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02 sensor

87BrnRsd

87BrnRsd

1/2 ton status
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Apr 21, 2003
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Boone, North Carolina
I recently added a set of headers on my 87 350 tbi K5, and was told that I should use a 3 wire 02 sensor. Where can I get this 02 sensor, and how doI wire up a 3 wire if I only have a 1 wire now? Thanks.
-Harrison
 
Thanks for the reply. I have searched around on the web and am having a hard time finding this part. Where can I find it? Also, I am currently running open headers but will be adding more exhaust later. This truck is not daily driven so it doesnt really see much road use. Will the 3 wire heated 02 sensor function correctly with open headers? Right now the truck is running ok, but has a hesitation and runs like crap for the first 5 seconds of startup on EVERY startup. After that it clears up, but I can definitely tell something is not right. I just purchased a cable to hook my laptop up to my truck and I have winaldl so I will be able to look at whats going on. I dont think the current 02 sensor is working right at all considering its in open headers at the end of the collector, I have no idea how old it is, and last time I went wheeling, I had the truck up to the bottom headlights of water in a creek crossing and I could hear water covering the header collectors as I mashed the gas. It made a burbling sound and Im sure it soaked the 02 sensor. With that said, the truck didnt seem to run any better or worse after the water. Thanks.
-Harrison
 
If the sensor is near the "exit" of the exhuast, then yes, under light loads for sure (less exhaust flow/velocity) there is certainly going to be contamination from the ambient air.

However, O2 isn't looked at on a cold start, so that isn't going to affect that problem.

If I was home I'd go look the number up on the part bag for you, but since I'm not, all I can do is suggest searching the "tech article" forum (the part number thread) or if not there, go over to thirdgen.org and search for "afs-74 part number" without the quotes, and perhaps without the - between the afs and 74.

I even searched for you, but couldn't find it. At least based off my username, but I thought I had posted it.

Anyways, I think ac-delco.com(sp?) will let you cross reference between GM PN and the Delco AFS-74.

http://coloradok5.com/forums/showthread.php?t=53116&page=3&highlight=afs so I'm bored, sue me. :) My post on that page. Page 4 (top post?) lists the 3 wire vehicle side connector for it, not sure with pigtail or not, but probably costly, I'd go wrecking yard, although I've had a hard time finding the O2 sensor connector on the newer stuff, even the S10's, it's so compact/stuffed in there.
 
Do you have any idea what would cause it to surge and almost stall on startup every time warm or cold? I am completley stumped. It does it every time for about 5 seconds, thens smooths right out. It only showed up after I installed an edelbrock performer tbi intake, and a set of afterburner headers. Its really annoying.
-Harrison
 
I actually havent had any time to mess with it much at all yet. I am currently waiting on a usb adapter so I can hook the truck up to my laptop and run winaldl. It should be here tomorrow or tuesday. When I go to do that, I will check to see if I can find any vacuum leaks. Thanks for the help.
-Harrison
 
I have headers on my 89 and still use the one wire O2 sensor with no SES light.Just make sure that if you added a bung for the sensor that the weld
doesn't leak.After you add full exhaust the problem with ambient cooler air
will be gone.I had also read about using a three wire O2 sensor but I have had this one wire setup for almost a year now and no problems.:D
 
I think the problem with the ses light on mine is that I dont have full exhaust. Are you running a full exhaust? Whenever I get a full exhaust on mine, I dont think it will be a problem anymore. However, I will probably still switch to a 3 wire sensor because I believe my 02 sensor is worn out and a 3 wire is about the same cost IIRC.

The problem with crappy idle on startup is definitely caused by something else though. It does it at the first startup of the day with the engine completley cool, which tells me that its not the 02 sensor because it isnt even picking up a reading yet. Im going to search for vacuum leaks next week. Could the timing being off by a tooth cause this? Could it be the computer advance that is catching it up and making it run fine after those first 5 seconds?:dunno:
-Harrison
 
I am running a full exhaust.The only reason that i brought up the bung weld was because i had a pinhole leak around the bung on my headers and got a code for the O2 sensor.I took the K5 to the local exhaust shop and the guy found the leak and spot welded it.After i reset the SES light,it never came on again.:D
 
All I run is headers into a single 3" with a flowmaster right after the Y and a dump. I doubt if my whole exhaust system is over 3' long. I have no problems with a single wire 02. Goes into closed loop right when it should.
If your truck is running bad when starting cold check your coolant temp sensor. But if you think you neen a heated 02 go to CFM tech as said above otr turbocity.com Both have them.
 
If you aren't watching (scanning) it though, you might never be going closed loop and the ECM may never throw a code. Mine runs fine, but appears to rarely, if ever, go closed loop.

I've gotta read up on the parameters of O2 sensor operation, as it is fairly common for them to "drop out" of closed loop, and they don't throw a code. Mine will sit out of closed loop at idle for minutes on end and no code, because of the O2 sensor.
 
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