O2 sensor heater...what can affect it?

[Beej '86 325es]

like this

http://www.r3vlimited.com/board/showthread.php?t=192533&highlight=backfeed

[Beej '86 325es]

HD Video of relay clicking on after 8-9 minutes

So for some reason the relay isn't clicking on until about 8-9 minutes. I've tested this 3 times on cold and warm starts with the same result.

I got to play with iMovie a bit and make an HD video of the problem. :)

http://www.youtube.com/watch?v=WjvLuaXvGH0

[Beej '86 325es]

Tested with C101 pin 6 disconnected from x20 pin 22. Same result. 8-9 minutes until it clicks on. Lost power to the diagnostic port.

Reconnected pin 6 and swapped DMEs. Same result. 8-9 minutes until it clicks on.

O.M.G. I have no idea what else to check.
It seems like it's got to be something not with wiring, but with the logic. Something is telling it to wait to click on.

Would there be any harm in installing a jumper in place of the relay? I guess I don't understand the purpose of it if it's always supposed to be on anyway.

[nando]

I'm stumped!

a better idea would bet to run a jumper from pin 85 of the FP relay to pin 85 of the O2 relay. then the FP signal would turn on both (this is safe, I've had mine wired like this for ages). Of course remove the connection to pin 85 of the O2 relay from the ECU.

[Beej '86 325es]

That's not a bad idea! I've been researching time delay relays, but this is much simpler.

Out of curiousity, why do you have yours wired this way?

Thanks!

[nando]

because my ECU doesn't have an O2 activate pin - MS3. I think a lot of people are using the (terrible) Megasquirt relay board to power their widebands, or some other equally painful way. Why reinvent the wheel when BMW engineers have done all the work for me. :)

[328ijunkie]

The ECU is supposed to control the O2 sensor relay from what i can see
If Pin 38 is not making its way to pin 85 of the relay then thats where your issue lies.
Power for the relay on both sides is provided by the Main/ECU relay.

[Beej '86 325es]

The ECU is supposed to control the O2 sensor relay from what i can see
If Pin 38 is not making its way to pin 85 of the relay then thats where your issue lies.
Power for the relay on both sides is provided by the Main/ECU relay.

Correct. I've checked continuity on every relay and sensor and all checks out. Something is telling the ECU to make a very clear "switch" between 8:45 and 9:00 after starting. Unfortunately I don't know (and doubt anyone on the forum does) what the innerworkings of the ECU logic. I'm sure other sensor(s) are involved though.

[trackjunkie21]

Have you swapped in a good working DME?

[328ijunkie]

+1 as I mentioned I've never had this issue....

[Beej '86 325es]

Have you swapped in a good working DME?

twice...and different chips.

I'm going to go ahead and do what nando suggested. Lately I've been replacing stuff just to replace stuff. The last thing I can do is rip out the whole wire harness and start from scratch...but sadly, I don't even think that would fix the problem.

The other day I saw a photo of an E34 M50 wire harness. I thought I had an 325 harness, but now I'm not sure. The reason I'm wondering is because the O2 portion of the harness is routed on the driver's side of the engine block. It's like I had to route it backwards to get it to the O2 sensor. I wonder if there's a difference there.

[trackjunkie21]

I'm starting to think there may be something in the actual wiring from the computer to the relay, but I would try Nando's suggestion, seems like it may work.

[M-technik-3]

funny you should say that... the story goes that at first when I finished the swap, it idled at like 1,100rpm. ICV was seized, open. I had actually not touched the idle screw, but my old TB didn't ever close on its own to rest on the throttle stop. I could (barefoot) pull the pedal and bring the rpms down. I tried playing with the throttle screw, and I thought I had a nice spot of not-too-much-vibration and not too high revs where the throttle did come back to the stop, but that got me where I am now, and it does the weird warm up sequence. I am swapping a used TB/TPS tomorrow (I hope) and will see what happens. I'm not sure if my O2 sensor is damaged, but I do know that the preheat works. When I initially got the car running, without exhaust, I was a dumbass and had the sensor hooked up leaving the plastic protector cap on the sensing end... and the cap melted. It came off the sensing end cleanly, but I'm now questioning if harm was done.

OFF Topic: Having two different discussions will make this thread convoluted. You have a thread relating to your idle issue correct? Maybe It needs a bump.

[Beej '86 325es]

Jumped relay installed, check out my relay now! (below) The O2 sensor has voltage as soon as I start it now.

...But guess what...

It still runs very lean when the engine is cold. I wonder if the O2 isn't meant to turn on until after that long of a period. I'm going to evaluate some more, as I didn't time it tonight. But it behaved exactly as it did before...lean for 5-10 minutes then suddenly the A/F ratio clicks down to a normal level and idle improves. It appears the O2 heat isn't what's causing the issue.

[nando]

no - the heater must work right away! the O2 sensor doesn't give appropriate readings until it's warm. that's why they have heaters. for emissions reasons, they're basically always active, even if the O2 input isn't being used.

your lean condition could be caused by something else. vac leaks? MAF cars are sensitive to those..