Eliminating O2's

[1slow95]

Hey guys, I could be way off here, but I was thinking and the one time that I can remember that my car idled perfectly I found out one of my O2 sensors had a couple wires cut. So I'm curious, can I try unplugging my O2 sensors and driving the car? I know they're not even used at WOT(right?), but how would it behave during normal driving? If the car runs great without the O2's, can I just leave them unplugged?

:SNSign:

 

[94v6GT]

Im guessing if you disconnect them, your gonna throwcodes and the ecu might do some funny stuff. but if you leave 'em hangin in air the comp will think they are defective and throw codes. just a guess though

 

[95Mustang302]

yeah no o2 sensors can cause big problems with the computer, plus your gas mileage will go even further into the toilet

 

[1slow95]

But why would the car run better with two of the O2 wires cut? Or it could be something totally different and I'm focusing on the O2's for no reason.

This is what the car sounds like most of the time, http://www.mustangaddiction.com/movies/miss.wmv. I don't know if it's supposed to do that, but it doesn't sound right to me. And it seems to be getting worse.

 

[1TallMF]

Yeah, that does sound a bit off (sounds friggin amazing besides that ).
I think its probably more of a coincidence than anything else. I wouldn't be running it without O2's. The computer would not have a way to measure and adjust the afr, and would have to rely on previously stored average values. You'd deffinetly be leaving power on the table and getting uber-****tty gas mileage

 

[Pokageek]

Check your intake manifold bolts upper and lower if you haven't already. When I took my stuff off the 306 to get ready for the new engine, I couldn't believe it but a few bolts I could hand loosen!

 

[Rootus]

Are those kooks header longtubes? Where are the O2 sensors located relative to the head? I could easily see having the car run better in open loop than closed if the O2 sensors are far enough from the head to have heating problems.

I've seen people force open loop to try and get their car running properly, and it can be made to [mostly] work. Problem is that you lose the ability of the ECU to compensate for any condition that comes up which causes the real AFR to differ from the target AFR.

 

[1slow95]

 

[Rootus]

Yup, too far. At idle the O2 sensors cool off and start reading a false lean condition, which causes the ECU to add fuel. On mine it would happen as soon as I started idling, and within a few minutes the trims would be maxed out. If you cannot find a way to keep the sensors hot enough to function right, your best bet may be to try and force open loop just at idle. I would try to keep CL operation available for non-idle so that you can benefit from ECU learning (the sensors should stay warm enough when exhaust flow is higher).

Or move the O2 sensors into a primary tube on each side. That has it's own downsides of course.

Or go with shorties.

I'd go see what they're saying in the tuning sub-forum or over on the TwEECer boards. It's been a long time since I was TwEECing my own car, so better techniques may have been devised for dealing with this situation.

 

[BlownFiveLiter]

You can tune without the O2 sensors, but you lose a very valuable feature of the EEC, being the adaptave strategy. Stephane is correct in believing that without them, it runs on the tables that it has programmed into it, but it has no way to compensate for any change in AF. I'm not really sure what to suggest beyond that, unless there's a way to move the bungs closer to the engine, or into a primary like Rootus said, but then if you're experiencing a lean or rich condition in any particular cylinders, you won't know it unless it's the cylinder that has the O2 sensor in the primary.

 

[HISSIN50]

Dave's idea to run OL at idle would be what someone like me would have to do.

 

[Don 95Vert]

Both my Gen 1 Turbo Lighhtning and our SN95 turbo are run in OL all the time. We do this because the 02 sensors internal heaters do not get enough 'help' from the exhaust because the turbos 'steal' too much heat. They run OK at first, then all kinds of problems start. There are several European countries where Fords are also run in OL all the time. The tune has to be spot in to do this and not have mileage to go in the crapper. You cannot just remove the 02 sensors without doing a few things in the tune though.

BTW: Some late model V10 F-series run in CL all the time from the factory!

Don

 

[kck6894]

I run my car without 02's. My collectors leak enough that I can't use them. I didn't see much differance in milage, but I did loose some. Make sure to reset your computer if you unhook them. If your computer doesn't see the 02's when it comes online it won't throw a code.

 

[1slow95]

I have noticed the car seems to run better after I run it hard. It was running really bad the other day when I was idling in traffic.

I run my car without 02's. My collectors leak enough that I can't use them. I didn't see much differance in milage, but I did loose some. Make sure to reset your computer if you unhook them. If your computer doesn't see the 02's when it comes online it won't throw a code.

Thanks, I will give that a try.

Don, I have an SCT chip, if unplugging the O2's will cause a problem even after resetting the computer, could you make the necessary changes if I mailed my chip to you? Or would you need the car there?
What about setting just the idle to OL, would that be possible?

Thanks!
:SNSign:

 

[1slow95]

I run my car without 02's. My collectors leak enough that I can't use them. I didn't see much differance in milage, but I did loose some. Make sure to reset your computer if you unhook them. If your computer doesn't see the 02's when it comes online it won't throw a code.

How long should I leave the battery unhooked for the computer to reset? I left it for about 20 minutes, unplugged the O2's, then after about 10 minutes of driving the CE light came on. The car did seem to run better for the 15 minutes I had it out. The idle still isn't quite right, but it is better now. Plus it might have fixed another problem I was having, I was able to cruise in 5th at 40mph with no missing/bucking.

 

[tjh566]

Disconnect the battery and turn on your lights, thats what Ive always done to clear the comp.

 

[Don 95Vert]

Yes, disconnect the battery and turn on the lights or step on the brake 5-6 times.

Yes, I could reburn the SCT chip to run in OL, but it really cannot be done via mail order. We'd need the car here and we'd need to do a point-by-point MAF re-calibrations to make sure it's as close as it can get.
Don

 

[1slow95]

Yes, disconnect the battery and turn on the lights or step on the brake 5-6 times.

Yes, I could reburn the SCT chip to run in OL, but it really cannot be done via mail order. We'd need the car here and we'd need to do a point-by-point MAF re-calibrations to make sure it's as close as it can get.
Don

I figured you would need the car there...I've got some other things I need to take care of first, plus if the car continues to run as good as it did yesterday I can live with the CE light for a while. I'll get back to you once the car is ready, but it'll probably be a while.

I'll try resetting the computer again and take the car for a longer drive. I'll post up the results later this week.

 

[1slow95]

CE light comes on occasionally, but I can live with that for now. The car runs much smoother now but driveability suffered a little bit(bucking/surging at low rpm). I'll get it retuned one of these days when I have the cash. I have other more important problems to fix at the moment.

I now think my O2's were just going bad. A friend of mine had the same missing problem mine had and replacing the O2's fixed it. I would rather just get rid of them than replace them every year.