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o2 sensors and A/F reading

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starjammir

Hard-core CEG'er
Joined
Aug 14, 2004
Messages
2,307
Location
Lapeer, Mi
Hey guys,
I got my car tuned from NPG last year and this year I put a sho shop y pipe in it. The y pipe only had one bung so I put the wideband in it and took the other o2 sensor out. I now have 3 CELs for the o2 sensor that is missing. My A/F on the wideband is 15.4 driving, peg lean when at idle, and around 14.6 at WOT. The weird thing is that after I run it pretty hard the car stinks of burning fuel from being to rich. Will the missing O2 sensor cause my car to run this weird? Another CEGer who was driving behind me confirmed that the car was running rich by smelling it a few car lengths back.
Thanks,
Bill
 
starjammir said:
Hey guys,
I got my car tuned from NPG last year and this year I put a sho shop y pipe in it. The y pipe only had one bung so I put the wideband in it and took the other o2 sensor out. I now have 3 CELs for the o2 sensor that is missing. My A/F on the wideband is 15.4 driving, peg lean when at idle, and around 14.6 at WOT. The weird thing is that after I run it pretty hard the car stinks of burning fuel from being to rich. Will the missing O2 sensor cause my car to run this weird? Another CEGer who was driving behind me confirmed that the car was running rich by smelling it a few car lengths back.
Thanks,
Bill
Click to expand...

I am in the same boat as you, and my tuner mentioned that he can't do anything about the gas smell. Only thing i can do and he said it also, install cats. :)

That is amazing 14.6 at wot....ouch. Correct me if i am worng....but you running at 15.4 is running lean and 14.5 is still lean...i was running 11.5 when i did my fuel readings.
 
starjammir said:
Will the missing O2 sensor cause my car to run this weird?
Click to expand...
No. The second O2 on each bank is just a monitor for the precats. It has zero affect on driveability... at least that's the case with factory programming, (I'm minus an O2 myself). I don't see any reason for a tuner to make adjustments based on cat monitor readings, but I guess you never know. You should call NPG. Like everyone else said, 14.6 at WOT is lean... dangerously so IMO. Do you stay at 14.6 to redline?
 
do you have headers or stock manifolds? if you still have stock manifolds, the pre-cats are why its running lean. if you have headers, then you deffinitely need to get it checked out.
 
Nope I have headers, sho shop y pipe, bassani cat back. No cats on the car though. I have to do something about my car though. When spraying a 65 shot it is at 12.5 or so. It is a Zex wet kit.
Yes the car stays around 14.6 WOT, give or take a few points, the whole time. I have no secondaries.
 
sounds like you probably have a fueling issue if it goes to 12.5 when you spray with a wet kit but only 14.6 without it.
 
starjammir said:
Nope I have headers, sho shop y pipe, bassani cat back. No cats on the car though. I have to do something about my car though. When spraying a 65 shot it is at 12.5 or so. It is a Zex wet kit.
Yes the car stays around 14.6 WOT, give or take a few points, the whole time. I have no secondaries.
Click to expand...
The PCM would adjust fuel for any bolt-ons that you have, including dropping the secondaries, given a matched PCM, MAFS & injectors.

Either your tune is garbage, your O2 is off, or you've got an engine problem. Is it missing at all? Can you flash it back to stock to diagnose? Can you datalog? I'd be interested to know what your fuel trims look like.
 
SicSE said:
The PCM would adjust fuel for any bolt-ons that you have, including dropping the secondaries, given a matched PCM, MAFS & injectors.

Either your tune is garbage, your O2 is off, or you've got an engine problem. Is it missing at all? Can you flash it back to stock to diagnose? Can you datalog? I'd be interested to know what your fuel trims look like.
Click to expand...

Well I cant flash it back to stock due to having no secondaries. It would not run at all from what I understand. I tried to re upload the tune due to thinking that it was just missing something. The car when I let off the gas goes POP POP POP POP and shakes. Dunno if that is a mis or just unburned fuel inside the exhaust.
I doubt my wideband is off though due to it being a year old. I can datalog it though. Let me know what you want and ill get it tonight.
 
