3.9 Running problems

I have searched but found nothing conclusive...

After fitting a new engine my Disco has developed a problem whilst running on petrol.

after a minute or so post start up it won't rev beyond ~2000rpm, it isn't a misfire or rough running, it is cutting all cylinders. the revs then drop to around 1250 rpm and she picks up again. If you were to keep the throttle depressed this would lead to a violent kangarooing.

I don't think it's coolant temp sensor - it's happening from cold and also when hot and it's a definite fuel cut on all cylinders, not rich/lean running

I don't think it's maf - see above

The only thing I can think that would cause it is a faulty TPS. my thinking is that if the TPS is signalling 'throttle shut' to the ECU when engine speed is above idle, the ecu will cut fuel assuming it's on overrun.

Has anyone else had this problem and or agree or disagree with my thoughts?

any help would be appreciated as I don't want to play component dominoes...

Cheers guys.

You can check TPS with a multi meter. Check base voltage and then check scaling. If you do a search I am fairly sure the readings have been posted somewhere in the V8 section.

You say whilst running on petrol, is this duel fuel vehicle, this certainly sounds like MAF

Yes it's dual fuel. I'll have a hunt see if I can find some data and attack the tps with my multimeter. It doesn't 'feel' like a maf problem - it's not that the fuel ratio is off - it's a very definite fuel cut at 2000 rpm that lasts until the revs drop to below 1250 at which point the fuel comes back on. Having said that, don't suppose anyone knows of a guide to check the MAF?

sidewaysste said:

don't suppose anyone knows of a guide to check the MAF?

Click to expand...

There have been a few posts in the V8 section about this -fairly simple, all you need is a multi meter (although a CO meter would be useful). You can check the AFM supply voltage, CO trim and air flow signal.