3.9 stutter

Vogueseauto · Nov 3, 2006

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

eightinavee · Nov 3, 2006

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.

Vogueseauto · Nov 3, 2006

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

sam · Nov 6, 2006

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.

Vogueseauto · Nov 6, 2006

sam said:
remember to close the plug gap up a little.

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

Thanks

sam · Nov 7, 2006

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

JIM JAM · Nov 10, 2006

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.

3.9 stutter

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