Johan Axelson
11-28-2010, 02:01 PM
Hi all, I have a problem with my oxygen sensor. I think?
I have one of these:
http://img831.imageshack.us/img831/6528/p1010762f.jpg
with one of these
http://img831.imageshack.us/img831/9340/p1010761z.jpg
The engine is from a Euro 535 -91 (I live in Switzerland) and is installed with the proper ECU and a Oxygen sensor / lambda sond but no cat.
It has been running quite well for several years but lately I have been having some issues.
It is not running 100% and feels weak. I am not 100% sure about gas consumption since the trip meter is not all that exact.
I have just now replaced the oxygen sensor and the temperature sending unit. The blue one that is towards the middle of the engine. No change.
When I measure the output signals from the O2 sensor where it comes into the engine it bounces between appr. .2 and .8V which is what I understand is correct from what I have read here and while googling.
This is when idling and revving up and down.
That of course does not mean the ECU gets that information.
I have looked for vacuum leaks but cannot find any.
If I reset the ECU, i.e. turn off its power overnight the car is very strong and runs well in the morning until it gets warm(ish). This is where I thought the temperature sender might have been acting up. Since I get heat inside the coupe I think the thermostat opens properly. But maybe too early?
I managed to get a shop look at the error codes in the ECU and it said O2 sensor error. Which is odd since it seems to work but signal does maybe not go to ECU and puts it in "limp home" mode.
I do not have the analysis equipment myself so I cannot test as well as I would like to. I would need a tester over a few days to see any sort of pattern letting it run warm and cold and test while running to see what happens.
Since the car can run well I guess the AFM is OK. And as far as I understand O2, AFM and temperature are the main sensors?
This thread seems to say that : http://forums.bimmerforums.com/forum/showthread.php?t=1562989 Very good read.
Also as it can run well I also assume injectors, fuels system etc are OK.
So question 1, is there anywhere to read what the oxygen sensor has told the ECU? I tried the two big round diagnostics but could not find a similar signal. I could of course splice into a cable..
Question 2, can I soemhow see if it is in "limp home" mode?
Question 3, do I actually need the lambda with this setup? I.e. no cat. Some say I don't but I cannot imagine how that would work.
Any tips of things to check and measure would be greatly appreciated.
I should say I am no whiz with this and am learning as I go so please be patient with dumb questions.
Oh and on a sideote, when a shop connects to the ECU they often have to choose Motronic 1.1 to make it work. I thought this was 1.3. Odd...
Rgds,
Johan
I have one of these:
http://img831.imageshack.us/img831/6528/p1010762f.jpg
with one of these
http://img831.imageshack.us/img831/9340/p1010761z.jpg
The engine is from a Euro 535 -91 (I live in Switzerland) and is installed with the proper ECU and a Oxygen sensor / lambda sond but no cat.
It has been running quite well for several years but lately I have been having some issues.
It is not running 100% and feels weak. I am not 100% sure about gas consumption since the trip meter is not all that exact.
I have just now replaced the oxygen sensor and the temperature sending unit. The blue one that is towards the middle of the engine. No change.
When I measure the output signals from the O2 sensor where it comes into the engine it bounces between appr. .2 and .8V which is what I understand is correct from what I have read here and while googling.
This is when idling and revving up and down.
That of course does not mean the ECU gets that information.
I have looked for vacuum leaks but cannot find any.
If I reset the ECU, i.e. turn off its power overnight the car is very strong and runs well in the morning until it gets warm(ish). This is where I thought the temperature sender might have been acting up. Since I get heat inside the coupe I think the thermostat opens properly. But maybe too early?
I managed to get a shop look at the error codes in the ECU and it said O2 sensor error. Which is odd since it seems to work but signal does maybe not go to ECU and puts it in "limp home" mode.
I do not have the analysis equipment myself so I cannot test as well as I would like to. I would need a tester over a few days to see any sort of pattern letting it run warm and cold and test while running to see what happens.
Since the car can run well I guess the AFM is OK. And as far as I understand O2, AFM and temperature are the main sensors?
This thread seems to say that : http://forums.bimmerforums.com/forum/showthread.php?t=1562989 Very good read.
Also as it can run well I also assume injectors, fuels system etc are OK.
So question 1, is there anywhere to read what the oxygen sensor has told the ECU? I tried the two big round diagnostics but could not find a similar signal. I could of course splice into a cable..
Question 2, can I soemhow see if it is in "limp home" mode?
Question 3, do I actually need the lambda with this setup? I.e. no cat. Some say I don't but I cannot imagine how that would work.
Any tips of things to check and measure would be greatly appreciated.
I should say I am no whiz with this and am learning as I go so please be patient with dumb questions.
Oh and on a sideote, when a shop connects to the ECU they often have to choose Motronic 1.1 to make it work. I thought this was 1.3. Odd...
Rgds,
Johan