What the F*#K is wrong with my e30??

[=======Live Fast!]

Hey guys. Hope everyone's been well. Haven't been on here in a hot min. Here's the deal. I'm getting a stutter/bogging in the acceleration under load starting at around 3800 rpm and up. Not so much in 1st through 3rd. Very noticeable in 4th and 5th Haven't driven the car in forever as I was building an engine for it to go back in but am recalling that it was doing this before as well. This is what I've went through so far.
New plugs, wires, cap and rotor. Checked the coil, good. Swapped out a known working afm, did't help. Swapped out a TPS today. Isn't that either. New injectors, new fuel filter. Wasn't that either. Last thing would be the pump and that covers fuel. It has new fuel lines as well and new hoses on the whole engine so no vacuum leaks. My buddy is thinking maybe it's the harness. Any thoughts? I've read other posts that seem to cover the same topic but never get resolved. This is making my head and my pockets hurt.

[zwill23]

Sounds to me like a CPS problem. That issue is particularly common when converting to megasquirt, but it impacts the stock ecu similarly.

[=======Live Fast!]

Brand new crank position sensor.

[lukeADE335i]

With all that replaced, check the C191 connector under the inlet manifold - you might find the terminals are corroded.

https://www.e30zone.net/e30wiki/index.php/C191

With all the injector & sensor changes etc. have you reset the DME so it deletes all error codes and goes back to base maps? If not, give that a try - when I swapped my CPS last weekend, the car wouldn't run right until I reset the DME as it had been compensating for the CPS being on the way out.

Failing that, swap the DME for a known good one.

Reading your post above - you mention the fuel pump as the last thing, I presume you've replaced it?

[=======Live Fast!]

I haven't swapped the fuel pump yet. I'm going to swap the DME today and see what happens. Interesting thing about C191...Mine was hardwired in at some point so you might be onto something. Thanks for the info.

[=======Live Fast!]

Swapped the DME...not that either

[ZeKahr]

O2 sensor?

[lukeADE335i]

Swapped the DME...not that either

Sounds like the electrics are pretty sorted (assuming the C191 is ok - check that the joints there aren't corroded / have bad contacts), you can check the O2 sensor by unplugging it, the car should run ok, just a bit rich.

I'd give the fuel side some attention now. Could be a leaking Fuel Pressure Regulator, but I'd think the most likely culprit is the fuel pump.

[twright]

Put a fuel pressure gage on the line going to the injector rail. See if the pressure drops when the "stuttering" occurs.

[=======Live Fast!]

Just swapped out the fuel pump with a good one...wasn't it. Unplugged the O2 to run it and it's still doing it. I'm going to try a new crank position sensor tomorrow and I'll report back.

[Khoronzy]

Check that the bottom of the rubber inlet isn't torn between afm and tb. It tears where u can not see it. And if u just look u won't see it.. take it off and look!

[peytonracer4]

you're sure the timing belt isn't off by a notch maybe? unlikely, but just brainstorming.

[=======Live Fast!]

New crank position sensor today just to make sure...not it. And Peytoracer4 this had been happening on my last 3 engines I had in there. Also it was a symptom that used to only present itself at higher rpm and gears and now it's lower gears and rpms. The wiring harness is literally the last thing that could be done.

[lukeADE335i]

Hi Live Fast! Did you end up sorting your issue? Just interested if you managed to resolve it after swapping so many parts.

[E30 Wagen]

Maybe back pressure from a clogged exhaust system?