E30 M3 Power Loss - help required!

All sugestions welcomed - the problems is this:

Car can suddenly loose power, either when pulling away or on
a steady throttle (press the throttle down and nothing, car dies
and will not pull away). Back off on the throttle and go back on it
and it will suddenly start working again!

It did this several times this morning and annoyed the hell out
of me and it could be potentially dangerous.

Other things I've noted are that it prefers to do it more in damp/
wet weather or after a fuel stop - both of which I had this
morning!! This problem is driving me up the wall as it's been
going on for nearly a year (though it was fine in the summer).

Parts that have been changed within the last year are: O2
sensor, ECU, distributor cap and rotor, injectors, airfilter, air
flow meter and plugs. Fuel Filter has not been changed but will
be this weekend.

Could it be the TPS or something else electrical? TPS does
'click' when moved away from idle position - does that mean its
working OK??

Thanks for any help.

Mark

Thanks for the reply - a fuel problem is my no 1 suspect after all
that was replaced last year!

The car has sat around for a while in the past prior to me
buying it in 2004 so maybe theres a lot of crap in the fuel tank
which filling up makes worse! It's in for an MoT and Oil service
on Saturday and the fuel filter will be changed at that time. If
that doesn't help I'll have to start looking at other things.

Mark

AFM a good possibility, as well as blocked filter,
worth checking the in-tank pump under the rear seat,
also worth checking the coil, and what condition are
you plug leads in?

Also worth seeing if you have water ingress above
the glove box just in case the ecu is getting a bit
damp!

I have a spare working AFM if you need one.

Dave

AFM is less than a year old (I've still got the old one - it's a Sport
Evo so it uses the different AFM). The leads were replaced
within the last two years.

I might try swapping in some of the old components one at a
time and see if there's any difference if this problem continues
after next weekends work.

Just spoken to Nigel Moesley and he suggested trying
disconnecting the barometric sensor or the fuel damper on the
fuel pump under the rear seat.

Keep the suggestions coming.

Mark

Quote from "hardtailer" ( I guy I know from the german S14 crowd)

Anyone suspecting fuel delivery problems should check wether the problem has been solved by the changing of the fuel filter alone.

One check that can be done on the fuel delivery is the following:

- undo the fuel return line from the fuel rail that sits on top of the engine
- put a length of fuel hose on to the rail and the other end in a measuring container
- pull out the fuel pump relay from behind the cover behind the expansion tank
- bridge the contacts in the socket in order to operate the fuel pump.
- measure the quantity of fuel that's being delivered. It should be 750cc in 30 seconds
- if it's less you could perform the same test directly at the pump underneath the car on the left hand side where the pump sits. If the flow rate is ok there (should be slightly more than 1.5l/min) then you have a clogged filter. If it's too low again you need a new pump (or 2 as there is a 'pre-pump' inside the tank)

to check the fuel pressure one should hook up the pressure tester in the return line. It should read at least 3.0 bar. If it doesn't, either filter is clogged, or pump/pressure regulator are defective.

I had a similar problem once. The culprit was a Motronic with bad solderings for the transistors that run the injectors. Look for hair cracks with a magnifying glass and good light, resolder and you're done.
Quote end.

Mark

I would take it back to Nigel and insist he gets it sorted as it has nevet run right since you bought it. He'll know this because of the amount of calls you have made to him and what has been replaced.