Uh-oh..wifey calls...rough running and CEL...

[billb]

... back to your earlier post re. the MAF: Do you have access to a spare one to swap out for a trial?? False air mass readings to the motronic will do many things - like richen the mixture which will cause a "red-herring" error code on the O2 sensor.
Anyway, it is possibly one of the MAF failure modes.

I've emailed our good friend Mr. Bill R...hoping he'll have the magic "AHA" fix...

Thanks!

[ryan roopnarine]

have you tried sniffing the exhaust with it running to see if any gas is gettting shot out unburned?

[billb]

have you tried sniffing the exhaust with it running to see if any gas is gettting shot out unburned?

I'll pull a plug or two tonight and take a look. Will also check voltage on the O2 sensor to see if it's sensing lean or rich. Of course, with the CEL on full, I'm guessing it's going to go full rich for safety.

Thanks for continuing the discussion!

[ryan roopnarine]

perhaps this will be helpful if you haven't seen it already

http://bmwe32.student.utwente.nl/sea...leshooting.htm

[ryan roopnarine]

if the cel is on constantly, but you have a normalized idle, it could be that the computer just adjusted to the problem and will try to substitute an idle speed conducive to it running somewhat properly. i'd unplug the battery and see what it does sans memory and see what problem is being covered up.

ps. i only say this because i know it from experience. if the ICV hose is kinked, the car will adapt a high idle (but steady and seemingly normal) of about 800-900-1000 rpm after about 30 mins or so of runtime. it could have adapted to whatever problem you have.

[billb]

ECT sensor checks okay. There was oil in the sensor cavity, maybe shorting out the connector. Removed, replaced with known clean good one from my E30 (same part number), and cleaned connector. No better.
Replaced FPR vacuum hose-old one looked okay, but as a matter of course...
All, and I repeat, all vacuum hoses look good, including fittings.
Valve cover gasket was recently replaced 500 miles ago, and is still sealing well.
Oil cap secure, fuel cap secure.
Charcoal canister lines look good.
Replaced o-ring on crankcase ventilation fitting at valve cover, good snug fit now.

Disconnected battery, clearing codes (1444), then repeated the earlier starting exercise. It starts smartly, runs for a few minutes, then the idle gradually becomes more unstable, until, after about 15-30 seconds, it oscillates wildly, from low 100's up to 1500 or so, about 2-3 times, then dies, running rich when it dies.

This one's got me stumped. Oh, and it hasn't thrown a code again yet...

[ryan roopnarine]

check engine service will not store codes in my car unless it is driven or runs for a very long time. you saying that it stalls out before a minute or so? i'd nurse it to high idle and try to drive it around your neighborhood and see what number it comes back with. fwiw, my friend's acura 3.2 had a bad oxygen sensor (s in his case) and it would cause his idle to do what you describe of it in your latest post (although it wouldn't stall). don't know if the same could be applicable here, i have a hard time believing that the car wouldn't have a drivable idle with a dying oxygen sensor (albeit with a drop in mpg).

[billb]

did some more snooping. Checked all coils...good. Checked all coil connectors to plugs...1.8kOhms...+/-0.1kOhm...good. Checked plugs, all fouled and black, suggesting all six cylinders are rich, kind of ruling out a stuck injector. Checked all relays in E-box...good when applying 12V, they make the appropriate circuit (tested with 9V battery). Checked old O2 sensor...hooked 9V battery up to heater circuit, then held sensor over propane torch. It is going back and forth around 0.7V rapidly according to how I hold it in the flame...good. So, the O2 sensor may be good. I managed to get it out without dropping the exhaust, so I may put it back in instead of using up my new one when I get the intake gaskets installed and idle hose connector installed. Checked every hose, including those at the gas tank expansion tank...all good. Last steps are MAF and ECU...yuck...

Will keep you all posted...I'm sure you're on the edge of your seat.

[Geoff Hoad]

That's ok, Jr's got another four in his is!

[billb]

It'll actually be cheaper for me to install a new FPR than to buy fuel pressure gauge...hmmmm...lots of history on stuck FPR causing rich conditions. Let's try that route, since all the sensors check out A-OK...