E30 M20 2.7l stroker misfiring? Confused...

NYSpeed Automotive
1

I just picked up a 88 325e (super eta) with the “i” swap (Head, intake manifold, throttle body, and 173 ECU). The PO also added the M30 AFM and M30 Injectors. He said he was running a “custom” Mark D performance chip.

When I bought the car, it was making a bad vibration. I took the car to a shop and had them check it out and it turned out that the PO didnt have the #4 injector clip plugged in correctly. One they plugged it in correctly, it ran perfectly…almost.

On my way home from the shop, the car started to misfire. I use the term misfire loosely because Ive never had a car do it to me before so Im not 100% sure what it feels like. I will be driving the car and all of a sudden it hickups and then it will go fine for a second and then it will hickup again. Im not sure if its misfiring or detonating. Again, Ive never been in a car with someone and have a car do either of those and someone tell me ‘thats a car misfiring’ or ‘thats a car detonating’. the problem starts ~3500rpm and will do it every ~200rpm after that. It only happens when the car warms up and never does it under 3k. The car is running 89 octane right now so Im wondering if it has to do with the gas. Any info would be great.

Im sorry for the newb questions but I want to try to figure out what I should do next to get rid of the problem and prevent any damage. Im still new to the whole E30 scene excuse my ignorance.

2

Could be a number of things:

  1. bad fuel
  2. crank position sensor?
  3. how is the cam timing?

do you have a hand held scope?

3

Im kinda thinking its bad fuel too. Im not sure how the cam timing is. Ill check into that. I dont NOT have a hand held scope either. LOL. Im going to go get some octane booster and see how that goes. Also, what would make it only do this when the car warms up? When its cold, it runs fine.

4

ugh my car is doing the exact same thing…

lmk if you find the problem, and vise versa

5

Check your coolant temp sensor as well.

Ohm readings should be as follows:
At approximately 66-70 degress, you should see about 2200-2700 ohms across the poles
At 174-178 degrees, 300-360 ohms.

For a quick test, go to radio shack, get yourself a 330 ohm resistor, and plug it into the CTS connector when the car is warm. See if that changes anything,