99 Silverado 1500 4wd 5.3L - Sputtering

[Brawndo]

I have a 99 Silverado with 260,000 miles that is experiencing a misfire of sorts.

When I am idling, the truck runs great. When I accelerate, there is random hesitations, sounds and feels like I am running out of gas.

Recently replaced plugs and wires. Going to replace Fuel Filter today. I can't get any codes to come up. SES light won't come on for this problem, it does work though. I run the scanner and everything seems to be running fine.

Has anyone experienced anything like this.

Thanks,
Billy

[j cAT]

Originally Posted by Brawndo

I have a 99 Silverado with 260,000 miles that is experiencing a misfire of sorts.

When I am idling, the truck runs great. When I accelerate, there is random hesitations, sounds and feels like I am running out of gas.

Recently replaced plugs and wires. Going to replace Fuel Filter today. I can't get any codes to come up. SES light won't come on for this problem, it does work though. I run the scanner and everything seems to be running fine.

Has anyone experienced anything like this.

Thanks,
Billy

remove o2 sensor upsteam ones if it runs better cat's plugged. run with o2 hole open so exhaust can escape. or put pressure gauge in hole and should be low pressure like less than 5psi at idle etc....

[Brawndo]

Upon initial test drive, fuel filter has done the trick.

It is interesting you mention the cat. The truck had been throwing a cat code, but it kind of went away. I was about to replace cat when I noticed light did not come back on after being reset. I drove straight to inspection station and got her taken care of there.

I'll probably break down and replace the cat if it happens again. I'm looking to dump the truck in the next few weeks, so I just need it run ok.

Thanks

[Brawndo]

I tracked the misfiring down to a coil that had coolant dripping on it.

Now I have a problem where once the truck heats up, basically once the temp guage hits 200-210, I have a hesitation when slowly accelerating.

I can expose this issue the best when the truck is in overdrive at say 45-50mph, and I go to speed up, but without dropping into a passing gear, the entire truck hesitates as if the ignition cut off and right back on.

As mentioned before, I was throwing at passenger side Cat code, but it kind of went away. I reset it in an attempt to get through inspections and after the third reset, it never came back.

Any ideas?

[j cAT]

Originally Posted by Brawndo

I tracked the misfiring down to a coil that had coolant dripping on it.

Now I have a problem where once the truck heats up, basically once the temp guage hits 200-210, I have a hesitation when slowly accelerating.

I can expose this issue the best when the truck is in overdrive at say 45-50mph, and I go to speed up, but without dropping into a passing gear, the entire truck hesitates as if the ignition cut off and right back on.

As mentioned before, I was throwing at passenger side Cat code, but it kind of went away. I reset it in an attempt to get through inspections and after the third reset, it never came back.

Any ideas?

the coil , the missfiring, did you r/r plug, or clean, or inspect. also this miss firing could cause the cat on that side to get damaged like by overheating and damaging the cat as this is the purpose of cat to burn off unburned fuel........

[Brawndo]

I pulled all 8 plugs right before I changed coil. No 1 plug showed any more than another. All were gapped right on .60, plugs (AC delco platinum) and wires were done about 3000 miles ago. Also have changed fuel filter. It first was acting like the EGR valve was faulty, so I unhooked the wiring from it to leave the valve wide open, and it still hicupped.

At low rpms, engine runs great. Rev in park or neutral, engine sounds great, it's just when it's under a load that this hesitation comes in at lower rpms.

I know that the cat is bad. The guy who is going to install new one confirmed that. Could the faulty cat be causing this hesitation?

I apologize for not having the vocab. to describe more accurately.

Thanks,
B

[J-Ri]

A plugged cat will usually cause problems at high RPM because there is too much backpressure. Before you go replacing the cats, make sure the post-cat sensor is good. In almost 3 years as a professional technician, I have only seen one bad cat when there's a "catalyst inefficiency" code. Every other time it was a bad sensor.

[Brawndo]

Ok, so I got it to throw a code finally. Tonight on my way home from work, I finally got code, P0171B - Fuel Trim System 1 Bank Lean, Don't quote me on the wording.

Basically, it is misfiring. But it's not starting until it gets up to temp, like I said before, 200-210 range. Once it gets there, the misfiring becomes very imminent. I can rule out injectors since increased rpm will actually smooth things out.

Any ideas, I am going to research this code. Does anyone know which side, Driver or passenger is bank 1? I think it's driver, but I'm not sure.

Thanks again.

Billy

[j cAT]

Originally Posted by Brawndo

Ok, so I got it to throw a code finally. Tonight on my way home from work, I finally got code, P0171B - Fuel Trim System 1 Bank Lean, Don't quote me on the wording.

Basically, it is misfiring. But it's not starting until it gets up to temp, like I said before, 200-210 range. Once it gets there, the misfiring becomes very imminent. I can rule out injectors since increased rpm will actually smooth things out.

Any ideas, I am going to research this code. Does anyone know which side, Driver or passenger is bank 1? I think it's driver, but I'm not sure.

Thanks again.

Billy

bank 1 is the drivers side and if this was the side with the bad coil all makes sense. that cat usually gets damaged if it works all the time removing excessive amounts of unburned gases......replace both upsteam o2 sensors when the defective cat is replaced.......

[Brawndo]

That's what i thought, but the bad cat is on the other side.

It's gonna be a long saturday...

Thanks for all the help, I know I'm being a PITA, but I need to pick everyone's brain.

[itchysores]

Originally Posted by Brawndo

That's what i thought, but the bad cat is on the other side.

It's gonna be a long saturday...

Thanks for all the help, I know I'm being a PITA, but I need to pick everyone's brain.

Brawndo, were you ever able to solve this issue? I'm experiencing the very same thing with my 2000 Silverado 5.3L.

Thanks!

[mdharmon]

Had same problem that increasingly got worse until the truck wouldn't even start. It was the fuel pump. There was just enough volume of fuel to run the motor but when you accelerate then the volume wasn't there, the pressure drops and the engine sputters. I removed the fuel tank and pump in under 45 minutes. Reassembly was about an hour. The fuel pump was under $200 from local parts chain.