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73-87 Chevy _ GMC Trucks => Fuel Systems and Drivability => Topic started by: Unofficial on November 04, 2010, 11:08:48 AM
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Hey guys, I'm having some problems with my '87. It's a 350 TBI with not even 800 miles on the new motor. I put headers on a long time ago, so I had to modify my oxygen sensor setup. With the factory exhaust, the sensor was after the y-pipe in the manifolds, but with the headers, I have the sensor in bung on the the driver's side header only, I no longer have a y-pipe. The oxygen sensor is fairly new, but I keep getting codes for it. First I was getting code 44, which is a lean condition. Thinking it had something to do with my adjustable fuel pressure regulator, I put the old non-adjustable regulator in. I reset the ECM to clear the codes, and now I'm getting code 13 again. This has happened before, so I put a new wire in, thinking that may have been the problem. I'm only getting about 12-13 mpg, and that's driving it REALLY easy. I didn't take it over 2,000rpms for a week and I still ended up with 12 or 13 mpg. This seems awfully low considering I have throttle body injection, a 700r4, and 2.73 gears. I drive for roughly ten minutes on the highway to school cruising at about 1800rpms. Any ideas on how to solve this? Code 13 is open circuit for oxygen sensor by the way.
Thanks in advance
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Just a stab in the dark, but if you're sure the wire to the sensor is not the problem maybe you're not getting a good ground to the header. Its hard to imagine that, but I've seen stranger things. Are they coated headers?
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There are two identical connectors that will fit the O2 sensor. Do you have it connected to the right one?
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I'm positive it's the right connection. The headers are not coated. The light usually comes on if I run it hard or go highway speeds for a long period of time.
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I wish I got 12mpg with my '87 tbi 350 and TH700....
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Did you use the sensor that you splice into the plug or the type that you plug into the plug
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If I remember right, it was a plug-type. The wire was too short though so i clipped off the two plugs and put a new wire in to make it reach.
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Are you sure the fuel pump is good? It may not be blowing fuses but it may be too weak to keep up with engine load.
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Well I guess the fuel pump may be possible, but I don't think that would have anything to do with an open circuit code for the oxygen sensor
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I would double check the wires to make sure
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Hey, I'm bumping this thread because I ran a new wire from the oxygen sensor to it's plug, and I'm still getting code 13 after resetting the ECM. I'm still getting around 11 to 12 mpg. I remember seeing a way to test the oxygen sensor circuit on ALLDATA, but I no longer have access to it.
Does anyone know how I can figure this out? Read first post for more info on my truck. Thanks for any help.
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If I remember right, it was a plug-type. The wire was too short though so i clipped off the two plugs and put a new wire in to make it reach.
Wait you cut the O2 sensor wire on the sensor side or the harness side?
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If I remember right, it was a plug-type. The wire was too short though so i clipped off the two plugs and put a new wire in to make it reach.
Wait you cut the O2 sensor wire on the sensor side or the harness side?
Oh yeah I forgot to mention that...When I looked at it again I guess I was wrong, I never clipped that plug off. So I cut it on the sensor side.
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but you still cut the wires. it could be a bad connection not letting the o2 sensor send the right signal
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Cutting the wire has nothing to do with getting the code, it was throwing code 13 with the oxygen sensor before the one with the longer wire that I made. The connection is fine anyway.
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ow did you splice the wires?
If you did not solder it, the wire itself will cause enough resistance that the O2 sensor won't read properly.
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Cutting the wire has nothing to do with getting the code, it was throwing code 13 with the oxygen sensor before the one with the longer wire that I made. The connection is fine anyway.
On the single wire O2 sensor (zirconia element) the O2 sensor becomes a voltage generator with a range of 0-1volt when it reaches approximately 600°F but it needs to be able to breathe. It reacts to the Oxygen it receives through the wire on the outside of the body. Depending on where and how you cut the sensor wire can greatly effect its performance. You should have cut the harness side not the sensor side.
Look at this pic -
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Alright, I see what you mean. I cut it on the sensor side, but on the very end, not near the actual sensor.
So what are my options now? I'm going to buy a new sensor because when I was running the new wire the other day, it looks like something hit the sensor and bent that plastic housing a little bit.
Is that the only thing I can do? I'd like to buy a new harness for the sensor because I messed it up when I was running the new wire but I'm not sure I can even buy that...
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You should be able to buy a universal sensor for your truck it comes with out the plug but with longer wires. Also a little cheaper
http://www.autozone.com/autozone/parts/Bosch-Oxygen-Sensor/1987-Chevrolet-R10-1-2-ton-P-U-2WD/_/N-iigfvZ8gcvp?counter=0&filterByKeyWord=o2&fromString=search&itemIdentifier=4966_54956_5320_
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You should be able to buy a universal sensor for your truck it comes with out the plug but with longer wires. Also a little cheaper
http://www.autozone.com/autozone/parts/Bosch-Oxygen-Sensor/1987-Chevrolet-R10-1-2-ton-P-U-2WD/_/N-iigfvZ8gcvp?counter=0&filterByKeyWord=o2&fromString=search&itemIdentifier=4966_54956_5320_
That's usually what I get, I've never gotten one that comes with the plug. Can I cut out the plug and just run a straight wire? I know it's a stupid question, but it would be even more stupid to do it without making sure first right? :D
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Universal ones are junk. The OE style is cheap enough
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Well I got a bunch of work done today after my classes.
