90 bmw 525 runs sluggish

[troysmith]

i have a 1990 bmw 525i automatic with 200,000 miles but is in great shape.. no smoke or burning oil but seems to be sluggish. it accually surges and i can watch the vacuum gauge move up and down and im certian something is holding the power back..my wife drives it but i just noticed it any help woud be apriecated..

[sidewinder69]

Open the hood with the engine on and listen for whistling sounds around all rubber piping (for air leaks), if you find one put electrical tape over it. Or replace the pipe.

Also check your intake from air filter back and make sure that it is all connected snugly and also that any gear clamps are tightened down. Check your air filter too...it might be dirty, or full of dog hair or something like that.

If it isn't any of those things do the stomp test and check the codes.

Link:

http://www.bmwe34.net/e34main/trouble/engine_codes.htm

[troysmith]

thanks but it seems there is no leak ..ive replaced the plugs, fuel filter, and cap and rotor with no change.ive tried the stomp test with no results seems maybe im doing it wrong..any more ideas..

[sidewinder69]

I hate to say it but...plug wires? Hell, try some fuel injector cleaner as well.

My 535I was doing the surge thing as well, I put new plugs in it. Also the elbow right after the intake filter was cracked so that wasn't helping either.

I replaced that, threw some fuel injector cleaner in...and took a 10,000 km road trip. HA! I don't recommend that last part...but I don't have a surge now.

If you can hear a lot of back pressure you might just have some cat material broken and turned sideways in your exhaust. Had that problem in my old '85 Toyota Corolla GT-S. HACHI ROKU BABY!!!

Back pressure and 7000 RPM DON'T MIX!!!!

If when you kick it down and it goes, then slows up, then goes and slows up again it could be a fuel pump....sorry.

One last thing, if you only have that problem when it first starts up...or when it's cold...it's an old car. That's character.

[troysmith]

ok thanks.. by the way it does it when is warm to it seems to be surging about 3000 up slowly making its way to redline but struggling.. any info on testing the cat or fuelpump??

[sidewinder69]

With the cat try shaking the exhaust pipe....when cold obviously. Sorry I had to put it just in case.

If you hear any rattling inside the exhaust then you know some cat material is broken inside.

You put any fuel injector cleaner in? I keep saying it but you haven't said if you've done it. It does work.

BTW I just thought of this. Do you use premium fuel? It is kinda dumb but the wife might be trying to save you some money...or just goofed. You'll know if you hear the dreaded PING!!!!

Check the voltage with an ammeter with the fuel pump under load from the engine. I.E. revving the engine up slowly. I don't know the baseline reading though sorry.