M20b20

[BATTS91]

Right ive gad to do an engine swap on a 320 , like for like m20b20 . Having a missfire problem .
Got engine in ect , wouldnt start at first due to earth strap to sump being shite . Then it started up fine revving ect .
Had to get the car parked up outside the workshop so drove it but it kept just dieing under load at low revs .

Then the next day missfire !
Ive swapped the following with no difference and checked for air leaks .

Coil
Tps
Icv
Maf
Fuel lines
Plugs
Leads
Dizzy rota clean
Fpr
Alog with bypassing fuel filter check fuel in and return both seem fine .

My mind is now baffled , any help suggestions would be apreciated

[Speedtouch]

Are the engines year-for-year swaps, and which ECUs were originally fitted to each, e.g. 0 261 200 172, etc.?

[BATTS91]

Both facelift engines . And i know 100% the engine ran fine in another car .

261 ecu i beleive .

Only thing i can think of is a crank sensor but dont have a spare to try .

[BATTS91]

Or 081 .

[Speedtouch]

I would try a compression test - all six pots should return roughly equal values of around 180 psi.

Are you using the ECU that came with the new engine, or the original?

[BATTS91]

The original Ecu and tryed another ecu same code and tryed a 2.5 ecu on the off chance but was still the same .

Ill see if i can find a tester

Thanks Apreciated .

[Speedtouch]

Have you followed the initialisation procedure, i.e., let the engine idle for at least 10 minutes to enable base idle settings to be learnt, switch off, then take it for a drive throughout the rev range?

This ensures full data transfer from the EPROM to the processor.

Also, do you have fresh fuel in the tank? Modern fuel goes stale very quickly.

[BATTS91]

Yes ive drained all the fuel and put fresh in.

The missfire is pretty bad and couldnt be driven , even if its this bad still let it tick over? even tho it ran ok for about 15 mins previous night as i said ?

Thanks

[Speedtouch]

Or 081 .

The 0 261 200 081 ECU was an early Motronic 1.0/1.1 ECU used in the pre-facelift 325i - unlikely to be suitable for an M20B20.

You could try the steps outlined here:

http://www.e30zone.net/e30zonewiki/inde ... oubleshoot

[BATTS91]

yes motronic im sure .
ill have to double check tomorrow when up the workshop .

i think it maybe a yellow sticker but my mind is shot from it all now so ill get exact details tomorrow .

Is there a code ending in 083 ?

Thanks

[BATTS91]

woken up abit now think its 381 .

[BATTS91]

Is there a way to test the crank sensor at all ?

Thanks

[Speedtouch]

The 381 ECU was prone to failure of the diodes in the idle control circuit - you're better off swapping it for a 172.

The CPS is just a coil of wire - use a multimeter to check the resistance across it; it should be around 500 ohms, according to the Zone Wiki:

http://www.e30zone.net/e30zonewiki/inde ... ion_Sensor

[BATTS91]

Ive tryed another 381 ecu that we had in the workshop but still the misfire , The only thing left is the cps .but we only have a multimeter so can only check if its completely gone or not , which isn't the case as it still fires up , well sort of anyway .
Is there anything else i should check or try before ordering a new cps from euros? .

Thanks in advance .

[Grrrmachine]

Have you been daft and not plugged in the AFM properly?

[BATTS91]

100% buddy . Even tried another maf . .

Most of the time it will only rev to like 2k with heavy misfire .
Im out of all ideas apart from crank sensor really .

Thanks

[Gunni]

Sounds like a massive vacuum leak in where it leans out with more engine speed.

[Speedtouch]

Was the engine known to be a good runner in the donor car?

I would check the compression first, then ensure that the cambelt is properly fitted - check the timing marks align, etc.

[BATTS91]

All sorted . Was the crank sensor .
And the engine came out of a pals that he converted to 2.5 ;)

Thanks guys .

[Speedtouch]

Congratulations on getting it sorted.

[BATTS91]

Thanks . I maybe in touch soon for a chip as its slow as fook ! Too used to m50 power lol .