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Discussion Starter · #1 · (Edited)
My voy has developed a strange issue. If you start it cold it'll idle just fine and smooth and start warming up like normal. Once it's warmed up either by sitting and idling or driving since I tested both it will eventually start to stink, idle poorly/almost stall then it'll catch itself and idle at 900RPM. When this happens if the battery had been reset the SES light immediately comes on with P0171. You can still feel it stumble as well and it'll idle itself up to 25-30 but it won't almost stall anymore.

The exhaust smells not like gas, but more like mothballs or bleach or perhaps like a ceramics kiln's exhaust instead of the Vortec's haha. There's no smoke even at WOT but man this thing is a stink bomb once this problem starts. It does not smell at all like this while it's cold and warming up. Sometimes the 900RPM idle randomly stops and it'll idle back to 600 but still reek, then it'll stumble and almost stall and back to 900. Muffler/Resonator have been removed but cat is still there. Truck has just under 240k miles. I've also tried fuel from 3 separate gas stations pretty far apart from another in case it was bad fuel.

My current guess is the fuel pump is slowly dying, working normally until it gets hot then struggling and the fuel pressure drops creating the smell and the lean code. I sprayed the intake manifold, vacuum lines with carb cleaner but the engine speed didn't increase. I'm going to rent a fuel pressure tester today and get the cold/hot pressures and report back I just wanted to pick everyones brain to see if there's someone else that's had a similar situation. Another thing is I don't notice a decrease in performance just the smell. If the fuel PSI dropped wouldn't the engine be way down on power?

EDIT- Sorry forgot to mention the fuel filter was changed right after the first time this happened as I was meaning to do it anyway.
 

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My voy has developed a strange issue. If you start it cold it'll idle just fine and smooth and start warming up like normal. Once it's warmed up either by sitting and idling or driving since I tested both it will eventually start to stink, idle poorly/almost stall then it'll catch itself and idle at 900RPM. When this happens if the battery had been reset the SES light immediately comes on with P0171. You can still feel it stumble as well and it'll idle itself up to 25-30 but it won't almost stall anymore.

The exhaust smells not like gas, but more like mothballs or bleach or perhaps like a ceramics kiln's exhaust instead of the Vortec's haha. There's no smoke even at WOT but man this thing is a stink bomb once this problem starts. It does not smell at all like this while it's cold and warming up. Sometimes the 900RPM idle randomly stops and it'll idle back to 600 but still reek, then it'll stumble and almost stall and back to 900. Muffler/Resonator have been removed but cat is still there. Truck has just under 240k miles. I've also tried fuel from 3 separate gas stations pretty far apart from another in case it was bad fuel.

My current guess is the fuel pump is slowly dying, working normally until it gets hot then struggling and the fuel pressure drops creating the smell and the lean code. I sprayed the intake manifold, vacuum lines with carb cleaner but the engine speed didn't increase. I'm going to rent a fuel pressure tester today and get the cold/hot pressures and report back I just wanted to pick everyones brain to see if there's someone else that's had a similar situation. Another thing is I don't notice a decrease in performance just the smell. If the fuel PSI dropped wouldn't the engine be way down on power?

EDIT- Sorry forgot to mention the fuel filter was changed right after the first time this happened as I was meaning to do it anyway.
A bad catalytic converter will smell like a stink bomb if it goes bad
 

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A bad catalytic converter will smell like a stink bomb if it goes bad
Also a bad fuel injector or powerpack can cause the catalytic converter to fail since raw fuel is dumped and saturated in the cat. Since you mentioned fuel I thought I'd add that to support the idea of a bad cat.
 

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Discussion Starter · #4 ·
That would make a ton of sense too if it's the converter, as it won't stink until it gets hot. I don't have emissions so I'll just go have a muffler shop replace it with a test pipe and report back. I'll have to get the CEL turned off somehow. I've been wanting a tune anyway, thank you!
 

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Discussion Starter · #6 ·
Ok I checked the fuel pressure and it was a steady 50-52psi with no fluctuation. Shutting the truck off it dipped to about 47 and didn't move. I noticed the O2 sensor values were really strange. With the engine off the upstream O2 read 0.45v then once started kept going lower and lower and eventually bottoming out at out 0.05-0.04v and going down to 0.00v when the engine was off. Downstream O2 with the engine off was at 0.75 then jumped to pretty much 1v and stayed there. I attached a screenshot.

I also noticed I have an exhaust leak when my head was in there, not sure if it's the manifold or the gasket so I'll change the gasket and inspect the manifold for leaks. Upstream and Downstream O2 sensor is from 2018 and were delco.

Are my O2s just on their way out? I also saw pending O2 sensor code P0133. I think the issue is a dying O2 + exhaust leak. I'll replace both and see what happens since they're pretty cheap.

57761
 

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Discussion Starter · #7 ·
Another update, I just got done driving it about 120 miles at 60-80mph and for the first 20 or so miles it still smelled but after 20 miles it seemed to clear up out of nowhere. I stopped for fuel and pulling into the gas station the truck was back idling at 600 with no stumbles no smells no nothing. Checked the data again and it was quickly fluctuating between ~0.15v and 0.65v.

I'm hoping it's a faulty sensor that works when it wants to and not a wiring problem eek! I'll replace the exhaust manifold gasket/O2 sensor tomorrow and report back.
 

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Discussion Starter · #8 ·
Final update for now, I replaced the O2 sensor and while I was going to take the manifold off the engine I realized that every single bolt was loose, I mean I didn't even have to use a wrench loose. I don't know how this engine didn't sound like it had open exhaust. I got them all torqued and kept the old gasket and all is well! No more exhaust leak sound and the engine seems to be happy. I drove it for 30 minutes at or over 90mph and it's running good with no CEL... yet. I'll report back if this wasn't the fix but I have a good feeling it was. The O2 readings with the new sensor are MUCH faster and go from .30 to .65 but chill out around .50
 

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Discussion Starter · #9 ·
Also, if anyone would like all of the A/C hoses and the accumulator/dryer they're yours if you pay the shipping. I deleted the A/C since my truck has no roof or doors and it was really in the way to get the heat shield out. I have everything except the compressor and evaporator, the system worked just fine I just never used it because it was pointless. Hit me up if you'd like them :)
 

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My current guess is the fuel pump is slowly dying, working normally until it gets hot then struggling Tutuapp 9Apps and the fuel pressure drops creating the smell and the lean code. I sprayed the intake manifold, vacuum lines with carb cleaner but the engine speed didn't increase. I'm going to rent a fuel pressure tester today and get the cold/hot pressures and report back I just wanted to pick everyones brain to see if there's someone else that's had a similar situation. Another thing is I don't notice a decrease in performance just the smell. If the fuel PSI dropped wouldn't the engine be way down on power?

EDIT- Sorry forgot to mention the fuel filter was changed right after the first time this happened as I was meaning to do it anyway.
I recommend you to go to a trusted garage and make a full analysis , and check your oil storage too
 
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