Any ideas on what would cause such large deviations between the O2s?
Thread Starter
TECH Fanatic
iTrader: (2)
Joined: Dec 2001
Posts: 1,648
Likes: 3
From: Wilmington, MA
Any ideas on what would cause such large deviations between the O2s? I took my car to the track tonight after my header install to get it dialed in. However, my O2s are way off from each other. .050-.070, in fact. For example, in 3rd gear for 3 runs, I averaged about .900-.910 readings on B1S1 and .950-.970 on B2S1. I leaned it out a bit with my MAFT and got .880-.890 on B1S1 but B2S1 was still in the .940 range.
I have a 12" o2 extension on the driver's side, and no extension on the passenger side (just yanked the wires out of the harness to make them reach, hehe).
Could an O2 be damaged? Or the wiring?
I don't think there's any leak at the flange (where the headers attach to the head) as there is no ticking or anything like that, and I would assume an exhaust leak that close to the engine would be very loud.
Any ideas?
Thanks
Dope
I have a 12" o2 extension on the driver's side, and no extension on the passenger side (just yanked the wires out of the harness to make them reach, hehe).
Could an O2 be damaged? Or the wiring?
I don't think there's any leak at the flange (where the headers attach to the head) as there is no ticking or anything like that, and I would assume an exhaust leak that close to the engine would be very loud.
Any ideas?
Thanks
Dope
Re: Any ideas on what would cause such large deviations between the O2s? Swap the 02s and see if the numbers change banks with the swap. If not, maybe an exhaust leak, faulty/clogged injector(s) ?
TTT for you. <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />
Bad30th
TTT for you. <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />
Bad30th
Thread Starter
TECH Fanatic
iTrader: (2)
Joined: Dec 2001
Posts: 1,648
Likes: 3
From: Wilmington, MA
Re: Any ideas on what would cause such large deviations between the O2s? Good idea, I didn't think about swapping them (obviously). Will try that and see if the problem follows the sensor. Hopefully it does and I can get it replaced. If not, I'll try using the extension on the other side instead. If that doesn't change it either, there's gotta be an exhaust leak, but I really don't think so. If I open the hood while the car idles, it is as quiet or quieter than it was stock! Definitely no ticking.
Dope
Dope
Re: Any ideas on what would cause such large deviations between the O2s? Remember you also have the post-cat O2s to test with. They're all interchangable, so you should be able to verify by swapping and monitoring whether it's O2s or not.
Swapping fuel injector banks can also be done to try to isolate the problem if it turns out not to be O2s.
Free stuff is always good to test first. <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" />
Also FWIW it's normal to have a little variance between the two banks, and it's more common to have a wider variance if you're tuned to positive LTrims (i.e. lean). Supposedly going into negative LTrims evens the two banks out somewhat.
Tuning with the MAFT seems to have two camps :
1) Tune to +8/+10 LTrims and gain a few degrees of timing
2) Keep slightly negative LTrims for more even O2 banks and no fuel enrichment at WOT, no gain in timing but more even tuning
Most have said that the extra few points of timing gained by camp #1 haven't shown any gains above camp #2 tuning, and that having the ECM arbitrarily adding fuel from the last known LTrim at WOT is a bad idea.
I am getting Ed Wright programming next week with my heads/cam upgrade and will be interested to see where the fuel trims are afterwards.
Good luck,
Bad30th
Swapping fuel injector banks can also be done to try to isolate the problem if it turns out not to be O2s.
Free stuff is always good to test first. <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" />
Also FWIW it's normal to have a little variance between the two banks, and it's more common to have a wider variance if you're tuned to positive LTrims (i.e. lean). Supposedly going into negative LTrims evens the two banks out somewhat.
Tuning with the MAFT seems to have two camps :
1) Tune to +8/+10 LTrims and gain a few degrees of timing
2) Keep slightly negative LTrims for more even O2 banks and no fuel enrichment at WOT, no gain in timing but more even tuning
Most have said that the extra few points of timing gained by camp #1 haven't shown any gains above camp #2 tuning, and that having the ECM arbitrarily adding fuel from the last known LTrim at WOT is a bad idea.
I am getting Ed Wright programming next week with my heads/cam upgrade and will be interested to see where the fuel trims are afterwards.
Good luck,
Bad30th
