E30 randomly cuts out and won't rev over 4000RPM

[CoxyNz]

1988 E30 320i coupe with a 2.7 stroker motor. Owned for 2 years previous owner installed motor and ran fine for first year or so of ownership. It has a problem where it randomly cuts out for a split second while driving. As in the car will suddenly lose power and revs will drop for a split second and then keep running fine. Very intermittent with no warning. Sometimes if idling at traffic lights etc will cut out and die. Starts back up fine straight after.
Another problem is that it will refuse to rev over 4000rpm if full throttle. It will feel like I have hit a wall and the revs will drop and usually will backfire very loudly. A second or so after revs drop car will keep running fine but will refuse to keep revving over 4000rpm full throttle. If I am 3/4 throttle car will rev out to about 5000-6000rpm before cutting out.
I have replaced plugs, distributor and rotor, leads, crank angle sensor(adjusted to correct clearance), fuel filter, oil ICV, tested throttle position sensor, and made sure intake has no vacuum leaks.
I have a feeling it could be fuel pump relay or DME relay, The AFM or the ignition coil. Anyone that knows these cars well what would you think the probable cause would be before I bite the bullet and take it into a mechanic.
Any help appreciated thanks!

[superj]

a number of people have very similar issues to yours and i have not heard anyone say they figured it out.

our 88 superE does the thing where it hits a wall at 4k if you are floored. it doesn't back fire though, it just stops for a quick bit and then picks back up. and its anytime its floored and hits that rpm. no idea why and i haven't messed with it to really try and figure it out but if you accelerate just let off a little bit right at that point, it doesn't do it so i just try to remember to not keep flooring it there.

its not my daily either though but if it bothered my kids a bunch, since its the youngest son's daily, he might make a big deal out of it

[richardodn]

My gut feeling is the AFM. https://www.mye28.com/tech/rods_page...by_fr_wilk.pdf

[CoxyNz]

Might look into a new AFM then. Would I have to use a 325i AFM or a 325e AFM? What is usually used on the conversion? Cheers

[superj]

you won't use the 2.7 afm (325e). its always the 2.5 afm (325i) or an afm from an 80s to early 90s 535/735 car that ends in 027 on the pn. check what you have before you replace it though so you get a matching part.

the 2.7 afm is smaller then the 2.5 which is smaller then the 3.5

[CoxyNz]

My cars current afm has this Bosch part number: 0 280 202 082 the bottom number is: 1 286 615.9 Would you know the sort of engine/car that was off? Thanks

[superj]

realoem.com

type the pn in the bar and it will tell you what cars it came on

[richardodn]

My cars current afm has this Bosch part number: 0 280 202 082 the bottom number is: 1 286 615.9 Would you know the sort of engine/car that was off? Thanks

realoem.com

type the pn in the bar and it will tell you what cars it came on

That's a Bosch PN. You won't find it in realoem. However according to this page, it's for the 325i. https://www.programainc.com/bmw/volu...280202082.html

Before you replace yours, the page I pointed you to before has a simple diagnostic test you should run before throwing money at parts. I also saw above you replaced the main relay. Did you also replace the fuel pump relay?

[CoxyNz]

Replaced AFM and still no change... Next part will be relays and maybe ecu

[Kershaw]

https://www.r3vlimited.com/board/for...-stutter-fixed

Read this. Then switch to an aftermarket ECU. Haltech is a good option for those in NZ/AUS.