Strange Behaviour-3.9 Disco

Turn the key, it starts first time. Idles at around 6-700rpm with no problems at all. Pulls away fine and then starts to lurch at about 25-30mph. It's as thoughthe fuel is being momentarily shut off and on. If i lift off it will even out again and I can cruise at 30 with no problems. A little harder on the accelerator and it happens again.

I have just replaced the throttle position sensor so I disconnected it and the same thing happens without it. The previous one had broken wires so wasn't working (see http://www.landyzone.co.uk/lz/f42/throttle-potentiometer-201249.html ) and this wasn't happening then.

Any ideas please.

If the throttle pot is new I would look at air flow meter - get multi meter on it and check the CO trim and then check the air flow signal. HTH.

Update.
I haven't had time to do anything until today. I decided to do a thorough job so I thought might as well give the Plenum a good clean, as I disconnected the TPS notice that one of the wires coming from it was broken right inside. It was just stuffed in!!
That's Britpart for you- you get what you pay for.

Would that have caused my problem?

When I get the replacement I'll check the afm.

I have posted this link at least 20 times to various people but it is truly worth it:

Rover 14CUX Hot Wire Mass Flow EFI: Service and Troubleshooting

If you haven't already read it, the info here will allow you to systematically test your whole injection system

When you say 'that's Britpart for you' the problem is they are likely to be the only people sourcing them aftermarket, nobody buys as much as them.

If its faulty out of the box though obvs you can return it, hopefully the next one will be ok

Latest update.

Finally got a working throttle pot and Hey Presto! everything was alright for a short time.
Down pipes now needs replacing, sounds like a tractor!! Did some searching for a replacement, quotes from £164 to £445. Guess which one I'm going for.

Now where did I put my wallet?

As an aside, I phoned Paddocks to return the first pot and was told they would send it back to Britpart and if they said it was no good I could get a refund after about 2 weeks. In the meantime I could order and pay for a new one, thanks a bunch.

Could b a bad fuel pump ur regulator ... check the above link for sure