I just recently purchased a 1993 325i that has a problem. The enigne at first would not crank. Replaced the battery... still wouldn't crank. Checked the spark plugs... dirty and very black on the tips and replaced. Checked the oil levels and was low and also very dirty and was also replaced... (previous owner must not have done the work!)... Now at this point it would crank but would stall immediatly after you let go of the gas. Did some poking around and found that the vacuum line to the fuel injectors was completely blown and replaced it. Tried to start the car again and it would die like before. Disconnected the air flow sensor and the car would idle (horrible tho!) but showed another problem. Now there is a loud popping sound that comes from somewhere in the engine bay. one theroy that I have is that it might be a dropped cylinder.
But we hope not. I do have a spare motor but am trying to avoid using it unless it is a last resort.
I am posting this to see if I can get any advise on what would be my next course of action to take from this point. Any advise would be greatly appreciated and extremely helpful!!!
Do a compression test to rule out things like: Skipped timing chain or bent valves.
Might be as simple as spark plug wires hooked up in wrong order. Those would all allow misfire in the intake. I'm sure there are other reasons but this is somewhere to start. It would be nice to find compression is good, then all you'll need is a tune up etc.
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