Loss of power

[eduardope]

I have a 1998 328i with about 85,000 miles on it. I have been pretty good about oil changes and run castrol synthetic in it. I recently replaced the fuel filter as well as the spark plugs. Well, my girlfriend just bought a 1999 328is (e36). It wasn't until I drove her car that I realized how slow my car had gotten. I have noticed that my car didn't feel as quick as it used to but I just figured I got used to it. To confirm my suspicion I ran a zero-sixty side by side with my girlfriend driving her car and she was about 15% faster than me (she had 3-4 car lengths on me). Both cars are automatic transmission and hers has 55,000 miles on it. the only major difference is that I put 17" replica rims on my car with summer sport tires while hers has 15" with all-season radials. Could there be something wrong with my car or is the 328is really that much faster than the 328i? The only thing I could think of is maybe the timing (tensioner maybe??) as I have never had the car tuned up other than new plugs. Any ideas?

[Bengali86]

larger tires trun slower, slower off the line, but higher top speed, dont think it changes "Too much" but im not sure, I had 17s on my car, put back on the 16s for now. seems a bit faster than before off the line, also rim weight,

[Kevin325i]

The answer might be your wheels. How much do they weigh with tires? My stock 15 inchers with tires weigh 40 lbs.

Kevin

[El Presidente]

The best thing to do is take the car in for a compression test.

[TeeUp]

the 15% difference is i believe just a minimal cost for better looks that comes with the 17" wheels... if it were a something serious, i think your lag should have been more.

you're good with your ride, but checking your cars compression is not too bad either.

[328icoupe]

Is your fuel consumption normal? Another 328 owner experienced such a loss of power on another forum and he traced it down some cracked rubber hosing between the air filter and throttle body. 17" wheels came standard on a lot of 328is so it should not cause this 15% difference in performance.

Another thing to check is your idling and startup, are any of these rough? You might want to change the crankshaft and camshaft sensors.

Hope this helps. :wink

[chungaa1]

dude,
all u need is a simple tune up.
if u have a k&N air filter, u may try cleaning it and reoiling.
when was the last time u changed your spark plugs? i run 2 electrode with no issues. u should also pay attention to what viscosity of oil u use. try running 76 gasoline, 91-92 octane if u can, they have supposedly had the highest fuel sample ratings. u still have that big bulky spare tire in your trunk?? take it out, that thing weighs like 50lb... u want that roar sound, remove your baffle.. then u can pull up to M3 with confidence... haha
laters,
eric

[dutchbmw]

Originally posted by El Presidente@Jun 3 2004, 07:58 AM
The best thing to do is take the car in for a compression test.

Be sure there is enough oil in the carter. Less oil means warmer oil and that will increase the internal resistance.

I also agree with El Presidente!

[BlantonG13]

Could be possible that you just have some normal engine wear. depends on how you drive the car. Those size wheels shouldn't make that much of a difference because BMW stock rims are heavy themselves. 17s with 205/40s on them should be about the same overall size as the stock 205/60s on the 15s. Noticed any kind of leaks or anything? Might be something minute like a crack in a line or a little lost compression, lost vaccuum possibly. Have the dealer or someone run a tune-up. At 85k, sounds about a good time to get that taken care of.

-Mike

[BlantonG13]

Oh yeah, I noticed, more or less a question for the guys with all the knowledge....could the difference have something to do with one car being an IS and the other a regular I? One is a sport package, maybe some different engine, weight, luxury options???

[schnitzer328i]

Hey I've got a question...I'll probably get made fun of for asking this cuz it's probably really easy to find and a common term but what and where is my baffle? I've been trying to figure out ways to make my car sound better without spending money and this sounds cool so how do i do it? Thanks
~Schnitz

[007ben]

in the air box.

[dutchbmw]

Debaffle: http://www.bmw-forums.com/forum/topic12910.html

[Bengali86]

ive been told the IS weighs a bit less

my 325is (93) weighs less than my buddies 325i cabrio (95) (according to the stickers on the door jamb

[Kevin325i]

The "is" only weighs like 50lbs less than the 4 door, well atleast it is for the 325s.

Kevin