Driveability Problems '94 530i

[schilke]

I am helping out a friend with a '94 530i whose car seems to be running in some kind of limp home mode. No power, but enough to barely get around.

I have a peake tool, and pulled the codes several times, reset them, pulled them again. It pulled both O2 sensor codes every time.

Changed 02 sensors. Still runs the same. Haven't pulled the new codes yet, but can bet they are the same.

THis weekend, we will check for intake leaks, but other than that what should I check?

Will a shitty DME cause this condition too? And how do I know if it's the DME or not? Can I test it?

Thanks all!! Don't know much about BMW v-8's...

[billB]

Schilke

When you pulled the codes for the O2 sensors what exactly the code reads? let me know. What I am getting at is to pin point if its a control limit on the O2 sensor or it is O2 sensor itself going south!!
billb

[schilke]

Bill B,

Nice to hear from you!

I will get the actual wording from the booklet after lunch, but if I remember, it says, "Oxygen Sensor #1" and "Oxygen Sensor #2." I don't remember anything about limits.

Its Table K11, code 0c and 0d I think in the Peake book. You have a Peake book don't you?

Mine's in my car and I'll get it later.

Thanks for your help.

[billB]

Schilke: pleasure to hear from you again

I am at work now and you may have something like PRE and /or POST Cat O2 with number. In this case I'll check the connection in the plastic box 1st (unlikely though) the plastic connectors for the the pre ones sit on top of engine under the plastic cover where it say BMW on the engine.
When I get CONTROL LIMIT on a particular sensor you know it is overwhelmed trying so hard to compensate for another problem. i.e too lean vs. too rich type of a deal.

good luck

Bill

[schilke]

Billb This engine only has 2 O2 sensors, pre cat, down under the car.

I had thought about checking the continuity of the harness from the sensors to the 'brain' but wasn't sure where the brain is. I'll try to trace it this weekend.

Even then, I don't think my multimeter has long enough leads!

Thanks for the reply.

[billB]

The 1994 530I has Two - OE Type Before Catalyst; I have seen them for about $88 each. However my 1997 528I has 4 of them; 2 precat. 2 post cats
regards
billb

[schilke]

Any reason that un plugging the MAF would cause the car to run slightly better? Does the car go into any particular limp mode when the MAF is fouled?

[billB]

Yes and the effect of unplugging the MAF causes miscalculations with the volumetric efficiency of the engine and the calculations programmed into the ECM. Someone with more expertise may be able to tell us more. but I trust you get the idea that eventually you will cause a MIScalculation and/or error and hence a check engine light fault pointing at your MAF.
Billb

[schilke]

Not that many will care, but after replacing 2 O2 sensors, and a $165 diagnostic from the dealer, it turns out that the problem was in the fuel delivery system.

Fuel pump and both fuel filters were changed out. Car runs fine now.

Imagine that? A faulty fuel pump will cause hesitation, but pull 02 codes??

All you 3.0 v-8's might need to remember that one!