3.9 stutter

My 1992 LPG'd 3.9 has started to stutter whilst running on gas. It happens under heavy acceleration and seems to stutter through a certain rev range until it clears at the top and takes off nicely.
It doesn't happen on petrol, just on the gas.

Does anyone have any suggestions?

Thanks

STU

Yes, sort it out before you need a new engine.Take it to an LPG specialist who will repair it and set it up using an oscilliscope to watch the oxygen sensors working - ensuring a correct Gas/Air mixture.Carry on as it is and the Head gaskets will blow or you will head towards a porus block.

My car doesn't catalytic convertors so therefore doesn't have lambda or oxygen probes.
I must agree with you though, I really am considering taking it to an LPG installer/service agent next week to have it looked it.

One thing I have noticed today is that the stutter is not constant, one minute it's there and the next it's not. Someone has suggested a change of plugs.

It's baffled me, this one.

Thanks

had the same thing on mine. though mine was hard to start as well. new coil, plug leads and a set of plugs later everything is fine. remember to close the plug gap up a little.

sam said:

remember to close the plug gap up a little.

Click to expand...

Don't suppose you know what the plug gap should be? I understand it that they are different to straight petrol engines.

Thanks

I have set mine to 0.6mm they seem to be OK at that

I had the same problem with mine recently, fine on petrol,intermittent running/backfires on gas! The ignition system has to be in top condition for the lpg to work properly.After checking everything I changed the distibutor cap and it solved the problem.