I got some datalogs if anyone can take a look for me id greatly appreciate it. It looks like the WOT A/F is around 13.5-13.7 or so now. Dunno why. Idle is peg lean though, off the wideband calc. I got some WOT runs with it too.
Thanks guys,
Bill
 
What was your idle AFR? when you had the 13.5 WOT run?

What rpms are you most lean at..... etc or send me the runs to look at.
( i can always pass them along....this weekend)


Honestly it doesn't sound like its the car because you bought t it long ago running great (correct?). It sounds from other people (cough) that the tune was the culprit the day you loaded it in.
 
starjammir said:
Well I cant flash it back to stock due to having no secondaries. It would not run at all from what I understand.
Click to expand...
I'm running a gutted LIM on my hybrid. I didn't have any problems going from functioning secondaries to none at all. You've definitely got a f*cked-up tune if your PCM can no longer adjust for changes in air intake. :shrug:

starjammir said:
I got some datalogs if anyone can take a look for me id greatly appreciate it. It looks like the WOT A/F is around 13.5-13.7 or so now. Dunno why. Idle is peg lean though, off the wideband calc. I got some WOT runs with it too.
Thanks guys,
Bill
Click to expand...
13.5 is MUCH better... though still lean IMO, especially since you're squirtin'.

The tune probably didn't touch any idle settings. Factory programming keeps A/F about as lean as possible at idle.

You can send me your WOT datalogs or just post them here & we can all check 'em out. You'd probably be BEST to have the tuner look them over though, (was it Joey?). Did you call NPG?
 
Harry, SicSe, PM me your emails and I would gladly pass the datalogs along to you guys. NPG did tune it and it was from Tom. No idea what is going on with it though.
Harry- my idle A/F was off the wideband lean. It is beyond 18.0, thats all I know. It shows up as - - - on the wideband.
According to my WOT runs, my lean peaks are at: 2321, 4032, and 4549 RPMs. It is peg rich 10.0 at 5476 though. It all 3 gears!!! Weird!
Cruising around just messing around, it is staying steady at 15.7-16.1 at 3k. I am so confused!
It also looks like my o2 bank 2 fnt sensor is not working. It seems to be at .005-.008v I got a CEL for this too.
 
starjammir said:
It also looks like my o2 bank 2 fnt sensor is not working. It seems to be at .005-.008v I got a CEL for this too.
Click to expand...
This could possibly explain a lot. Does the voltage hold steady at hot idle? If so, there's definitely a problem. If you're talking about it holding steady at WOT, that is normal, but idle is a different story. You should be in closed loop at idle once the engine is warm, and the voltage on both upstream O2's should rhytmically fluctuate somewhere near 0 to near .9 and back to near 0. The PCM continually richens, then leans the fuel to watch for the O2 switching between a rich, (.9), and a lean, (0).

Anyway, if you're lucky, that upstream O2 is bad and throwing off your closed loop fuel trims, which is throwing everything else off. If you're NOT lucky, you're getting extra fuel, a bad burn, or no burn on one or more cylinders on that bank and you might have a big problem. Do you have one of your old O2's that were in there as CAT monitors? If so, you can grind away the little alignment tabs on the connector & plug it in where the possibly-bad O2 is. That should confirm or discount an O2 problem.
 
Do another set of logs when the car is warmed up. You need to get the car to operating temp before you can put faith in any numbers. If that bank2 O2 reads the same way on a hot engine, it's likely garbage & you should swap it with another known-good O2 to verify.
 
The car was warmed up in those datalogs. I have a mustang themo in the car so it doesnt get above 180 usually.
 
starjammir said:
The car was warmed up in those datalogs. I have a mustang themo in the car so it doesnt get above 180 usually.
Click to expand...
The 110°-122° ECT in your idle log is no where near warm regardless of what thermostat you have in there. Though after looking over things again, I'd say that O2 has definitely taken a sh*t. It's physically impossible for a properly running engine to maintain an exact O2 voltage like your bank 2 is showing. Replace that O2, then give the PCM at least a few days of your style of driving to adjust the fuel trims and whatnot. Then do another set of logs.
 
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