O2 codes at open loop?

Nixon1 · 04-21-2004, 10:55 AM

The other day I got in the car to leave from work and made it around the block before a Check Engine light came on. It would go out for one or two seconds, then come on. Mostly under acceleration. I pulled into the Autozone because for one of their free diagnostics (dont want to buy a code scanner, and I know how to use a paperclip to pull GM codes, but not Ford codes!)... Well the codes came up as 41 and 91, which I was apprised were Left O2 lean, Right O2 lean. (Voltage low.) Now this surprised me because the car hadn't reached full operating temp yet. It SHOULD have still been running open loop operation.

Two days later, I get in the car to leave again, and after idling for about 10 seconds, Check Engine comes on. I turn the car off, and turn the key to Ign. to reprime the fuel pump. I do this twice, then start the car. It idles fine, with no light. As I go to leave the parking lot, I tip in on the gas and the light comes on. Every time I hit the gas pedal, the light came on. I didn't have time to pull THAT code, but I assume it's the same code since the only other code my car has EVER thrown was an MAF (out of range) code from running air filter-less.

What would cause my computer to try to read from the O2's prematurely...or what would cause it to even try to go into closed loop before it's ready? I thought AT LEAST the CTS had to read something like 140 degrees and both O2's had to be hot enough to send variating signal voltage.

The only things I've done to the car recently are remove the oil filler cap and PCV return line, block the manifold fitting, and run a breather (valve cover baffling removed, allowed oil into the return line)....and my evap system is currently open-ended. There was a pinhole in manifold line there, so I plugged the manifold fitting. I was going to buy more vacuum hose, but the fitting on the sensor that the gases pass through snapped off, so I left it open. Also note, the car was very low on fuel...the needle was right above the empty mark. Could this have anything to do with my problem? I can't imagine any kind of vaporlock induced by running an open-ended and not an actively pulled evap system, since EFI motors run high line pressure.

I checked my fuel pressure after the codes and, of course, I couldn't get the Check Engine light to come on again. Pressure read 42 at idle, and MOST of the time when I revved the motor, it would spike up to around 48 or so. Although sometimes the pressure would DIP instead, down to about 39. New injectors, AFPR installed.

Sorry the post is so long, but there's a LOT of details I wanted to include. Any help is appreciated. My motorcycle just got hit so it's in a repair shop right now, and I can't afford to have my only other vehicle break down!

canukracer · 04-21-2004, 03:45 PM

my alldata says 41-91 lean condition and or lack of switching. check for contaminated engine oil,check pcv vavle for damage or blockage then fuel psi, maybe your reroute of pcv vavle is doing it

04-21-2004, 04:51 PM

Sorry to hear about your bike. Hope you weren't on it when it got hit?! Just because your check engine light came on at a "certain time"...doesn't mean you were necessarily throwing the code right at that moment. The check engine light can come on from a code it through the day before maybe...or from the week prior. You can even read your codes when your check engine light is not flashing...and quite often there will be some stored codes in there. You might want to check that orange ground wire for the O2 sensors and make sure it's grounded. It's located right behind the upper intake/ throttle body area...coming out of the big 'ol wiring harness there.

Also, it probably doesn't have anything to do with the codes you are pulling...but I've heard that the tube running from your oil filler tube to your throttle body should in fact be hooked up to vacuum. I'm not sure of the specifics...but having it hooked up to the throttle body is supposed to help suck out the exhaust gases out of the combustion chamber &/or crank case. Something like that. Anyway...I've had mine unhooked from my TB for years now. I too have my baffle in my valve covers removed due to the 1.72 rockers. I had a tube running from the oil fillter tube down near my charcoal canister into the open air. I've also ran a breather. I've been told that even if some oil does spit up there due to the baffle being removed that it won't hurt anything...and that the motor may actually run better & more effeciently with the tube hooked up to the throttle body, the way it came from the factory.

Anyone else have any theories on this rubber hose running from the oil filler tube on the passenger side valve cover to the throttle body??

