My 94 BMW 325i convertible has a miss in it?

Question

My 94 BMW 325i has a slight miss somewhere around 2500 RPMS. If you give gas, or let off the gas, this miss goes away. But if its held steady at 2500 RPMS, the miss stays. Any clue what this could be? There are no lights that come on, and its not the transmition... The car is near flawless with only 100K on it.

Answer 1

There is no way for us to tell you, for sure, over the internet, but a likely possibility is ignition related. An ignition weakness will typically show up with the symptoms you are describing, although there can be mechanical causes as well as computer control. The first place I would start, if it were at my shop, is monitoring the ignition coil with a lab scope while duplicating the concern. A weak coil will show up very easily with this test, and it can rule it in or out. After that I would perform secondary ignition waveform tests to determine if the problem lay in wires or plugs, and if they were okay then I would go to sensors that help control ignition, like the crankshaft and camshaft sensors, ignition module and powertrain control module. If these test well, or even if the crank or cam signal looks bad, then the possibility of mechanical issues can be pursued, like a cracked flywheel that causes the reluctor teeth to be in the wrong place and therefore causing the correctly working cam or crank sensor to report improperly. Again, these are just educated guesses based statistically on my experience in engine performance, but I think that they are an okay place to start for the facility that evaluates the concern.

Answer 2

i own a shop,and id say it probably needs s good minor tune up on it,a new set of plugs and wires and a gas filter and maybe a new air filter would probably make that one run like new,since its not a constant miss, its just a tune up related problem with it,good luck i hope this helps.