Exhaust problems

GMC1994K1500SierraSL · Aug 15, 2018

Hey guys, just picked up a 94 Chevy Silverado 1500 with a 350, ran great when I first took it out, tried to drive it the other day it was hesitating and dying at idle, check engine light came on and I was able to get code 13 out of it, light comes and goes and the serverity of the RPMs going up and down, I crawled under my truck this evening after getting a new O2 sensor and to my surprise the O2 sensor was welded in place, I cannot change it now and I’m trying to figure out what to do now (truck ran and idled fine this evening)

Whoever installed this exhaust did a true dual, no cross over, the O2 sensor is only reading on one bank, is that ok on a TBI? What can I do to fix this? With the drivers exhaust pipe running beside my passenger one I assume I need to cut out that section of pipe and install a new piece with the threaded spot for my sensor so the truck can run normally again or atleast better on fuel I’m thinking it was running rich as I could smell gas every once in a while

Here are some pics

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jdla140 · Aug 16, 2018

I believe that the older TBI engines only had one o2 sensor in the driver side exhaust manifold, way upstream of the y-pipe so having it in only 1 pipe with true duals shouldn't cause too much issue. If it does you could always weld in an x pipe or h pipe to equalize flow. They make weld in bungs for o2 sensors, one of those may be your best bet.

Sucks that they welded it in though, def a bass ackwards way to do it.

jdla140 · Aug 16, 2018

I believe that the older TBI engines only had one o2 sensor in the driver side exhaust manifold, way upstream of the y-pipe so having it in only 1 pipe with true duals shouldn't cause too much issue. If it does you could always weld in an x pipe or h pipe to equalize flow. They make weld in bungs for o2 sensors, one of those may be your best bet.

Sucks that they welded it in though, def a bass ackwards way to do it.

evilunclegrimace · Aug 16, 2018

That O2 is not welded on , it is rusted in place. Take a torch and heat it up and it should unscrew

94burbk1500 · Aug 16, 2018

Looks like the bung is welded (as it should be), but not the sensor, you can see the nut for the sensor. Clean it up some and I bet you'll be able to see where they meet. Like Grimace said, a little heat is your friend.

retorq · Aug 20, 2018

jdla140 said:
I believe that the older TBI engines only had one o2 sensor in the driver side exhaust manifold, way upstream of the y-pipe so having it in only 1 pipe with true duals shouldn't cause too much issue. If it does you could always weld in an x pipe or h pipe to equalize flow. They make weld in bungs for o2 sensors, one of those may be your best bet.

Sucks that they welded it in though, def a bass ackwards way to do it.

My O2 sensor was in the Y pipe, 95 TBI.

GMC1994K1500SierraSL · Aug 20, 2018

Had to go to a shop to get a new chunk of pipe put in, O2 sensor was welded in the bung by the last guy who worked on it, there’s a lot of hackery on this truck

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c1500deathtrap · Sep 9, 2018

Earlier TBI engines ran 1 o2 sensor in the drivers side manifold. See picture. They moved it when they added the heated oxygen sensors (o2 sensors need heat to read) so the older 1 wire 02 sensors need to be close to the header/manifold collector to reach operating temp. if you have a heated oxygen sensor (3 wire or more), then placement is less vital.

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Exhaust problems

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