Help and advice still needed!

[Mr Tank]

Hi

A little while ago I asked for help with a problem with this winters 350i project!

It has a flat spot around 1500 and engine dies if you hold it there. Push on and it goes like a train.

Following your help I have now changed/fitted:

New Air filter.
New Airflow meter.
New Air pipe from plenum to air flow meter.
New Plugs.
New potentiometer.
New dist cap and leads.
Replaced by-pass valve in back of plenum

It's better but still does it!

Any more ideas!

Andy

[B-Reight]

Andy, i recently read somewhere that if the alternator wiring is run close to the distributor, the emf can effect the distributor pickup at around this RPM, meaning the ecu does not see the correct spikes and the fuelling goes to pot.

[Wedg1e]

Portable 'scope on the trigger lead to the ECU would show that up.

[Hippy]

Have a word with leorest whos on here , this must be about 8 years but his 350 went through a stage of doing something similar if memory serves. A dry joint in the ECU was the problem if I recall correctly. Leo resoldered all the joints in the ECU and it sorted it out.

[Mr Tank]

Hippy

Thanks for that. I will try my spare ecu at the weekend.

Now any more ideas anybody!

Andy.

[grahamw48]

The distributor itself may be worn.

When I first bought my 400, that was discovered to be the fault when all other possible causes had been eliminated (by Falcon Engineering, who maintain rally cars etc, up near Wedg1e).

Replacement distributor sorted mine for good, though possibly only advance springs, etc needed.

[Mr Tank]

Hi

Started the car today, and now its run like its over fuelling, very simliar to the simptons it had at around 1200 rpm but no at all reves. The cold start injectory is disconnected so its not that!
Any more ideas!

[Wedg1e]

Yep, still counds like an ECU issue...

[Mr Tank]

Hi

Just seen all my typing mistake err! Have to go to bed and get some sleep!!

Andy

[Wedg1e]

Mr Tank said:

Hi

Just seen all my typing mistake err! Have to go to bed and get some sleep!!

Andy

Ah shag it, I made one too

Did you try spare ECU? If it didn't fix it then either you have two fuackered ECUs or the fault is more fundamental.

[Mr Tank]

Hi

Was going to try my spare ecu at the weekend, if that doesn't work I will try the one of no 1.

Andy

[honestjohntoo]

Mr Tank said:

It has a flat spot around 1500 and engine dies if you hold it there. Push on and it goes like a train.

Run the engine for several minutes either side of your flatspot, kill it and inspect the plugs for rich, normal or lean running. Its gonna be a close-run thing, but if lean or normal you can ignore overfuelling and test for rogue air leaks into the plenum chamber. For rich just test the various components that modify mixture. Dont overlook the breather system too. You probably know where to find testing literature. No point in buying components speculatively without some clue as to faulty or not.

And, as already suggested, the ECU may be a usual suspect.