Warm misfire from idle to 3k

[blackflag]

So I just finished up swapping an m50b25nv/zf310 into my e28 and so far, everything has been amazing. There is one issue however, that is bugging the hell out of me. After the motor warms up it doesn't fire on all 6 unless I get it over 3000rpm. It also runs just fine at very low throttle input. No check engine lights are triggered and I can't get it to do the stomp test, but the light does function. I have been swapping coil packs but the issue doesn't change. I was thinking maybe my tps is going out but wanted to consult the gods of m50 swaps first.

[trackjunkie21]

How do you know it's a misfire?

[blackflag]

Well, its down on power a lot and sounds like a Subaru. But I was just guessing.

[iceman]

When I had a TPS go out on my brothers NV50 it was just causing weird idle rpms, but that is not a bad idea. Unplug it and see if changes. I was going to suggest plugs or coils. Does it turn over and start easily?

You should also check:

Ground wires
Vacuum (You wrote that it idles nicely though)

[E30ruben]

Don't mean to bite off this thread but I have the 91 318i I just bought and it idles somewhat perfectly smooth but from idle to about 2k-ish it feels like a misfire. I put brand new spark plugs and it's better, just not smooth. Even if I rev it up to 4 or any rpm and hold it there, feels the same.

[iceman]

^Could you describle the feeling in more detail. What does it sound like when it is idling? When you say misfire, do you hear poping noises or does it feel like it is just cutting out/low on power?

To Start, Check:
Ground wires
Check vacuum hoses

[hoveringuy]

Sounds like a vacuum leak. Not misfiring when cold because it's running richer. Leans as it warms up and with a vacuum leak it's getting TOO lean and misfiring.

Use 3 feet of flexible plastic tubing attached to a propane source, probe the end around the intake manifold until you find the leak. RPMS will increase.

[E30ruben]

^Could you describle the feeling in more detail. What does it sound like when it is idling? When you say misfire, do you hear poping noises or does it feel like it is just cutting out/low on power?

To Start, Check:
Ground wires
Check vacuum hoses

Feels like someone is punching the car from under kinda. It's not that bad but just bugging me. I'm thinking it's a vacuum leak but idk could be something small. Raced my friends 318is and we're neck in neck

[blackflag]

So far I have swapped a good coil on cylinders 1-4 but still having the issue. Plugs are all brand new and the grounds look good. Ill check for a vacuum leak when I get a chance. And no worries about tagging on the thread.

[blackflag]

I managed to get under the hood and check things while this issue is happening. I pulled the plug on coilpacks number 3 and 6 and there was no change. Are there any systems that deal with these 2 cylinders individually?

[trackjunkie21]

Yes, the coils themselves.

[weaksauce]

coil packs are bad
i had a customer car with the same symptoms a few weeks back.

swapped in a good coil pack and it went away and ran great afterwards.