O2 sensor heater...what can affect it?

[boyd_dave]

If the IAT is faulty and telling the ecu the air is hot, would it cause a lean fuel condition?

Otherwise, my first guesses are vacuum leak, fuel filter, fuel pump, injectors, o2 sensor...but it sounds like you covered most of those.

[trackjunkie21]

a lot of resistance in a circuit, but which one

[Beej '86 325es]

I checked my harness some more and read about the E34/E36 differences. Now I'm certain I have an E36 harness. So I'm not as concerned about bad wires now.

So I guess I'm back to asking myself what the fundamental issue is:
What would cause a lean condition at idle for 9 minutes, then suddenly it's fine? Not a bouncy idle, just lean and rough.

[Beej '86 325es]

where is your o2 sensor mounted in the exhaust/header? I had alot of trouble with 02 heater 1264 code for a long time. the ultimate fix was to move the o2 sensor alot closer to the engine. if its too far away, it will not work properly.

Mine's mounted in the header.

Maybe this'll help
http://www.r3vlimited.com/board/show...highlight=idle

Already tried that.

[trackjunkie21]

I seem to have solved my problem, it is infact exactly what Boyd_dave has said. Moving the 02 closer is a must, aswell as fixing any exhaust leak you have before the 02 sensor, they really mess with a lot of things.

[boyd_dave]

where is your o2 sensor mounted in the exhaust/header? I had alot of trouble with 02 heater 1264 code for a long time. the ultimate fix was to move the o2 sensor alot closer to the engine. if its too far away, it will not work properly.

[nando]

does the intake air temp sensor even affect anything? ..

Is the pope from germany..

[Fusion]

Maybe this'll help

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

[Beej '86 325es]

does the intake air temp sensor even affect anything? ..

It shares an ECU ground with the TPS and CTS, but I'm focusing my efforts on the CTS and O2 wiring for now.
It'll be Monday-Tuesday before I get back to it though.

[lolcantturn]

does the intake air temp sensor even affect anything? ..

[Beej '86 325es]

I inspected my harness, all that I could without completely tearing apart the engine bay. I couldn't find any signs of bad wires; all clean.

I realized I hadn't checked the air temp sensor yet, on account of how much of a pain in the ass it is to get to under the manifold. I checked resistance on the sensor and it looked ok.

[lolcantturn]

[lolcantturn]

Ok so I've been looking through an E36 ETM at the 88pinout diagram..
I'm not an expert on wiring AT ALL but

It seems the wire that are burnt in that photo are the exact brown and green wires that go to the O2 sensor. They come off the O2 sensor in that four wire pack (Yellow, Black, Brown, Green, the four colors of the O2 sensor), and almost go to the ECU, but get rerouted back to the relay (which I think is weird). However the yellow and black go to the DME as pin 70 and 71- O2 heater
BUT, there is one strange thick clear wire that also comes off that four wire pack, and splits into the camshaft position sensor Pin 16 and 44 on the ECU

http://www.bmwtechinfo.com/etm/data/e36/e36_92.pdf

Thats the ETM

I'm not trying to hijack your thread, but it seems like we are having the same issues after all.

[lolcantturn]

Let us know how looking through the ECU wires go..

[Beej '86 325es]

Bad grounds can cause a million issues that are hard to track down. It seems like 50% of engine swap problems I read about are bad ground related. That burnt wire looks bad dude! :) I'd remove that wire and re-run it...maybe using a slightly thicker gauge wire. Continuity doesn't always mean it's good. Logically, it might seem like it is ok, but it could be a weak connection....which is bad for grounds.

I'm pulling off my harness connector at the ECU tomorrow to inspect.