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2000 Silverado 5.3

charlesbwright

By charlesbwright
in Ask A GM Technician

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Jsdirt Senior Enthusiast

Jsdirt

Posted
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Your trims aren't that bad, but they're not lean - they're on the rich side (computer is pulling fuel away - hence the "negative" trim).

 

Is that a Flex engine? Not sure if they had that back in '00. If not, you could have an EVAP purge valve stuck open. That will make it  misfire like crazy, especially after a fill up at the gas station - sometimes they won't start after filling up, especially if you fill the tank right to the top of the filler neck all the time.

 

Normally that will flag the "money light", though.

carkhz316 Enthusiast

carkhz316

Posted
Posted

Can you open a graph display of the upstream O2 sensors and log that while driving? Or at least indicate what the display is showing when your truck acts up? I would be inclined to think, based on some rich long term fuel trims, that you're suffering from a ignition miss, presumably under load (most common) which would explain the chugging at highway speed. Alternatively, if it were indeed secondary ignition problems (plugs and wires), you could put your foot on the brake and rev it to TC stall (don't do a burnout), to see if the engine starts missing.

charlesbwright Enthusiast

charlesbwright

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6 hours ago, carkhz316 said:

Can you open a graph display of the upstream O2 sensors and log that while driving? Or at least indicate what the display is showing when your truck acts up? I would be inclined to think, based on some rich long term fuel trims, that you're suffering from a ignition miss, presumably under load (most common) which would explain the chugging at highway speed. Alternatively, if it were indeed secondary ignition problems (plugs and wires), you could put your foot on the brake and rev it to TC stall (don't do a burnout), to see if the engine starts missing.

Did as u said PEG the throttle first gear only, what's upstream downstream on obd

Screenshot_20190318-164539.png

charlesbwright Enthusiast

charlesbwright

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8 hours ago, Jsdirt said:

Your trims aren't that bad, but they're not lean - they're on the rich side (computer is pulling fuel away - hence the "negative" trim).

 

Is that a Flex engine? Not sure if they had that back in '00. If not, you could have an EVAP purge valve stuck open. That will make it  misfire like crazy, especially after a fill up at the gas station - sometimes they won't start after filling up, especially if you fill the tank right to the top of the filler neck all the time.

 

Normally that will flag the "money light", though.

Not flex from knowledge 5.3 vortec 

charlesbwright Enthusiast

charlesbwright

Posted
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Posted

Ok notice omw home from work and omw to work seems more frequent in second gear, I know I should here difference in exhaust and rpm but it almost goes quite, happen earlier running 30 -45, at 1500 rpm, didn't buck any or chuga chuga lol, but I could hear in exhaust sounded like I was just likely tap throttle. Also noticed that oil pressure is on low side in my opinion at idle it's 40 driving around 60 could this be the problem. I really appreciate all the help from everyone, I could take it to mechanic anytime but I'd rather do it myself

 

Jsdirt Senior Enthusiast

Jsdirt

Posted
Posted

 You have plenty of oil pressure. You'd hear the engine tick at idle if you didn't. Doesn't take much to make an LS get noisy.

 

I have no idea what I'm looking at with that graph. Like I said, your upstream o2 sensors (bank 1 sensor 1 [B1S1], and bank 2 sensor 1 [B2S1] ) should peg rich on a full throttle run - .700 -.900 volts. If they're switching, or pegged lean, you have a fuel delivery problem.

 

EDIT: If that graph is a capture of when you were at full throttle, everything looks good - o2s are rich, and having no cats, the downstream look as I'd expect, confirming the upstreams are working.

 

In light of this, I'd agree with Carkhz316 - you may have an ignition issue - plugs, wires, coils, or coil control.

charlesbwright Enthusiast

charlesbwright

Posted
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2 hours ago, Jsdirt said:

 You have plenty of oil pressure. You'd hear the engine tick at idle if you didn't. Doesn't take much to make an LS get noisy.

 

I have no idea what I'm looking at with that graph. Like I said, your upstream o2 sensors (bank 1 sensor 1 [B1S1], and bank 2 sensor 1 [B2S1] ) should peg rich on a full throttle run - .700 -.900 volts. If they're switching, or pegged lean, you have a fuel delivery problem.

 

EDIT: If that graph is a capture of when you were at full throttle, everything looks good - o2s are rich, and having no cats, the downstream look as I'd expect, confirming the upstreams are working.

 

In light of this, I'd agree with Carkhz316 - you may have an ignition issue - plugs, wires, coils, or coil control.

Definitely spark plugs where issue I don't thing they had ever been change, I just finished changing plugs (that far back plug on left is a bitch)and wires, check coil packs earlier been driving 15 mins include idle seem fine no hesitation no bucking and takes off like when I first got it

20190318_210933.jpg

20190318_210938.jpg

Jsdirt Senior Enthusiast

Jsdirt

Posted
Posted

Good deal - glad it was an easy, relatively cheap fix. :thumbs: :cheers:

charlesbwright Enthusiast

charlesbwright

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1 minute ago, Jsdirt said:

Good deal - glad it was an easy, relatively cheap fix. :thumbs: :cheers:

Appreciate all the help man thanks 

Jsdirt Senior Enthusiast

Jsdirt

Posted
Posted

No problem, Brian. Have a good night.

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