91 m20 misfire when warm

[Caperix]

After my e30 was in the shop for a few months for paint I have been having issues with it. The car went in running great, came back with a crank/no start. I found the crank sensor had failed, replaced it with a fibi unit & the car would start but smoke. A compression test showed low compression on cylinder #4, pulling the valve cover I found a broken intake rocker arm. I replaced all the rocker arms & everything seemed to be ok. When driving the car started to buck & stalled. After a difficult restart it ran ok, but would miss under load.
I have checked the air flow meter for dead spots, the coolant temp sensor for proper reading & the fuel pressure for dropping off.
Before the car went to paint the plugs, wires, cap & rotor were replaced.
After the issue started I have replaced the o2 sensor, fuel injectors, using reman pink injectors, fuel filter, plug wires, one broke when pulling off, coil & tps. I also cut the cat out as the damaged rocker had clogged it.
The engine starts fine cold but as temp increases is more hesitant to rev without misfiring. It will occasionally drop revs at idle, when this happens all the gauges drop for a second.
Any ideas on this issue, I am starting to lean toward a dme. I have attached the data from my launch scan tool read from the dme, nothing looks too off to me.

[It's Soda Not Pop]

What does your cluster do when it bucks?

[It's Soda Not Pop]

You could have a failing Main Relay. Mine did this when it got hot. It work sometimes, but toward the end of it's life my car would buck and the gauges went dead for a sec. I replaced the main relay and this solved most of my issues.

[hasa]

So paint shop employee destroyed the engine by doing stupid things, probably donuts on the parking area. And now it is your turn to repair the engine?

[Caperix]

The body shop claimed they never drove it & mileage in the cluster only went up a few miles. It may just be things catching up to a 32 year old car.
I have only noticed the cluster drop out when revs intermittently drop at idle & not when the miss when revving occurs. The main relay could be a possibility though.
The issue when revving feels like a rev limiter, it pops & will not gain rpm, this can happen as low as 2000 rpm. When cold it will rev fine. I am going to try out one of the cheap oscilloscopes to look at the crank signal, the injector signals & the coil signal to see if any of them are going something strange. The tach in the car does not reliably work & the data stream to the scan tool is to slow to know if the new crank sensor is doing something funny

[It's Soda Not Pop]

Also do the stomp test and get what codes are being thrown. This could help maybe point you in the right direction. But if you have fuel and spark and the AFM is good. This sounds like a timing issue. Or the DME is loosing signal. The main relay may be your culprit or the CPS.

[Caperix]

I have been using my scan tool for faults, it is showing none stored. A stomp test to make sure there is not something it does not read could not hurt. The oscilloscope I ordered should be here by this weekend. I am going to scope the crank sensor, fuel injectors & coil to see if I can see what is dropping out. I also plan to double check compression & hook a timing light up to see if its jumping around. I would think the main relay dropping out would cause me to loose the data stream from the dme, but I may have a spare to try as well.

[ADEN]

If it was me i will go replace DME first (as the guys mentioned above) if still, Test each wire of the 22 years old harness for continuity to 55 pin last week i pulled mine and wire insulations were super hard and brittle with cracks making some intermittent shorts specially around the area of the tps and evap solenoid under the intake.

[Caperix]

I feel like I am making some progress. The first time I back probed the crank sensor with the scope I could not get the issue to occur. Removing the probes caused it to act up again. I reinstalled the probes & could get it to act up. To me it looks like the scope is picking up something in the crank sensor signal.
The pins are not loose in the back of the connector. I need to chase the wiring to see if there is some damage any place.
Has anyone had any crank sensor wiring issues, is there a common spot in the wiring for breaks?

[Caperix]

I feel like I am making some progress. The first time I back probed the crank sensor with the scope I could not get the issue to occur. Removing the probes caused it to act up again. I reinstalled the probes & could get it to act up. To me it looks like the scope is picking up something in the crank sensor signal.
The pins are not loose in the back of the connector. I need to chase the wiring to see if there is some damage any place.
Has anyone had any crank sensor wiring issues, is there a common spot in the wiring for breaks?

[ADEN]

Are the teeth clean?
Sensor secure?
Check for wheel for wobbling when revving, harmonic balancer is 2 wheels connected by rubber between them the rubber deteriorates causing the trigger wheel to wobbles.

[Caperix]

I found a small amount of rubbing on the water pump pulley to the crank sensor wiring. I pulled the wiring back & cable tied it to prevent movement. The issue has not occurred since. I will order a new crank sensor to prevent any future issues from the wiring. Strange it only occurred when revving warm, but glad it seems to be fixed. Now I just need to set up new exhaust from the manifolds back from the failed cat