Nixon1 · 04-21-2004, 04:53 PM

Lack of switching? As in, lack of switching to or from open to closed loop??

As far as engine oil goes....I changed it about 500 miles ago. Had small metal particles on my magnetic drain plug, but nothing major. My engine tore up some pushrods real bad a little while back so I got the drain plugs and all cause I couldn't do a tear-down and complete flush.

The PCV valve is around a year old or so...it SHOULDNT have any problems! Although I hesitate to throw around the word 'shouldnt'. And also, Ive had my PCV return system disabled for about a month now....I would imagine it would start showing these problems much sooner, instead of waiting so long, unless somehow I damaged something. Which I don't even see how I could. But I don't know, I'm lost.

Fuel psi, I mentioned in my enormous writeup...lol. 42 at idle, sometimes when I rev it'll spike up like it should, othertimes it'll dip. Maybe my fuel pump is having problems? Sometimes on an initial prime, it'll only build 15 or 20 psi...but after it's been primed a few times, it'll consistently build full pressure.

canukracer · 04-22-2004, 11:31 AM

the switching is from lean to rich, not open to closed loop so the code is sayin o2 is in lean condition meaning it's running rich, it will have somthing to do with both banks because it's flaging both o2's lean

Dark_5.0 · 04-22-2004, 12:05 PM

Quote:

Originally posted by Nixon1
Lack of switching? As in, lack of switching to or from open to closed loop??

As far as engine oil goes....I changed it about 500 miles ago. Had small metal particles on my magnetic drain plug, but nothing major. My engine tore up some pushrods real bad a little while back so I got the drain plugs and all cause I couldn't do a tear-down and complete flush.

The PCV valve is around a year old or so...it SHOULDNT have any problems! Although I hesitate to throw around the word 'shouldnt'. And also, Ive had my PCV return system disabled for about a month now....I would imagine it would start showing these problems much sooner, instead of waiting so long, unless somehow I damaged something. Which I don't even see how I could. But I don't know, I'm lost.

Fuel psi, I mentioned in my enormous writeup...lol. 42 at idle, sometimes when I rev it'll spike up like it should, othertimes it'll dip. Maybe my fuel pump is having problems? Sometimes on an initial prime, it'll only build 15 or 20 psi...but after it's been primed a few times, it'll consistently build full pressure.

If what you say about your fuel pressure is true then the fuel pump is most definitely your problem.

Change that sucker out and you should be good to go. Takes about 2 hours if you take your time.

Piece of cake.

HISSIN50 · 04-24-2004, 08:43 PM

it is normal from what i gather to have the FP dip when you rev the motor. it depends upon how much vacuum was removed while revving (real fast rev vs a slower rev where vac is maintained).

PCV is bi-directional. if one is worried about it, runnin a catch can and filter is the best route, as far as i know.

as said, codes are stored in KAM. you can check the values of the lambdas warm and cold (closed loop occurs around 170-178*, IIRC).

but since both banks are lean, i would really check the primary systems first. as said, FP could be it (Dark 5.0, i was not refuting you or trying to be a jerk - just stating what i thought i knew. it sounds like you are pretty sure about what you said, and i have no reason to doubt it!).
also your MAF being outta whack or dirty can cause bad input.

one last thing i can think of- you might want to check your ECT and ACT. one or the other may be telling the puter that the car is warm and ready for closed loop, when in fact the car is cold, thus causing a lean condition. but when running codes, the sensor checks out ok, as it is within parameters, albeit not the correct ones for the situation.

just my two cents worth.
good luck.

