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Unread 03-19-2013, 08:48 AM   #1
Jbwardfamily
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Howell TBI O2 Sensor Question

I have the Howell TBI (non-California) system installed in my 79 CJ w/304 and have headers. It has worked great for 9 months. Recently, I have been getting the check engine light for code 13. This is the O2 sensor. Troy said it could either be the sensor itself or the computer. It came with the heated sensor and has 2 wires coming from it. Every replacement I have seen only has one wire. Can I replace a 2-wire sensor with a 1-wire sensor? Shouldn't O2 sensors last much longer than 9 months? I am exempt from all vehicle inspections so there is no emission control left on the CJ. It still runs fine and Troy said it won't affect anything long term other than maybe a little bit of mpg, however, the light is aggravating and I want it to work like it is supposed to.

Thanks,

James

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Unread 03-19-2013, 08:51 AM   #2
walkerhoundvm
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You'll probably need the heated sensor with headers. Can Troy give you a part number to replace? A little mpg, but I'm thinking it's running out-of-loop so is basically acting like a semi-adjusted carb at this point; you're not getting the best bang for your buck and Howell really should have those part numbers on hand.

I agree, O2 sensors should last more than a few months :/
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Unread 03-19-2013, 09:43 AM   #3
Jbwardfamily
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They have them in stock at Howell, but they are $60. I hate to throw that kind of money at a "maybe" fix. The other option is to send the ECM back to have it re-flashed. I use my CJ as a daily driver and hate to lose it for a week. Is there any way to test the sensor? I have a voltmeter.
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Unread 03-19-2013, 09:55 AM   #4
CSP
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There has to be a stock application that's a replacement. It's garbage that Howell won't give the original application out so you can get replacement parts. What if you're stuck far from home and can't wait for them to ship you their $60 part?

I would dig around in the EFI forums at www.binderplanet.com and see if you can find a part number for the two wire, heated sensor.
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Unread 03-19-2013, 10:38 AM   #5
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There has to be a stock application that's a replacement. It's garbage that Howell won't give the original application out so you can get replacement parts. What if you're stuck far from home and can't wait for them to ship you their $60 part?

I would dig around in the EFI forums at www.binderplanet.com and see if you can find a part number for the two wire, heated sensor.
Heated sensors have 3 or 4 wires and, as far as I know, are only used on the Howell California Emissions kits (mine is a 4-wire).

Two-wire sensors are un-heated. One wire is the signal, and the other is the "zero-reference" or ground. This way the O2 sensor ground is not through the exhaust pipe/manifold, which is usually isolated by gaskets or rubber hangers.

Any 2-wire O2 sensor can be used as a replacement. I'm not sure what the p/n or application for an exact match is, but I bet if you take yours down to Napa, they'll be able to get you a direct replacement.


Also, O2 sensors need to be kept relatively clean so they have a good "free-air" reference. If there is any dirt, mud, or grease buildup on the sensor body (especially near the wires) that could cause it to not function properly.
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Unread 03-19-2013, 10:59 AM   #6
CSP
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Where in the world did I get "two wire, heated sensor" from? Thanks for that correction SLO Ken!

Pretty sure that I use any '89-90 GM S10 pickup or blazer as an application for the O2 sensor when I've done TBI swaps. It's a direct fit and that's what the Howell TBI setup is based on.
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Unread 03-19-2013, 11:08 AM   #7
Jbwardfamily
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I mentioned that I had a 2-wire heated sensor. I thought that is what I ordered when I got the kit. Could be wrong. So, if it only has 2 wires, it is not heated? I have headers and the sensor is installed in the collector between the header and muffler. If I do not have a heated sensor, should I?
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Unread 03-19-2013, 11:21 AM   #8
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My understanding is that, that far from the engine you should have a heated sensor.
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Unread 03-19-2013, 11:31 AM   #9
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Originally Posted by walkerhoundvm
My understanding is that, that far from the engine you should have a heated sensor.
x2.

