persistent recurring fault on '89 740 GLE auto (B230E engine)

Can anyone please help? I bought my 740 GLE auto estate about 4 months ago, from a man who was going to scrap it because of a running fault. He'd taken it to a Volvo garage and been told that the fuel distributor was faulty, and it would cost in the region of £850 to rectify the car. Even though he's had the car from new, and the bodywork is immaculate, this was more than the car was worth.
I fitted a second hand fuel distributor/air flow unit and it ran perfectly for about two months. It then started to go wrong, developing the same fault it had previously. The faults are:

1) It sounds like it's only firing on 2 cylinders when it starts up (starts first time though). When it warms up it fires on all 4, but sounds rough
2) It won't rev above 3000 rpm
3) It only gets up to about 25-30 mph on the flat, but if you put your foot on the throttle it dies off. It kicks down the gears, but the revs die right off. When the throttle is released it goes back up the gears, and the speed picks up slightly to about 25-30 mph.
4) When it comes to a hill it doesn't want to play at all. The engine drops off to about 1000 rpm, and if the hill isn't too steep it'll crawl up it. If it's a steep hill it just comes to a dead stop
4) If you floor the throttle it drops down the gears, but goes even slower
When it's warm it ticks over okay, but revs very roughly, and still wont go above 3000 rpm

I fitted another distributor/airflow unit, and new injectors and seals. The car has run perfectly for a couple of months, but has now developed the exact same faults it had originally.

Has anyone else come across this? Any suggestions will be gratefully received.

Thanks, Trevor

Sounds like dirty petrol, I would suggest draining tank and flushing out lines and pump, also clean injectors and change fuel filter.

Also ensure fuel pumps are priming and working and check for dry solder joints in fuel pump relay (behind ashtray) should be a white or green relay.

Hope this helps.

[madder93]

Suggest cleaning throttle body, for help look in previouse posts, it is in there some where. also try 700 faq site.

[Peter Milnes]

The most likely cause of this engine misbehaviour is that the fuel filter has become clogged (should be replaced fairly regularly). This may also be caused by the in-tank pump pick-up filter (sock) possibly coupled with a split in the pipe inside the tank (carries fuel to output piping). I had exactly the same with a Vauxhall Carlton estate several years ago which was cured by a new fuel filter.

All the best, Peter.