I bought a 4.3 97 gmc sierra that was neglected for prob years as far as the simple things it needed done. Mostly everything was carboned and running under very Rich conditions for some years .
I found that the Eng-1 fuse that actually controls the o2s and the cam sensor was removed and seems
they did this too purposely run the truck in open loop . The only way it will run half way decent.
So the upstream o2 was cut and demolished and the downstream was missing.. I had NEW o2 bungs welded in place and put in new "Up steam and down stream o2 sensors ac delco brand. Removed and cleaned the tbi thoroughly it was filth carboned up ..cleaned the egr pintle that was stuck at 10% open per a code. Cleaned the mass air and
Cleared codes also with new plug wires new air filter.
Truck on a scan tool live data shows ST Fuel trim fluctuates between
37-39 on both banks. LT fuel trim sticks at 25 that seemed good too me . The pcm seemed too relearn the system as it idled everything smoothed out slowly on first start .. engine had no vibrations or hesitation and the rich gas smell was gone etc etc..
" Except Now the EGR pipe smolders"
steam/smoke off that nylon type heat covering after I drive it half mile . Not while it's at idle ... Only when I get a mile down the road I stop check under hood...Its almost as if something isn't working on egr itself or the system if finally trying to do its job and it's seeing issues or the cat has been clogged maybe ? Or the egr pipe is full carbon. But it don't sputter as a clogged cat would kill an engine or sputter or glow red .
Finding that Eng-1 fuse missing seemed real purposeful like the tell all be all . It was a old fella who wrenched on trucks and ran a farm... so I can tell he could care less as long as the truck Moved .. so he ran the truck with no fuse just too get around a rich condition he didn't want to track down or spend$ on.
I'm boggled as to how it can run well like it should after the new o2s in and new cam sensor plug wires air filter and all the cleaning done but yet the steam off the egr pipe worries me . It seems like maybe the egr functions are trying too work after all these years and it's maybe dealing with some type of blockage built ??? so I won't drive it .
Only thing it could be else wise is engine degreaser I used when I first got the truck is burning off that for saturated in the heat material cover they use on the egr tube. But I power washer the hell out of the top end. I took the Eng-1 fuse our end it drives ok idles higher .. burns gas more but the EGR pipe don't smolder .
I can't afford too drive this in open loop too get around. And I don't wanna waist more$ yet . I could cut the cat off and delete it or trust in EGR Delete kit. Or maybe it's the egr bad itself . Any ideas ???
This is the live data with the Eng-1 fuse in and working like it should or trying too work.
Fuel trims Short term reads 50
Long term reads 25 on both bank
Maf LB 0.68 at idle
MAP HG" 10.6 idle
which I would assume are good normal readings . Except I had a code come up saying the downstream o2 wasn't sensing or working and it' is brand new. I wondered it the egr situation and or cat is causing that Or I have a bad o2 new out of the box.
I found that the Eng-1 fuse that actually controls the o2s and the cam sensor was removed and seems
they did this too purposely run the truck in open loop . The only way it will run half way decent.
So the upstream o2 was cut and demolished and the downstream was missing.. I had NEW o2 bungs welded in place and put in new "Up steam and down stream o2 sensors ac delco brand. Removed and cleaned the tbi thoroughly it was filth carboned up ..cleaned the egr pintle that was stuck at 10% open per a code. Cleaned the mass air and
Cleared codes also with new plug wires new air filter.
Truck on a scan tool live data shows ST Fuel trim fluctuates between
37-39 on both banks. LT fuel trim sticks at 25 that seemed good too me . The pcm seemed too relearn the system as it idled everything smoothed out slowly on first start .. engine had no vibrations or hesitation and the rich gas smell was gone etc etc..
" Except Now the EGR pipe smolders"
steam/smoke off that nylon type heat covering after I drive it half mile . Not while it's at idle ... Only when I get a mile down the road I stop check under hood...Its almost as if something isn't working on egr itself or the system if finally trying to do its job and it's seeing issues or the cat has been clogged maybe ? Or the egr pipe is full carbon. But it don't sputter as a clogged cat would kill an engine or sputter or glow red .
Finding that Eng-1 fuse missing seemed real purposeful like the tell all be all . It was a old fella who wrenched on trucks and ran a farm... so I can tell he could care less as long as the truck Moved .. so he ran the truck with no fuse just too get around a rich condition he didn't want to track down or spend$ on.
I'm boggled as to how it can run well like it should after the new o2s in and new cam sensor plug wires air filter and all the cleaning done but yet the steam off the egr pipe worries me . It seems like maybe the egr functions are trying too work after all these years and it's maybe dealing with some type of blockage built ??? so I won't drive it .
Only thing it could be else wise is engine degreaser I used when I first got the truck is burning off that for saturated in the heat material cover they use on the egr tube. But I power washer the hell out of the top end. I took the Eng-1 fuse our end it drives ok idles higher .. burns gas more but the EGR pipe don't smolder .
I can't afford too drive this in open loop too get around. And I don't wanna waist more$ yet . I could cut the cat off and delete it or trust in EGR Delete kit. Or maybe it's the egr bad itself . Any ideas ???
This is the live data with the Eng-1 fuse in and working like it should or trying too work.
Fuel trims Short term reads 50
Long term reads 25 on both bank
Maf LB 0.68 at idle
MAP HG" 10.6 idle
which I would assume are good normal readings . Except I had a code come up saying the downstream o2 wasn't sensing or working and it' is brand new. I wondered it the egr situation and or cat is causing that Or I have a bad o2 new out of the box.
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