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Sluggish Performance!!

Discussion in 'E30 (1984-1993)' started by cj morgan, Mar 25, 2008.

    cj morgan guest

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    My bimmer just doesnt seem to have the power that it should. it's rated at 168hp but i drove a 2007 Nissan Sentra rated at 140 horses and it seemed to have a lot more get up and go all around. i dont know what the problem is other than it is a '90 and i guess cars get slower as they get older. does anyone have any suggestions to get my car up to par?
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    mjweimer

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    I would start with a basic tune up. Valve adjustment, spark plugs, distributor cap and rotor and maybe an oxygen sensor is where I would start.

    How many miles are currently on the car?

    If performance is still sluggish after doing a tune up then a check of the fuel pressure would be next on my list. My last 325iS had a bad fuel pressure regulator and replacing that brought back the smoothness and torque one would expect from a BMW 6 cylinder.

    Matt

    cj morgan guest

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    right now it has almost 172,000. i believe the oxygen sensor was replaced at 120,000. new spark plugs at 165,000. i'm not sure of any other recent tune-up work done to the car other than that. i was told the spark plug wires may need to be replaced, but thats about all i know.
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    mjweimer

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    It is possible at that mileage that the spark plug wires would need replaced but they are expensive and may gain you nothing. Have you been detecting any sort of mis-fire?

    When I had several higher mileage E30's I kept a spare plug wire (sourced from a junkyard - #6 cylinder) for troubleshooting bad wires. I simply, one at a time, removed each end of the wire and replaced it with the spare working my way from front to back. It helped me find a bad wire on my (now sold) '88 325iS.

    At this point, I would check the distributor cap and rotor and test fuel pressure.

    Matt

    jmalter guest

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    That I did at one point have to replace my spark-plug wire harness, as it had aged/deteriorated to where there it had gaps inside its insulation.

    Another thing, could be dirty/sticking fuel-injectors, especially if the car's been inactive for awhile. You could add a bottle of cleaner (something called 'Techron' IIRC?) to your next fill-up & run through that tank-full, deferring your opinion until you've moved that cleaner thru your motor.

    missmelyssa guest

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    I believe my car sat a while before I bought it. (poor thing)
    Right now I put 91 octane and Lucas fuel injector cleaner (lasts 2 tanks).
    I'm on my 2nd tank.
    This is my first e30 so I have nothing to compare it to, but it does seem like it doesn't have umph due to cars passing me. (and I've always driven 5spds)
    Plugs, air filter, and oil and filter were replaced.
    Other items will be replaced soon...awaiting their arrival.
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    89dle30

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    Once the tune-up items are covered, one other area that can affect perceived performance is the throttle response and proper cable adjustment. The cables do stretch over time. I seem to remember reports on the old bmwe30.net forums of actual performance issues because the cable was stretched enough to not trigger the WOT mapping at the Throttle Position Switch even when hitting the pedal stop. Not that you'd be at WOT typically while cruising on the highway...but maybe around town pending driving style.

    I think the spec for the adjustment is in the Bentley. You don't want to overtighten, prop the throttle open too far, and fail to trigger idle properly at the TPS at the other end of the range.

    On my last e30 purchase, adjusting the cable was one of the first "fixes" I did, and taking up the slack made a significant difference in throttle response and overall driveability, especially for rev matching downshifts. I suppose you can get used to the slack and compensate, but I was going between 2 e30s at that time, and my older car had the cable just right, so the newer one felt sluggish in comparison. Checking the AFM for proper operation can also help if fuel delivery and spark are OK...

    Cheers,
    Pat
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    Brian A

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    Your stock ECU can't exploit better detonation characteristics of 91 octane gasoline. It does no harm but provides no benefit.

    You can reprogram the car to use 91 octane fuel by replacing the fuel table chip. That gives a nice cheap HP boost. Tuners such as Dinan & Turner/Comforti make them. Personally, I like the Dinan chips (I get crawled over every time I say that) since Dinan is a California tuner and I feel better about passing California Smog tests.

    I found the torque & hp vs RPM curves that Dinan used to publish for their E30 325i chip. They show a maximum increase in torque of 15 ft-lbs at 5000 rpm above the stock chip. Maximum hp is increased to 177 hp at 5750 rpm.

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