ECU & misfire problem

[MCDONNMJ]

Hi, Does anybody have a suggestion for a problem that I have on a '97 328i Cabriolet (E36, M52 engine).
After the car warms up I get a single misfire and the ECU seems to switch to "safe mode" resulting in the engine running as though it is choked. It does not misfire again until as follows, it is reset.
The problem is easily reset by turning the iginition off, starting the engine and driving normally. It will then midfire and return to "choked mode".

I have replace both lambda sensors (front) but cannot finda any post cat sensors as described for post '96 cars. I'm sure that it is OBDII as I cannot get the codes to work from the accelerator method.

Any suggestions would be accepted with regards the problem and also why the system does not seem to comply with the OBD change at or around '96.

Martin :(

[ElSupremo]

It would definately be OBD-II after '95, unless someone converted it to OBD-I.
With OBD-II you should have two O2 sensors in the exhaust manifolds, and two post-cat.
I'd get the codes pulled, and I'd also recommend testing your coil packs to see if you've got one that's gone bad on you.

[MCDONNMJ]

Thanks for coming in so quickly.

I've been under the car determined to identify post cat sensors but could find no sensors, sockets, wires or anything that suggested that they'd ever been there. The exhaust has a bridging pipe between left and right, between the small silencer and cat. Is this correct for the later models do you know?

I have been unable to find an OBD plug under the dash as described in several publications and info on the web again pointing for this to be OBDI.

The car is correct in terms of all documentation so I'm confused.

Thanks

Martin

[ElSupremo]

Here's a diagram of your exhaust sytem: http://www.realoem.com/bmw/showparts.do?model=BK83&mospid=47477&btnr=18_0253&hg=18&fg=10

http://www.realoem.com/bmw/diagrams/g/a/191.png

It only shows one O2 sensor, but it shows 2 bungs.

The OBD plug is in your engine bay. Here's an article that shows where the plug is, and what it looks like: http://www.pelicanparts.com/bmw/techarticles/E36-Service_Lamp/E30-Service_Lamp.htm

[anisamy2]

What is OBD-II? I have never heard of it.

[Mark at Quarry motors]

it depends what country you are in some versions will have post cat lambdas and some dont
you need to get a diagnostic scan done this problem usually occurs when the e.c.u has reached a fuelling control limit and cannot richen or lean off the fuel mixture any further this can be caused by a number of things such as air leaks ,air flow meter problems ect.