1986 BMW 325/325e Electrical Issues!!!

[JacobDuarte]

Hello everyone I have a 1986 BMW 325 that has the economy 2.7L engine in it manual transmission 84,000 miles
Story is Lady bought the car brand new in 1986 she drove it until 2002 when she "blew a coolant line" I bought it last year in 2021 not running.
I started by replacing everything outside of the engine resealed everything other than the head gasket did all belts all hoses.
Got the car to run but very rough turned out my fuel injectors were clogged. Bought new ones put them in ran fine for 30 seconds then instantly bad. I clogged the new injectors instantly.
I then proceeded to replace the whole fueling system including all lines front to back a whole new gas tank and I had to put a DW400 pump in it because the OEM was $600+.
The car was running and running well I took it down the road drove it back parked it still running opened the hood and the OEM coolant started rapidly bubbling out of the reservoir.
Come to find out there was a clog in the thermostat housing going to the throttle body I capped it and removed it.
Drove the car for 2 hours up and down the road was perfectly fine bleed the coolant and it stopped bubbling.

The problem I'm running into is that the car only runs nice when I have the coolant sensor for the ECU unplugged. If its plugged in it constantly hunts for idle and runs really choppy under load.
The other problem I'm having is the only readings I'm getting on my dash are MPH and my gas gauge. Tach reading coolant reading don't show anything.
I have tried to diagnose it I know I'm getting voltage at all of the 5 cooling sensors and to my understanding the tach comes from the sensor on the harmonic balancer and that all checks out I think.
I am very bad at wiring and electrical I try my best to learn but its very confusing.
If anyone could help me or give me some ideas that would be much appreciated thank you.

[tomstin]

A few things to get you started. Wiring diagram for your car here: http://wedophones.com/Manuals/BMW/

Idle FAQs that should help you verify the wiring to the various temperature sensors: http://www.verrill.com/car/e30_idlefaq.shtml

Many of your dash issues are probably caused by a bad SI board which is part of the instrument panel. These folks can help: http://bavrest.com/index.html

For the tach, again, probably an issue with the instrument cluster but the ECU gets the tach signal from the speed sensor on the flywheel. On the transmission bell housing there are two sensors, one is a "reference sensor" (looks for a tang on the flywheel). And the "speed sensor" which basically counts the teeth on the flywheel.

Hope that all helps. Sorry, but no easy answers.

[JacobDuarte]

Perfect thank you I will start with that I'm almost at the point where I'm gonna bring it to a BMW shop and have them figure it out haha

[82eye]

your coolant temp sensor probably needs replaced as well. it also causes a poor running condition if bad.