M30 swap. Ok in midrange but lacks power & leans off at

[suckmyrockets]

Thinking caps on please as ours have almost worn through.

The donor for our project was a 1989 535i Sport that had a Fritz Bitz ss manifold & exhaust system already fitted. Supposedly good for 220bhp on an accompanying dyno sheet.

It seemed to run fine and after the transplant still looked that way. Until track day which has left us a bit underwhelmed and bemused. And as already mentioned, much scratching of heads.

The car feels as though it has plenty of grunt in the midrange but won't even contemplate revving to the red line under full load. She's leaning off at the top end as can be seen from probe up the exhaust and the state of the plugs.

We've got to the point where we believe that there could be some sensor, ECU, or combination of the two.

Our latest thoughts are around the lambda sensor. Or rather the lack thereof as there wasn't one fitted to our donor car due to the aftermarket exhaust.

Should an '89 car be fitted with a lambda? GSF & Eurocarparts both list one. If the lambda is removed then does some electrickery need to be performed on the ECU to compensate?

Any thoughts will be gratefully received.

[johnl320]

May sound silly but have you got the fuel lines on the right way around. Feed needs to go straight to the fuel rail not the pressure regulator ( A fairly common mistake)

Make sure the inlet manifold isnt receiving any unmetered air from places like the pipework from the brake servo, large hose from AFM split, vacuum pipe to fuel pressure regulator.

HTH
john

[leeparkes]

89 car wont have a lambda.

M30's start to run out of breath anyway at around 5k but they will still keep pulling fairly strong to the redline.

Mine was leaning off high in the revs and it turned out to be the air flow meter flap, the spring was too tight.
Pop the plastic cover off the AFM and loosen the spring by one tooth on the cog (you will know what i mean when you see it. ) use a screwdriver to click it across, see if that helps
But once you have loosened the spring it will run a bit more rich at idle, which then means you have to mess with the mixture screw,cant remember which way the mixture screw is turned to lean off though, iirc its anti clockwise.

If the fuel system up to scratch? Ie,Fuel filter, Bristol_jer on here took one off that was date stamped about 20 years ago.

Do you know what the injectors are like?

[MJJ_ZX6RR]

Don't worry about the lambda being there or not. The M30 in mine came from a 92 cat equipped car, and simply unplugging the lambda puts the car on a default fuel map that runs perfectly.

I agree with those above, sounds like fuel starvation at higher revs - so fuel filter, fuel pressure regulator, horribly dirty/blocked injectors or a custom chip in the ECU that leans the fuel mixture horribly.

Martin.

[suckmyrockets]

Thanks everyone for your contribution. Very useful suggestions, appreciated.

.No fuel filter fitted you our E30 (on the list)
.Tried another AFM with similar results
.Fuel lines are the right way 'round (we already made that mistake!)

It's had a cam shaft recently & shows good compression.

We're not convinced that we're getting a strong spark at the top end so the coil is going to be swapped out for a high output one. We're also going to pop the injectors out for testing/cleaning.

Will post when we finally find the cause but you'll probably hear the fireworks and champagne corks, especially Bristol_jer

[Jhonno]

Cap/rotor?

[johnl320]

New camshaft timed up correctly?

[e301988325i]

Check the TPS is registering full load as it should, gentlemans bet on it.

[suckmyrockets]

Distributor cap and rotor will be replaced along with the coil.

On the note about timing we investigated the sensor on lead #6 and appears fine short of replacing the lot and they're not particularly cheap.

TPS, e301988325i? Do you mean Throttle Position Sensor?

Thanks again for the suggestions - please keep 'em coming as I'm sure someone on here will fix it before we do!

[e301988325i]

Yes, IIRC the TPS is upside down on an M30 compared to an M20, so middle pin is common, at idle, middle and right pin should have continuity, at high load (throttle open 75%+) left and middle pin should have continuity, I suspect the ECU is not getting the high load signal.

When I got my car (stock 325i) theTPS was not registering either, fixing it cured my poor idle and must have released 10bhp!!!