Rev Blips on idle speed

Hi, apologies I couldn't find the answer to this on the forum. I tried a search but may not be using the right keywords.

I purchased my Range Rover yesterday (1996 4.0 SE Manual, LPG with 108k) and whilst driving it back home I noticed something strange with the idle speed..... When stationary in traffic the engine speed constantly jumps from almost 0 revs to 1k in a blipping motion. It gets to the point where the engine may stall then it suddenly blips and goes straight back down again and blips yet again.

The car was running on LPG so I tried running on Petrol but the same thing happened. The engine otherwise performs normally with no loss of power and doesn't seem to miss beat.

Any ideas what this may be?

Thanks.

Sounds like a problem with idle stabilisation. I don't know too much about the injection system on a '96. I might be tempted to suggest take the plenum off and give it a good clean and if there is an idle air bypass valve (stepper motor) try taking that off and giving it a clean as well.

Something is sticky or a sensor is not working properly.

Our 1999 V8 4.0 used to do that, but after we cleaned the MAF sensor plug and had a general clean up round a few other things, it stopped doing it.

It doesn't take a lot to throw the system out of kilter, and once it has all got screwy it's a real sod to get back together again.

Do one thing at a time, don't change many things at once or you'll never know what sorted the problem out.

I'd look at the inlet side first, MAF and if you have the balanced armature idle control valve solenoid then have a look and make sure that is free.

Peter

Sorry for late reply (holiday and internet issues) but thanks for advice. Since I've been driving the car, the problem seems to have sorted itself out. Hopefully will stay that way!