I put in a new throttle cable, put on my winter wheels/tires, got an OE O2 sensor and put it in. An OE sensor is only $18.99 so whatever. This time I lengthened the wire on the harness side, and kept the sensor wire like I bought it. I'm hoping for no engine code this time around. Thanks for the help guys, I'll post back if the light comes on again.
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Universal ones are junk. The OE style is cheap enough
how they, they are made by the same company and if he needed a longer wire then I would think one splice would be better than 2 or 3 granted if it was a stock setup yes I would say go with oe but something has to be cut and no it doesn’t have to have the plug its more there for a almost guarantee connection
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There's a reason they're cheaper and it's not because the connector costs $150 + or more and of course unwanted voltage drops/resistance. I take it since you are familiar with them you know they can't be soldered and the connections they come with are about as cheesy as you can get.
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Well after only a day of driving after putting in the new sensor, code 13 is back.
I'm about to take it to a shop, this is ridiculous.
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So far all you have done is verified your O2 sensor is good essentially. I'll assume you don't have a scan tool? Go directly to the ECM with your VOLT meter. DO NOT USE AN OHM METER. Backprobe cavity D7 of the ECM with the engine at operating temperature running at about 2000 RPM. The voltage should switch between .100V and .900V. If it does you know your signal is getting to the ECM. Next check the ground circuit which at this point if your signal is getting there you probably left the ground wire off at the back of the cylinder head. Cavity D6 of the ECM should have continuity to ground (at the engine block).
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Just a thought....
You are NOT putting any sealer or anything on the O2 sensors threads are you?
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Just a thought....
You are NOT putting any sealer or anything on the O2 sensors threads are you?
Every O2 sensor I've ever bought has what I think is anti-seize already applied on the threads.
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That's fine. Check those things I posted above.
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That's fine. Check those things I posted above.
Would you happen to have a diagram showing which cavity that is? I tried google but I can't seem to find a good picture. How should I probe it? Stab a paper clip in there?
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Stab isn't the word I would use... backprobe it with a T-pin
http://ocw.weber.edu/automotive-technology/ausv-1320-automotive-electronics/10-trouble-shooting/back-probing-terminals
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Well I finally got around to testing it, and I'm getting voltage to the wire.
I'm gonna go check for a ground wire I might have missed... but wouldn't I be having other problems if I missed a ground wire?
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You mean the O2 voltage is getting to the ECM? That ground is specifically the ECM ground for that circuit. It's one or the other so if the voltage is getting to the ECM then your problem is the ground circuit.
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Well I went from d6 to the engin block and had pretty high resistance, so now what?
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So you probably left that ground wire off. Did you check the grounds at the back of the cylinder heads?
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BTW it's a tan wire ckt 413 and should be grounded directly to the engine block.
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Ok sweet, I'll look for it. Where can I find this wire?
Kinda weird that I was getting this code before I swapped motors...
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I can't seem to find this wire...Can anyone give me a specific location?
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Do you have continuity from that wire to ground?
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Because if you don't that ground wire is off. There are two wires going to the outlet. There should be one at the thermostat housing and two at the back of the cylinder heads.
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Well I finally got around to checking it out and I took some pictures...
(http://i112.photobucket.com/albums/n187/w00ty_01/12-12-10042resize.jpg)
Here's the one at the thermostat housing like you mentioned Vile
(http://i112.photobucket.com/albums/n187/w00ty_01/12-12-10049resize.jpg)
I looked for the two wires you said should be grounded to the back of the cylinder head and I found these...As you can see, one of the wires doesn't have insulation on it all the way to the end, but I didn't think that would cause an open circuit, the bolt is on there tight. What's next?
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Do you have continuity from that wire to ground?
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Well I used an ohmmeter going from the d6 cavity to the back of the engine block and got like 50 ohms, so I figured that was bad... I'm sorry, I'm not so good with this electrical stuff, how do I test for continuity? Go from d6 to that wire this time? What should I measure this time? Ohms again?
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That wire is spliced into the DLC as well. I would suggest you tap into that wire and run another dedicated clean engine ground.
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That wire is spliced into the DLC as well. I would suggest you tap into that wire and run another dedicated clean engine ground.
DLC=Data Link Control?
Which of the three wires should I come off of for another ground?
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DLC = Data Link connector
splice it at the ECM as close to the connector as you can and run a new engine ground. Make sure your engine has a good ground as well to the frame and the frame to the body.