QuestionI also wanted to tell you that after I get it to kick in and run at a steady speed it will drive fine but will pop(backfire) ocasionally as it drives,but if i evenstep a little more into the gas it bogs or backfires until i push it through again.also it seems like it runs better if i keep it in a lower gear.But as soon as I stop at a light I have to rev it up and push it to accelerate again.In my not qaulified opinion it seems like the car is running to rich,so if I rev it up i burn off the excess fuel and it leans out enough to accelerate but then starts to back build again.on most cars of another make I could simply adjust the air fuel mixture.why cant i on the bmw?is it because it is all computer controlled?your answer earlier is awesome amd helpfull,I am just trying to understand the problem.
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rough idle,missing on take off but if i push through it catches and takes off like a rocket.I have replaced plugs and done away with cats so I now its breathing like a monster.it backfires constantly at idle,if I disconnect the mass air flow connection it will idle down and usaully not backfire at idle but will hesitae and back fire on acceleration until i push it hard.then it will run ok but still backfire.
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Hi Martin!
I will not concern myself with the legality or the reason for your removing the catalytic converter, but did you leave the 02 sensor intact and are its wires still connected? If the 02 sensor is still connected and working properly (as verified by a scanner that sees data stream of 02 sensor voltages) then the problem or problems is/are elsewhere.
The rough idle could be a simple thing like a defective idle air valve or vacuum leak. It could also be due to a bad MAF.
But misfiring is another thing. It can not be bad ignition coils since it also runs like a rocket sometimes, you say.
Worst case scenario is a bad DME (engine control module).
The best thing for you to do is to hook it up to a scanner that can work on non-OBD cars like yours---read faults, look at adaptation values which is long term/short term fuel trim in normal english, verify 02 sensor voltages, look for cylinder misfires. In other words, look for faults being set by your lovable monster.
Then tell me more about it. I would not recommend any parts replacement not unless you have a lot of money to throw away.
AnswerHi again Martin!
Thanks for the update. You are absolutely right that Beemers
being highly computerized do not lend itself to repairs that you can do in most other cars.
Based on your previous comments,it can not be due to a bad throttle for although it can bog you down, it will not cause a backfire. While a leaking injector can in an extremely rare case scenario cause a backfire, it would do so constantly so you can discount this too. Bad wires or ignition coils will also make the engine run bad every time but not necessarily backfire. A bad cam sensor would make it stall which you have never mentioned.
So you are left with only a few possible problems: MAF, 02 sensor, and DME. All three are interconnected and can really mess up your engine's operability. I may be wrong, but that is my reasoned opinion.
And all this presupposes that nobody has messed up with your timing chain/belt, or if it has damaged a tooth and therefore gone out of timing.
I hope these comments help you diagnose your car.
Tino