I don't have the CA, but I do have a heated sensor for use with my headers. I have two piece headers with the heated sensor (4wires) in the 1 cylinder exhaust. 258 here, but you get the gist.
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Unread 03-19-2013, 11:48 AM   #10
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I mentioned that I had a 2-wire heated sensor. I thought that is what I ordered when I got the kit. Could be wrong. So, if it only has 2 wires, it is not heated? I have headers and the sensor is installed in the collector between the header and muffler. If I do not have a heated sensor, should I?
I have never seen a heated sensor with fewer than 3 wires. But I haven't been around as long as some others...

O2 sensors only generate a signal above 600*F or so. With yours mounted so far down from the head, I would recommend a heated sensor.
If you decide to replace yours with a heated sensor, make sure it is a "narrow band" sensor. This is the type of O2 sensor that the early 90's GM computers are designed around. They put out 0.7-1.0 V when the exhaust is rich, and 0.0-0.2 when the exhaust is lean. The switch is right around an AFR of 14.7:1.
Wide band sensors output a smooth voltage change from 5-1 V corresponding to AFR's of about 8-20. These are fairly new and are just starting to be widely used in the auto industry.
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Unread 03-19-2013, 11:55 AM   #11
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Wide band sensors output a smooth voltage change from 5-1 V corresponding to AFR's of about 8-20. These are fairly new and are just starting to be widely used in the auto industry.
Interesting info, Ken. Would they have any application with a TBI, how hard would they be to find, and would they be of benefit for mpgs, emissions, etc?
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Unread 03-19-2013, 12:37 PM   #12
SLO_Ken
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Interesting info, Ken. Would they have any application with a TBI, how hard would they be to find, and would they be of benefit for mpgs, emissions, etc?
Factory TBI systems used the narrow band sensors basically as a switch. In closed loop mode, the computer constantly checks the voltage reported from the O2 sensor. If the voltage is above 0.5V, the computer commands less fuel. If the voltage is below 0.5V, it commands more fuel. The catch is that while the narrow band sensor can report if the engine is running too rich or too lean, it can't really tell how much too rich or lean. The engine ends up oscillating between rich and lean while in closed loop computer control.
Also, there are certain situations where you don't want the AFR to be right at 14.7. Under wide-open-throttle (WOT), for example, the ideal AFR may be closer to 12. In this situation, the narrow band sensor can only tell the computer whether or not the AFR is less than 14.7, but it can't tell how close it is to the desired 12. So, the computer ignores the sensor completely and reverts to "open loop" mode and meters the fuel based on stored fuel tables (the "fuel map") rather than feedback from the O2 sensor.

The benefit of a wide band O2 sensor is that it can accurately determine and report AFR as rich as 8:1, and as lean as 21:1. So, the computer can be programmed to have closed loop control of the system in a wider range of conditions. This helps with emissions and MPG. But, unless you were writing your own ECU computer code, probably not too much benefit for a TBI system.

There are stand-alone tuning systems that utilize the wide-band sensors. Innovate LM-2 is one I'm familiar with, but there are others.
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Unread 03-19-2013, 01:45 PM   #13
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The LM has a way to use its wide band O2 sensor as a simulated narrow band output to the PCM.

To the OP if you truely have a two wire sensor I would be interested in knowing that. I have a old speed tune AF monitor from the early 90's and I've never been able to match it up to anything for sale at a auto parts store.

Also that far away from the exhaust ports you need a heated sensor. Running too long in open loop you will run the risk of gassing your oil.

A narrow band sensor works just fine as a AF monitor for a carb. It's nice and steady. I've been using them since 1994 when I roadraced motorcycles. They even can handle leaded fuel.
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Unread 03-19-2013, 02:53 PM   #14
Jbwardfamily
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Ok. Lots of great info here. I took a closer look and I have a 4-wire sensor. All of the wires are in perfect shape. Is there any way the sensor went bad or should I prepare to send the ECM back to Howell? I hate to put $60 into a new sensor. I have never seen one go bad that fast.
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Unread 03-19-2013, 03:23 PM   #15
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Quote:
Originally Posted by Jbwardfamily
Ok. Lots of great info here. I took a closer look and I have a 4-wire sensor. All of the wires are in perfect shape. Is there any way the sensor went bad or should I prepare to send the ECM back to Howell? I hate to put $60 into a new sensor. I have never seen one go bad that fast.
Do you have a volt meter?
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