04-21-2004, 10:55 AM	#1
Nixon1 Registered Member Join Date: Jan 2003 Location: Palm Bay, FL Posts: 432	O2 codes at open loop? The other day I got in the car to leave from work and made it around the block before a Check Engine light came on. It would go out for one or two seconds, then come on. Mostly under acceleration. I pulled into the Autozone because for one of their free diagnostics (dont want to buy a code scanner, and I know how to use a paperclip to pull GM codes, but not Ford codes!)... Well the codes came up as 41 and 91, which I was apprised were Left O2 lean, Right O2 lean. (Voltage low.) Now this surprised me because the car hadn't reached full operating temp yet. It SHOULD have still been running open loop operation. Two days later, I get in the car to leave again, and after idling for about 10 seconds, Check Engine comes on. I turn the car off, and turn the key to Ign. to reprime the fuel pump. I do this twice, then start the car. It idles fine, with no light. As I go to leave the parking lot, I tip in on the gas and the light comes on. Every time I hit the gas pedal, the light came on. I didn't have time to pull THAT code, but I assume it's the same code since the only other code my car has EVER thrown was an MAF (out of range) code from running air filter-less. What would cause my computer to try to read from the O2's prematurely...or what would cause it to even try to go into closed loop before it's ready? I thought AT LEAST the CTS had to read something like 140 degrees and both O2's had to be hot enough to send variating signal voltage. The only things I've done to the car recently are remove the oil filler cap and PCV return line, block the manifold fitting, and run a breather (valve cover baffling removed, allowed oil into the return line)....and my evap system is currently open-ended. There was a pinhole in manifold line there, so I plugged the manifold fitting. I was going to buy more vacuum hose, but the fitting on the sensor that the gases pass through snapped off, so I left it open. Also note, the car was very low on fuel...the needle was right above the empty mark. Could this have anything to do with my problem? I can't imagine any kind of vaporlock induced by running an open-ended and not an actively pulled evap system, since EFI motors run high line pressure. I checked my fuel pressure after the codes and, of course, I couldn't get the Check Engine light to come on again. Pressure read 42 at idle, and MOST of the time when I revved the motor, it would spike up to around 48 or so. Although sometimes the pressure would DIP instead, down to about 39. New injectors, AFPR installed. Sorry the post is so long, but there's a LOT of details I wanted to include. Any help is appreciated. My motorcycle just got hit so it's in a repair shop right now, and I can't afford to have my only other vehicle break down! __________________ '91 Mustang GT 5.0 AOD Daily Driver Current stats: NEW 302 short block, E-303 cam (@.050, 220/220, .498/.498, 110 degrees), 1.6 roller rockers, Performer RPM heads (aluminum, 1.9/1.6, 60cc chambers), Cobra intake, Granatelli 75mm MAF, Billet AFPR, Equal-Length Shorty Headers, Off-Road X Pipe, Flowmasters, 4.10 POSI 13.73 at 103.8, ~2.2 60'

04-21-2004, 04:51 PM	#3
Simi Stang Guest Posts: n/a	O2 & evap Sorry to hear about your bike. Hope you weren't on it when it got hit?! Just because your check engine light came on at a "certain time"...doesn't mean you were necessarily throwing the code right at that moment. The check engine light can come on from a code it through the day before maybe...or from the week prior. You can even read your codes when your check engine light is not flashing...and quite often there will be some stored codes in there. You might want to check that orange ground wire for the O2 sensors and make sure it's grounded. It's located right behind the upper intake/ throttle body area...coming out of the big 'ol wiring harness there. Also, it probably doesn't have anything to do with the codes you are pulling...but I've heard that the tube running from your oil filler tube to your throttle body should in fact be hooked up to vacuum. I'm not sure of the specifics...but having it hooked up to the throttle body is supposed to help suck out the exhaust gases out of the combustion chamber &/or crank case. Something like that. Anyway...I've had mine unhooked from my TB for years now. I too have my baffle in my valve covers removed due to the 1.72 rockers. I had a tube running from the oil fillter tube down near my charcoal canister into the open air. I've also ran a breather. I've been told that even if some oil does spit up there due to the baffle being removed that it won't hurt anything...and that the motor may actually run better & more effeciently with the tube hooked up to the throttle body, the way it came from the factory. Anyone else have any theories on this rubber hose running from the oil filler tube on the passenger side valve cover to the throttle body??

