Stall/Poor fuel efficiency mileage issue - how would you diagnose?

[smhapp]

All,

I just replaced the vacuum hose from the check valve to the back of the engine. Have had really poor mpg for a while. Could the hose have contributed or is it likely something else?

Car stalled on me going a slow speed last night; first time that has happened. Turned on just fine again. How would you diagnose? Looks like the fuel filter was replaced 7 years ago but the car has only put on 23K in mileage since then. I replaced the evaporator purge valve several months ago.

Thanks in advance, guys!

S

[Leothelion092]

Has the fuel pump ever been replaced? If not I'd give it a test before doing anything else. Fuel pumps almost always go out at this age for an E46 that hasn't had one replaced

[Honolulu]

I'd diagnose this one like I'd diagnose every other problem on a OBD-II car... READ THE CODES AND DO A LITTLE RESEARCH ABOUT WHAT THEY TELL YOU.

over and out.

[smhapp]

Nope. Fuel pump hasn't ever been replaced. Good suggestion

unfortunately or or maybe fortunately I don't have any codes.

Thanks

[MarcoZandrini]

What scanning tool did you use to scan the engine computer (DME in BMWeze)? Did you scan the automatic tranny computer (EGS). There's a fuel pressure test valve on the fuel rail. Item #7 is the cap to the fuel pressure test valve. Fuel pressure has to be at least 50psi at all engine speeds.

http://www.realoem.com/bmw/enUS/show...diagId=13_0900

[Leothelion092]

It's really not that hard to get access to the fuel pump and it should really be replaced if it never has been, even if that's not what it is you'll have the peace of mind of another 100k+ miles and at LEAST another 5 years before it fails. It's easy, it's not too expensive, and it gives you peace of mind

[smhapp]

I have the Peake tool so no I did not scan the engine computer. Car is a manual. I know where that valve is... thanks for the link i will take a look.

[MarcoZandrini]

The Peale tool actually does a good job of giving you specific info related to the problem. Scan the engine computer (DME).

[smhapp]

Agree -- need to do the fuel pump. I watched enough DIY on this that i feel pretty confident except for getting that metal ring off. When I hammer, bad stuff happens.

[smhapp]

Dumb question but how do you scan the DME? Do i need to take to an Indy shop?

[Junglenut]

A simple OBD 2 code reader should be best for getting the answers to engine running problems.

[Honolulu]

I've done the fuel pump plus filter (integral) replacement and it's not difficult. Have a good look at the short hoses down there, I changed mine proactively because I had the proper hose already.

OTOH I would not (now) buy and change a fuel pump without getting fuel pressure tested. But the occasional no-start problem my daughter was having, went away completely after the pump change. I count it as a success.

[Eaglesail]

Curious.........but have you ever dumped a can of 'fuel injection cleaner' into a full tank of gas?

I use 'SEAFOAM' I buy at Wal*Mart!

It really-really-really works...if this is your fuel problem...as is more often than not....try it, then report back.

It may take more than one application...but you should see improvement upon the first..I did it 3 times before seeing my smooth running m54. Try this first.

[MIKYZZ4]

Perform a scan using the Peake tool and associated cable, connecting to the diagnostic port.