Fuel Level, Idle and load problems

[SpidersWeb 0]

Hey everyone,

This 535 I've picked up has a whole pile of problems, most of which I know what needs doing, except for a few that I could really use some advice. I've recently moved from doing up Mitsubishi Starions, which I knew inside out, and now the BMW I know nothing about, so any advice, tips, or anything you can add would be most appreciated Ok so there are three main problems that I dont know what to do with:

First of all, the idle 'hunts' a little, the previous owner told me this was due to the big bore exhaust he had fitted. I love the sound but I'd prefer my BMW idled like a BMW should. Is this the case, or is there something more sinister at play? Any tips?

Second, if I'm cruising along the motorway at 100 @ 2000rpm in Economy, and I start to gently accelerate the car starts surging a little, the harder I try to accelerate the more it does it until it down changes or I flick the Sport switch and make it down change. This problem seems to happen only at higher speeds, and only between 2000 and 3000rpm.

Third, the fuel gauge is wack. We filled it to the top after I bought the car, and after paying for the fuel and having a little cry at the price of gas, I headed back home. When the gauge read half-a-tank, we refilled and sure enough the gauge was 100% accurate. Once we got the car back down here there was just under half a tank left. Then as the fuel level got a little lower (and I mean a little, as in <20km driving) the car started saying '1/4 tank' and after warming up would move to say just under 1/2 again. Then today it was like 'lol no gas' with fuel light on and definately on R. While cruising at 50KPH, it changed its mind and said 'quater of a tank' then a few seconds later went back to 'lol no gas'. I'm guessing this is the sender unit at fault, and I'm wondering if anybody has any advice or tips on what to do here?

(The previous owner did say the fuel gauge was dodgy, and gave me a petrol can with the car)

I'll be doing the alternator belt, brake pads, oil, oil filter, fuel filter, car stereo, OBC wiring, spark plugs, and fix the door locks before these problems, but would love any tips, advice or your own experiences!

Thanks heaps

[ducatiss 1]

First up congrats on buying a BMW - challenges plenty but they are still a relatively simple engine to muck around with and with a workshop manual, you should be able to accomplish most things with common sense.

Re the surging - check all your air hose connections - check the clips, and the hoses for leaks as this is the no 1 cause of wierd idles issues. Then check the fuel pressure regulator, idle valve and then the fuel pump. Fuel gauges do get dodgy usually due to bad connections at either the guage itself or the actual fuel sender. Either can cause what you are describing.

[jochen 4]

Check also the re-chargable battery in the instrument cluster. This serves to maintain the odometer memory when the power is off, but when the battery gets old all sorts of wierd instrument gauge problems occur.

If in doubt change it, they only cost a few bucks from Jaycar.

Instructions to do so are all over the 'net

Jochen

[SpidersWeb 0]

Thanks heaps to everyone who replied.

There is definately problems behind the intstrument cluster, as the TRIP and CC buttons do not work, and a couple of the illumination bulbs are out, not to mention the whole fuel gauage problem. So that will be my first port of call with that problem.

On Saturday I got the central locking working, and on Sunday I blew the auto transmission with a touch of overheating just for fun. Clearly its going to be one of 'those' cars. I haven't investigated the auto yet, but I'll make another post, see if anybody has any ideas. Wont have it on jack stands until Saturday. So if anybody saw a black 535i getting towed over the haywards, that was mine its got half a tank of gas too

Hope everyone else out there had a better weekend!