Too Much fuel causing misfire

[MaxShats]

I have a 1979 BMW 733i that was running great. Recently I started it up and there was a misfire so i pulled the plugs. They were black so I bought new ones and it still had the misfire. I drove for 15 minuets went home and pulled the plugs again. They were already black. I tried messing with the MAF to lean it out but that did nothing so I bought a new one. The new one does nothing. I did some research and found that the fuel pressure regulator might be the problem. I bought one, installed it, but the misfire was still there. I redid the timing to manufacture spec and still nothing. I check the valve clearance and that was also fine, and my compression is normal. I also have black smoke coming out of my tail pipe. I'm really just lost at this point and do not know what to do.

[kojo96]

It sounds like the car is running rich, it's most likely your coolant temp switch located on the drivers side of the block. Lower near the throttle linkage. It has a water hose going through it. The problem is they are no longer available, had the same issue on my 79 733i but got lucky and was able to buy the last OEM new sensor from a local dealer. Pull it out and test resistance on it.

[MaxShats]

Thanks for the advice. Just checked the sensor and I have no ohms resistance while cold, is that what I should be at? I’m also reading 0.2 ohms wile warm. I found another temp sensor on the top of the motor which also reads no ohms resistance while cold and 0 while warm.

[Hit Man X]

I have never experienced a misfire from overfueling. You may have a cracked cap or tired cap and rotor. Wireset could be junk too. Kingsborne makes great sets still for us.

Ljet and Motronic temp sensors are NTC units. Figure about 250 ohm hot and about 2500 cold as rough measurements.

Post a pic of which sensor you tested

[MaxShats]

I replaced the Cap and rotor and the spark plug wires recently so I do not think that it is spark related. I will post a pic of the sensors that I tested when I get home. Thanks for the reply.

[MaxShats]

Ok so I just went ahead and replaced both sensors that I tested and I am still having the same issue. I ordered a new L-Jetronic ECU and hopefully that will fix it.