67speeda Posted September 2, 2011 Report Share Posted September 2, 2011 (edited) I have an 04' with 125,000 miles. I have long tubes and no cats and rear 02 deleted. When is it time to replace the front 02's ???? my fuel eco SUCKS and i was thinking since my intake is clean, throttle body is clean, the tuck runs well, it must be the 02's dropping my economy. (used to be 14-15 with me having fun driving, now it is down to 10-10.5) No CEL is on other specs: performabuilt level 2 2600 converter billet stock muffler (got really sick of loud truck) intake (forgot brand, AEM or something) MSD wires plugs done at 80K edit: wheatley tune Edited September 2, 2011 by 67speeda (see edit history) Quote Link to comment Share on other sites More sharing options...
Krambo Posted September 2, 2011 Report Share Posted September 2, 2011 (edited) You are overdue for an O2 change. You will hear different reasoning and change intervals however, I change my personal fleet at 50k intervals which some may say is overkill. Regardless, the new heated O2's should be swapped by 100K at the latest. Edited September 2, 2011 by Krambo (see edit history) Quote Link to comment Share on other sites More sharing options...
misterp Posted September 2, 2011 Report Share Posted September 2, 2011 I agree with your thinking. My own truck has 90K on it now with the original O2s, and I have been using EFILive a lot this summer logging and learning; I'm running open-loop speed-density (my PCM totally ignores the O2s) and my MPG went from 12-ish to a solid 15+ and my O2s take a long time to heat-up now, plus they are not 'switching' as fast as they used to in scans I logged years ago. IMO I would replace them every 80K-miles or so. Too bad those sensors are so damned expensive. Mr. P. Quote Link to comment Share on other sites More sharing options...
zachm89 Posted September 2, 2011 Report Share Posted September 2, 2011 if im sneaky about it i can get the hook up on 02 sensors...i need to replace mine as well Quote Link to comment Share on other sites More sharing options...
67speeda Posted September 2, 2011 Author Report Share Posted September 2, 2011 if im sneaky about it i can get the hook up on 02 sensors...i need to replace mine as well hummmm PM me what price you can do. def throw you something as well for the troubles.... Quote Link to comment Share on other sites More sharing options...
67speeda Posted September 4, 2011 Author Report Share Posted September 4, 2011 upstream = the front 02 sensor, before the cat, closest to the motor???? just making sure before i order Quote Link to comment Share on other sites More sharing options...
Krambo Posted September 6, 2011 Report Share Posted September 6, 2011 upstream = the front 02 sensor, before the cat, closest to the motor???? just making sure before i order yes Quote Link to comment Share on other sites More sharing options...
Bgreenard Posted September 8, 2011 Report Share Posted September 8, 2011 I am getting 13ish mpg (city) with CAI, headers, aftermarket cats, Magnaflow and Wheatley tune. I have been thinking about turning off the front and rear cats. That may increase my MPG? I thought the PCM uses the O2 sensors to adjust fuel flow?? Any advise would be appreciated. B Quote Link to comment Share on other sites More sharing options...
67speeda Posted September 12, 2011 Author Report Share Posted September 12, 2011 I am getting 13ish mpg (city) with CAI, headers, aftermarket cats, Magnaflow and Wheatley tune. I have been thinking about turning off the front and rear cats. That may increase my MPG? I thought the PCM uses the O2 sensors to adjust fuel flow?? Any advise would be appreciated. B i think you mean 02 I could be very wrong but i dont think you can turn off front 02's. They are used to adjust the fuel trim. (could be wrong) Quote Link to comment Share on other sites More sharing options...
Krambo Posted September 12, 2011 Report Share Posted September 12, 2011 i think you mean 02 I could be very wrong but i dont think you can turn off front 02's. They are used to adjust the fuel trim. (could be wrong) Your correct. If you are using a closed loop tune then you need the primary O2's for the PCM to "trim" your fueling. You may hear of guys doing an OLSD (open loop speed density) tune in where the PCM does not use the primary O2 sensor's feedback to adjust fueling. "Turning off" the rear O2 sensors is essentially just ignoring their feedback regarding catalytic converter efficiency. Quote Link to comment Share on other sites More sharing options...
KJT13 Posted September 12, 2011 Report Share Posted September 12, 2011 I might as well jump in on this. My mileage is killing me lately. I am a hair shy of 150k and on the originals too so yea, they need to be replaced. My question is, I had my rears tuned out to pass inspection after having my cats replaced. I'm still on the factory manifolds, no headers. Should I replace the rears or can I leave em? Sent from my HTC Thunderbolt using Tapatalk. Quote Link to comment Share on other sites More sharing options...
canadianVRss Posted September 13, 2011 Report Share Posted September 13, 2011 I might as well jump in on this. My mileage is killing me lately. I am a hair shy of 150k and on the originals too so yea, they need to be replaced. My question is, I had my rears tuned out to pass inspection after having my cats replaced. I'm still on the factory manifolds, no headers. Should I replace the rears or can I leave em? Sent from my HTC Thunderbolt using Tapatalk. Why would you replace them if they're not being used? They're a little pricey to be replacing needlessly. Quote Link to comment Share on other sites More sharing options...
Krambo Posted September 13, 2011 Report Share Posted September 13, 2011 Yea keith, don't worry about the rears for replacement in your case. Quote Link to comment Share on other sites More sharing options...
KJT13 Posted September 13, 2011 Report Share Posted September 13, 2011 I wasn't planning on it just making sure my decision was the right one. After I asked I thought about it and thought it was dumb but hey, better to be safe than sorry. Sent from my HTC Thunderbolt using Tapatalk. Quote Link to comment Share on other sites More sharing options...
KJT13 Posted September 13, 2011 Report Share Posted September 13, 2011 Another question though. Is everyone replacing them with OEM sensors or if you're using aftermarket, what do you recommend? What's the part # for OE too? Sent from my HTC Thunderbolt using Tapatalk. Quote Link to comment Share on other sites More sharing options...
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