M20B29 hesitation at WOT above 5k

[Kershaw]

I think the OEM fix is a brand new engine harness. After 30 years the shielding doesn't protect enough and something about the harmonics of the chassis and a bunch of other electrical engineering stuff that I don't understand come into play.

A brand new engine harness was over $800 3 years ago, no idea what it is now. So yeah, Megasquirt is the answer.

[sert57]

I mean I agree, I'm not gonna worry about them any more, but - there SHOULD - have been a simple way to fix the issue...... especially since it has happened on others mostly stock cars.

The engineer in me is frustrated lol

gonna update the other threads soon.

Thanks again for all the help guys. Really appreciate it.

[Kershaw]

Glad it worked out. Don't worry about the AFM or the vibration damper, they were most likely not the issue.

Megasquirt is just the fix for this hiccup.

[2mAn]

you should update your cars thread. I like it. Cant wait to see what this does when its fully tuned

[sert57]

I ended up getting a decent deal on a DIYPNP unit, and now that it soldered together and set up, I can confirm that megasquirt did fix the problem. going to take it to a real tuner here in the coming days and get a dyno tune done.

It sounds glorious at 7K.

Happy the car runs right. Wish we could've figured out the issue with the motronic system but alas.

I'm still suspicious of the vibe damper. could have been the issue.

I'm also suspicious that the AFM isn't completely ignored in these operating conditions. I haven't seen any official documents, but it seems to be the general consensus.

[Kershaw]

Check the Vibration damper. With the years it gets soft and in higher RPMs may "confuse" the CPS.
Sorry that I intruded.

I have seen this before.

I thought I had mentioned it before, but I went back saw that I didn't. Definitely try swapping in another vibration damper.

[sert57]

Was thinking it may be a grounding issue with the ignition system. Added a ground to the cylinder head but it didn't impact anything.

Picked up a MS2 DIYPNP kit, so I'll be putting that together while trying to troubleshoot this.

Had a friend try his Karyln STI wires vs known good and the Karlyn seemed to be good.

[sert57]

Met a guy I knew yesterday who had a Baum CS2000.

First we double checked fuel system, its much easier with 2 people in the car. fuel pressure was good, went to about 50 psi at WOT above 5k. Fuel pump and FPR confirmed good.

CPS signal didn't seem to cut out on the BAUM at all. granted I do not know about refresh rates on this but there was no sign of it acting up.

It seems like theres an ignition issue causing the motronic to cut fuel. Currently suspect of my spark plug wires. When i built my motor I bought these spark plugs from FCP euro, never heard of the brand before. (https://www.fcpeuro.com/products/bmw...i-12121720529a)

Next step if to put known good ignition system from the old B25 on the engine and see if that helps.

[apostate]

Check the Vibration damper. With the years it gets soft and in higher RPMs may "confuse" the CPS.
Sorry that I intruded.

[sert57]

regapped the CPS to .4mm - no change
swapped ignition coils with a friend - no change

current suspicions:
1) CPS starting to go bad? It didn't ohm within spec, and it seems like these cars are getting to the point where these fail more and more. its just weird that it works in all other situations.
2) potential bad ground somewhere with the alternator?

I'm not thrilled about dropping $800 + to get this running right with a standalone when it could be a cheap easy fix, but I'm really starting to run out of ideas and am beginning to lean that way.

[sert57]

https://www.r3vlimited.com/board/sho...&postcount=107

Can you move the CPS closer than stock spec?

I tried regapping it a while ago. Originally it was close to 1mm gap and i adjusted it to 0.7 , but it didnt change anything.

That is the first time Ive seen that post, and its VERY interesting to me to hear his results. He is hte first ive heard of moving it out of stock spec to fix the problem. I will definitely try that soon and see what the results are!

[Kershaw]

https://www.r3vlimited.com/board/showpost.php?p=4474371&postcount=107

Can you move the CPS closer than stock spec?

[e30davie]

still running into this, any other ideas?
I feel like one answer is to give up and go standalone, but I'd love to solve it if i can.

A mega squirt plug and play ecu is a relatively cheap option and well regarded.

What does the guy say that you bought the "chip" off?

[sert57]

still running into this, any other ideas?
I feel like one answer is to give up and go standalone, but I'd love to solve it if i can.

[sert57]

Does the ecu make any sense to have gone bad? It worked fine before the build, but sat in the garage for a few days during the engine removal and install. I may try and find one locally to test.