Backpressure problem? - BMW Forum

Zuwinken · 05-25-2007, 09:32 PM

I just bought a '89 325i and it has a couple of major problems. First off I think there is a backpressure problem because it has no muffler nor a cat. just straight pipe off the manifolds. I have almost no power at all and it cuts out at take off but then catches half a second later. I checked the timing and the wires and it is all in order. The plugs a little worse for wear but they're fine for now.
Next up would be the a similar problem I read earlier that the fuel gauge sits at full and then jumps around when you turn or just whenever and then goes back to full. I have no idea how much gas is actually in there.
Lastly odometer does not work at all. I have a buddy who has a '91 audi 100 quattro and they have a little wire solder in the back of the dash and I was wondering if perhaps these cars have something similar.
I have never owned an import car before and any help would be greatly appreciated! I dont want to get rid of this car because it is very excellent condition other than these problems!

Thanks
ZUW

Starmavin · 05-25-2007, 10:41 PM

Back pressure isn't the problem. Check your intake boot for tears, also test your throttle position switch and coolant temp sensor. Make sure all the filters are good. Your fuel gauge problem is the sending unit found under the passenger side of the back seat in the access panel, four screws and four nuts and it's out. The odometer not working is due to deteriorated drive gears in the cluster (very common), you can buy a set and replace them.

Zuwinken · 06-01-2007, 08:25 AM

Thanks! I really appreciate the help, I'll be checking those shortly

Zuwinken · 06-01-2007, 11:55 AM

ok i checked everything and the intake boots looked ok. I changed out all the plugs and they all were fouled with a sizable amount of oil on them. Is it possible the rings went bad? It seemed to run fine, no more shaking and the response was good. If you punch it and want to run at high rpm it starts to go up and down in the rpm like it wants to cut out but it catches before it can. Any ideas?

Starmavin · 06-01-2007, 05:43 PM

Where the oil on the plugs is coming from depends on your answer to this question: Does your car put out blue smoke when you first start it after sitting over night and stop, or does it put out blue smoke all the time?

Check your throttle position switch again, if it's good, spray WD40 or liquid wrench in the idle control motor to clean it out. Also clean your throttle valve.

Zuwinken · 06-02-2007, 08:45 AM

it has no exhaust system on it. It only has a little bit of straight pipe coming off of the manifolds. I can't get a good look at it. I'll see if maybe I can get a neighbor to check it out for me. I've never seen any smoke while driving so I assume that it would just be at start up if any.