down it doesnt want to go any higher than 3k

when you try to drive it on petrol again it doesnt want to just pops like it misfiring if you push the peddle little fit it will craw

on lpg it fine it can drive and rev fully with out any issues it also does seem under powered even on lpg compare to before as it struggle to go up a hill

any ideas what could be wrong?

it could be your maf. as it dont use the maf on gas..

Could be a few things. MAF as mentioned. Petrol fuel pressure. Gas fuel pressure throwing long term trims out.

I've just had the MAF replaced on my 4.6 (no LPG). The symptoms were hesitancy when engine was stone cold, lack of power generally, and the engine wouldn't rev cleanly when accelerator was "blipped". Engine diagnostics read both banks were running lean. MAF was replaced (£150, ouch) and symptoms went away.

Trouble with the MAF is that unless it is completely broken it won't show up in the engine diagnostics. And it is a bit expensive to replace "just in case".

hi guys i have have had a brand new lucas maf on it and it doesnt change any thing still does the same any other things that could cause this

Did you get the ecu adaptions reset when you fitted the MAF ?

hi mate i did it hasnt made any differnce

anyone with a diagnostic computer near by in kent

can any one else help still not fixed

I would be checking the fuel pressure to start with. Not sure about the gems engine but the later ones run at 55 psi, best check Rave to confirm. You might want to consider blocked cats aswell.

Do these fuel trims affect the car when its on gas?

For sure.

I upset an LPG guy once by commenting that they never ever seem to change the petrol filter and then wonder why the fuel supply is low. I was wrong in his case but I think it still holds 90% true.

That said, try to work logically. You need a spark, you need fuel and you need air, right? Now work through those subsystems and you'll find it.

rewmer said:

For sure.

Click to expand...

In what way (trying to learn something here, not question your knowledge lol)

The gas ecu fires the gas injectors with the signal from the petrol ecu. So if your petrol ecu has trimmed the fuelling to give an injector pulse of 3.5 milliseconds then the gas ecu reads this adds or subtracts some time depending on how it's tuned and then fires the gas injector.

rewmer said:

The gas ecu fires the gas injectors with the signal from the petrol ecu. So if your petrol ecu has trimmed the fuelling to give an injector pulse of 3.5 milliseconds then the gas ecu reads this adds or subtracts some time depending on how it's tuned and then fires the gas injector.

Click to expand...

OK, cheers for that. Pretty sure it doesn't apply to my single point conversion but it is something to bear in mind when I replace it with a sequential front end.

Cheers.