I purchased theAutotap OBDII to troubleshoot this CEL on 1997 850 GLT wagon and attached a read outhere (I spent too much already and I don't want to give it up yet)
I replaced a MAF and O2 sensor before Cat but not the one after Cat.
I am guessing it might be fuel injector is leaking because Long term feul trim ration is -7.8% (I learned it from one of website)
or something I missed here?
I check the vacuum hoses and all of connections and it looks good.
Do you have any idea on how to check fuel injectors
Thank you for yourhelp in advance.

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Is the Rear O2 sensor sweeping at all?

 

The Rear O2 sensor respond slower than front one according to AutoTap feedback
(I am guessing sensor 1 as front (before Cat) and Rear one as sensor 2 (after cat)
Rear O2 sensor is old.
Could you explain how control module respond from rear O2 sensors feedback.
Thanks again

 

The rear 02 sensor shouldn't sweep at the same rate like a front sensor does. It is for long term fuel trim, so the rear sensor could be faulty, but I don't have experience with these Auto Tap readings.

You really need to spend some time with several good cars to really get an idea as to what reading are normal. I've spend many hours with the Volvo Scan Tool and I came to realize that some readings are useful and some are plain useless.

I didn't see the code, what was it? Is it still present?

B

 

CEL code is P0172 (Long term fuel trim rich but only -7.9%) that I attached at my first message.
Comparing with other car read out is really a good idea
Thanks

 

Why don't you clean the rear O2 sensor and measure it again?

 

Cleaning O2 sensor is another good idea too
I will do it over the weekend andwill postthe resulthere
Thanks for all of your help

 

im getting the same code.. I cleaned the MAF sensor but it came back.. How do you clean the rear 02?

 

http://forums.bimmerforums.com/forum...d.php?t=324738

 

I found the culprit of CEL P0172 (Long Term fuel rich)
I have been working this one forabout 6 months on spare time (afew of hours per month) and replaceda MAF, an O2 sensor(front one) swapped old frontO2 sensor to rear after I modified wire lengths but it wassame CEL after a couple of drive.
I should listened"TECH"'s advice more seriouslywhen he recommend to check the vacuum line
Actually I spent a lot of timeforvacuum leak but Icouldn't find it until last week
Some mechanic mentioned to me to check the Thermostat, during theThermostat/Water Temp sensor investigation I noticed a vacuum line was hidden between power steering assy and intake manifold and was broken.This vacuum line was hard to reach without a lot of parts remove, so instead Ire-routed the end to other end with $3.00 vacuum line from Aut0Zone
Attached pictures for Ref
Thanks


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Glad you got it figured out.

 

I have the same problem hose. That hose goes from where to where? Thanks.