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oxygen sensor, do I need it?

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ugly_blazer

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I have a running 1989 chevy truck (different body style than the K5 if it matters) with a tbi motor that I plan to swap into my 1979 K20. Is the oxygen sensor (I think thats what it is called, it goes in the exhaust manifold) required for the engine to run good? What does it do and what happens if it isn't hooked up? Thanks /forums/images/graemlins/wink.gif
 
You need it.

It's the ONLY thing the engine uses for closed loop operation to govern fuel delivery. (it uses all the other sensors, but at anything other than WOT and cold engine operation, without an O2 sensor, the engine is screwed)

That's WAY simplified, but the short of it is, if converting another vehicle to TBI, change EVERYTHING over, and don't think about cutting corners.

Injected vehicles run good because of the entire package. When you start removing items, you can cause problems that range from minor annoyances to poor performance.
 
Ok, thanks. I just put new headers on the truck with the old carbed motor still in it and will be getting new exhaust put on next week, can I have the exhaust shop weld a "thing?" in there for the sensor? I think that painless wiring has some and the shop may have some also. If it will work, where should ot get welded in at?

I know close to nothing about fuel injection, so i will probably ask many questions once I have started the swap. I have the whole complete truck that still runs, so that should make it a lot easier. I was planning on even using the FI gas tank if it will fit, I guess that will work /forums/images/graemlins/dunno.gif
 
Just as said above with one exception, if you are installing the engine in your 79 truck and retaining the carb from the 79 you do not need the O2 sensor unless your 79 uses one and then you need to use the O2 sensor from the 79 not the 89. (not sure if they are the same or not)

Sounds like you are swapping the entire engine including the TBI so you will need the O2 sensor, and since you have headers you will no doubt need a heated O2 sensor which needs to go into the collector. The problem with most header installs and trying to use an O2 sensor mounted only in one tube is that one tube usually doesn't get hot enough for the O2 sensor to allow the ECM to go into closed loop.
 
Looks like we posted at the same time, I do plan on keeping the TBI.
 
Read the edited portion below for my update for you if you haven't already.
 
Yes, I read it. One more question, when I put the sensor in the collector it will be farther from the engine than it was in the manifold, can the wire to it be lengthened?
 
yes it can but make sure you have a very tight and clean and water proof connection. The best method would be to solder it then heat shrink afterwards. Sounds like you are going to try it with the single wire factory O2 sensor but I will bet you end up needing a heated O2 sensor. The heated O2 sensors have 3 or 4 wires and i'm not sure how they actually are hooked up, maybe someone else can give you details on that. /forums/images/graemlins/thumb.gif
 
Ant idea, do the Ceramic coated headers help to prevent the heated O2 sensor????

Does the better thermal properties of the ceramic header help keep in enough heat????
 
Actually ceramic coated headers help to move heat faster inside the header, and at the same time help underhood temps stay lower.
 
I will check on the heated sensor, I didn't even know there was a difference. Sounds like I need to do some reading first...

Thanks for the info /forums/images/graemlins/peace.gif
 
I am wondering if they retain enough heat to do away with the need for the heated sensor????

/forums/images/graemlins/dunno.gif /forums/images/graemlins/dunno.gif
 
I guess i wasn't clear enough in my last response. Heat travels out of the header quicker with ceramic coated headers therefor the answer would be NO.
 
/forums/images/graemlins/thinking.gif /forums/images/graemlins/thinking.gif /forums/images/graemlins/thinking.gif /forums/images/graemlins/thinking.gif
 
You sure you don't have that backwards? Ceramic doesn't allow heat to pass through. Watched this on my headers when fired up a new engine after a short break-in with manifolds...

The headers were coated, obviously by spraying them with something. Before installation I noticed pretty heavy overspray on the inside of the head flange end of the pipes, but only a few inches into them. When I fired the engine up for the second time, the pipes ONLY started glowing where the overspray ended. There was no mistaking the line where the overspray ended.

Mine aren't coated, and although I haven't watched the cycle, I know my headers retain enough heat to get th O2 to go closed loop at idle, which is where you will have problems normally.

Edit: Bah, mine ARE coated, but not inside. Headers coated on the inside keep in something like 50-100* more heat than uncoated.
 
[ QUOTE ]
I guess i wasn't clear enough in my last response. Heat travels out of the header quicker with ceramic coated headers therefor the answer would be NO.

[/ QUOTE ]
Ceramic coated headers keep more of the heat inside the pipes, keeping the exhaust stream hotter and the underhood temps cooler. This supposedly makes the exhaust flow away from the engine faster, but it will also send more heat out through the exhaust system, so it would be making the O2 sensor hotter as well. /forums/images/graemlins/cool.gif
 
Not trying to get too far off topic but along with the swap you should bite the bullet and get a good scanner. It will really help you to get things running right after the swap.
Also with a scanner, you can tell if the engine goes into closed loop when it is warm. So you will know if you need a heated 02 or not.
 
If it helps at all, when the 02 sensor went bad in my Buick, it started running crappy. Put a new one in, got rid of the "Check Engine" light, eliminated the weird smell (i think it was from running rich but idk), and jumped gas mileage from 17 mpg to 25 mpg (combined city and hwy). This was on a 3.8L V6. I'd say do it!
 
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