04-21-2004, 04:53 PM	#4
Nixon1 Registered Member Join Date: Jan 2003 Location: Palm Bay, FL Posts: 432	Lack of switching? As in, lack of switching to or from open to closed loop?? As far as engine oil goes....I changed it about 500 miles ago. Had small metal particles on my magnetic drain plug, but nothing major. My engine tore up some pushrods real bad a little while back so I got the drain plugs and all cause I couldn't do a tear-down and complete flush. The PCV valve is around a year old or so...it SHOULDNT have any problems! Although I hesitate to throw around the word 'shouldnt'. And also, Ive had my PCV return system disabled for about a month now....I would imagine it would start showing these problems much sooner, instead of waiting so long, unless somehow I damaged something. Which I don't even see how I could. But I don't know, I'm lost. Fuel psi, I mentioned in my enormous writeup...lol. 42 at idle, sometimes when I rev it'll spike up like it should, othertimes it'll dip. Maybe my fuel pump is having problems? Sometimes on an initial prime, it'll only build 15 or 20 psi...but after it's been primed a few times, it'll consistently build full pressure. __________________ '91 Mustang GT 5.0 AOD Daily Driver Current stats: NEW 302 short block, E-303 cam (@.050, 220/220, .498/.498, 110 degrees), 1.6 roller rockers, Performer RPM heads (aluminum, 1.9/1.6, 60cc chambers), Cobra intake, Granatelli 75mm MAF, Billet AFPR, Equal-Length Shorty Headers, Off-Road X Pipe, Flowmasters, 4.10 POSI 13.73 at 103.8, ~2.2 60'

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
KOEO & continuous memory codes??	Simi Stang	Windsor Power	4	12-16-2003 02:37 PM
Pulled codes...what do they mean?	Hethj7	Windsor Power	8	06-12-2003 12:03 PM
Pulled New Codes Today	Mountain Main	Windsor Power	11	06-11-2003 02:10 AM
Codes me too	Just me	Windsor Power	8	07-29-2002 12:06 AM
Open loop mode??	89LX50Coupe	Windsor Power	3	06-11-2001 09:00 AM

04-21-2004, 03:45 PM	#2
canukracer Registered Member Join Date: Jul 2003 Location: alberta canada Posts: 108	my alldata says 41-91 lean condition and or lack of switching. check for contaminated engine oil,check pcv vavle for damage or blockage then fuel psi, maybe your reroute of pcv vavle is doing it

04-22-2004, 11:31 AM	#5
canukracer Registered Member Join Date: Jul 2003 Location: alberta canada Posts: 108	the switching is from lean to rich, not open to closed loop so the code is sayin o2 is in lean condition meaning it's running rich, it will have somthing to do with both banks because it's flaging both o2's lean

04-24-2004, 08:43 PM	#7
HISSIN50 Registered Member Join Date: Mar 2004 Posts: 62	it is normal from what i gather to have the FP dip when you rev the motor. it depends upon how much vacuum was removed while revving (real fast rev vs a slower rev where vac is maintained). PCV is bi-directional. if one is worried about it, runnin a catch can and filter is the best route, as far as i know. as said, codes are stored in KAM. you can check the values of the lambdas warm and cold (closed loop occurs around 170-178*, IIRC). but since both banks are lean, i would really check the primary systems first. as said, FP could be it (Dark 5.0, i was not refuting you or trying to be a jerk - just stating what i thought i knew. it sounds like you are pretty sure about what you said, and i have no reason to doubt it!). also your MAF being outta whack or dirty can cause bad input. one last thing i can think of- you might want to check your ECT and ACT. one or the other may be telling the puter that the car is warm and ready for closed loop, when in fact the car is cold, thus causing a lean condition. but when running codes, the sensor checks out ok, as it is within parameters, albeit not the correct ones for the situation. just my two cents worth. good luck.