My AutoXray scanner keeps reading that he oxygen sensor is "NOT READY" and at the same time it tells me that I'm running in "OPEN LOOP". Even though, I get voltage reading from the oxygen sensor (via the scanner). Every so often a tap on the gas pedal will kick it into "CLOSED LOOP" and tell me the oxygen sensor is "READY". Typically pops back "OPEN" within a few seconds.

Will one cause the other to read this way (i.e. bad oxygen sensor keeps ECM in open loop)? Do I need to be looking somewhere else?

Other readings show the the system running "LEAN" most of the time.

 

Seems like a lazy 02 sensor...but is is normal at idle for it to fall under 450mv and stay...putting the the ECM into open loop.

Pressing the accelerator increases the exhaust flow, heting the O2 sensor up, and allows it to begin working normally again.

Couple questions..

Do you have headers?

How long has it been since you changed the O2?

When it's ruinning lean, is this only at idle, or on the highway as well?

 

Saw your sig...you do have headers...might be time to upgarde to a heated O2 sensor when you change it.

 

Mike, the sensor is about a year old and has about 10k miles on it. Yes, I have shorty headers.

I just performed a test that Vader had written - using a propane torch and checking the mV. It check out fine. I know that doesn't show accuracy, just if it's working or not.

Running Lean occurs at different times. Earlier today I held it at partial throttle (about 2800) for about 60 seconds and watched my scanner readings. Said that it was in open loop and the oxygen sensor was not ready, plus it was lean the entire 60 seconds.

 

Let me add that the coolant temperature was about 180* during that test.

 

You may in fact be running lean for some reason. RPMs at 2800...should show consistant o2 crosscounts.

See, the o2 sensor is a conduit for open/closed loop... ECM won't go into closed loop until O2 sensor begins generating crosscounts (above and belkow 450mv bias to ECM).

So, either 02 sensor is at fault...not likely at 10k miles, or you are running lean, keeping 02 sensor under 450mvs...which ECM thinks it's not "warmed" enough to generate crosscounts.

Now, the trick is to find out wether you are actually lean, or too rich and saturating the o2 sensor, which gives a false lean code.

Do a search for "code 44"...save me a lot of typing Do the search on the TPI board too.

How';s the exhaust smell? Normal, or sticky...like too much fuel?

 

Mike, good stuff!

No, crosscounts while scanning for 30 seconds, 8 hits when I let off the gas pedal.

No error codes at all.

O2 mV stayed in the 200s until I let off the gas, peaked at 360mV
BLM - 128
INT - 128
Idle Air Meter - 160
You're on to something, that has to be why I'm staying in open loop. :hail:

How can I richen it up. Running about 48lbs of fuel pressure with vacuum off? :hail:

 

BTW - Actually smells rich - checked the plugs the other day and they looked good - kind of tan color.

 

Forget about fuel pressure..other than at WOT...ECM 'should" compensate for inj pulse width.

If it smells a bit stinky, like rich exhaust, try disconnecting MAF electrical connector (under side of MAF), see if lean reading goes away.

 

Ok, with MAF disconnected I start getting crosscounts, goes from Rich to Lean - back and forth. Still wants to be in open loop, but now seems to jump from open to closed more often.

idle air mtr - stays up around 160.

Does this tell you anything?

 

Hmmn...

IAC at 160...is this with MAF connected? or disconnected? never looked at IAC with MAF disconnected...should think it would be the same...but not sure.

Crosscounts happening with MAF disconnected..indicates MAF may be at fault...causing too much fuel into engine (saturating o2 sensor) causing false lean condition. (from your descrpription of smelling rich)

Did you search on code 44 (I know you have no codes, but the search is relavant to your problem) ?

 

Another thing about IAC..160 means IAC is near (if not) fully retracted, trying to let in as much air as possible.
This issue may be as simple as buying a 10 dollar TB gasket kit, and pulliung the TB, taking it apart and cleaning al;l areas, including the passages with a pipe cleaner/toothbrush and carb cleaner.

 

Inside is spotless, all new Edelbrock high flow, ported, polished and cleaned. Unfortunately, It's taken apart fairly often and recleaned everytime.

Yes, searched on code 44 and other related MAF posts. By the looks of the data in my scanner, the MAF seems to be functioning. Been searching on MAF Burnoff relay to see if that could be a problem. Not sure what the symptoms would be if it failed.

Thanks for your time and attention. If you think of anything else, let me know. I'll keep at it from here.

:rockon:

 

Why you need to look at the unusual suspects, is because....


IAC at 160...this means ECM is trying tro allow more air into engine...while at the same time you are running lean (via scanner readings)

This means something is fubar.

Since TB is clean, obviously rule this out.

Also (on my short sightedness) it could be ruled out since issue happens above idle.


If MAF burnoff is the undelying issue, then yes, check for burnoff, but realize that the wires in the MAF need to be cleaned,,which lead back to the MAF being at fault.....in one out of 99 chances, you're able to descreen the MAF, clean the wires, and not mess anything up.



Your problem, really seems like the MAF is going south... I happen to be part of the "code 44 team" from years back...you're probably okay to run as-is...keep an eye on things, if car begins to suffer badly, watch the O2's...if they dive to the low mv's and a lean code 44 is present, and you have unburnt fuel stinking up the garage....and it all goes away when you disconnect the MAF....you've identified the problem.