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Is inconsistant performance a BMW trait?

1358 Views 4 Replies 5 Participants Last post by  paul330ci
It has now been 2 weeks since I bought my first BMW, a '95 325is automatic. I am getting used to not having the raw horsepower type accelleration I have had in other "sports" type cars but the inconsistant performance is driving me crazy. Just to make sure I wasn't crazy I started timing my of the line accelleration. With the A/C off, and trany in "D" I get 0-60mph times anywhere from 7 sec. to 10 sec. Sometimes the car feels like it has a turbo when it hits 3000 rpm and other times it feels like there's a freakin 6,000 lb boat tied to the rear bumper. Sometimes the car pulls strong as hell to 6500 rpm and other times I watch the tach act like its a second hand on a watch. What gives? No check engine light or engine codes and no other codes body computer or otherwise. I have noticed that sometimes when siting at a stop light with the A/C on the engine almost stalls when the A/C compressor cycles on, to the point the rear end raises like you put the car in park. Since I am experienced at modifying/performance tuning the american fuel injected sports cars, I assume I can use that same knowledge to some extent such as checking for adequate fuel pressure, ignition power, air flow, timing advance, etc. I am not aware yet if there is anything special I need to learn about the BMW engine though. I don't want to just give up and go back to a "V8" powered sports car yet as I do love the way the car drives and handles and since I am looking at graduating to a 2001 330CI in about 6 months I don't want to put a bad taste in my mouth about BMW's and miss out on driving a new model. Any help or suggestions from the seasoned BMW pros appreciated.
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That does sound baffling. The only thing I can think to suggest is to bring it to the dealer, and have them run diagnostics on the ECU and see if there are error codes, etc. There may be a fault that is causing the sloppy performance. If this doesn't do the trick, maybe consider upgrading the ECU software via a Shark Injector or equivelent. I dunno, there are people on this board that know a lot more about this than me.

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Doesn't sound right. I certainly don't notice inconsistency in my 330's performance... although I have never sat with a stopwatch to measure scientifically.

My ass-dyno tells me it's consistent, though.

I also don't have step, either, so I don't know what variables that throws into the equation.
I'm guessing that on your slow runs, your torque convertor never catches up to the engine revs, and you get lackluster performance. Instead of flooring the gas right away, make the pedal motion a smooth sweep until your foot is on the floor.

Another thought is that the engine cuts back on fuel to control emissions. If it can't burn everything that's being given to it, then it will cut back.

I'd say that #1 is the more likely culprit. The lazier the torque convertor, the worse it will respond to huge bursts of power.
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My 95 525i behaves the same way. Every 2.5 liter that I've driven with an automatic behaves this way.

Especially with the A/C on. The engine just doesn't have enough power.
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