GM ???, last resorts
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Posting Guru
Joined: Jun 2004
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From: just outside of Phila.
GM ???, last resorts
Alright all, I know, it's a GM question on a Ford board. Everyone's so helpful with everything else, I thought I'd give this a shot too.
My parents own a 1998
Chevy Tahoe with the 5.7. It's been nothing but trouble for them, and it's killing me watch them deal with it. Right now, it hesitates and makes a popping sound under the hood when the gas pedal is pressed any farther than 1/4 inch. Codes said a #4 misfire and O2 sensors (there are 4), both have been fixed, but to no avail. There are two new injectors in there (don't ask me why not 8, I got involved too late to stop them). The air filter is new, the fuel filter is new, and the fuel pump is new. It is not an exhaust backfire, but a muffled popping sound, almost sounds like an intake thing.
Now for the mystery...it only does it with a half a tank of gas or more. My dad told me this and I thought he might've been nuts. He swore up and down that it was better with a half a tank or less. I finally started taking it, and driving it more myself. The old man was right, it's almost exact. No more than 1/2 tank or the truck will dog.
What in the world does this mean?
My parents own a 1998
Chevy Tahoe with the 5.7. It's been nothing but trouble for them, and it's killing me watch them deal with it. Right now, it hesitates and makes a popping sound under the hood when the gas pedal is pressed any farther than 1/4 inch. Codes said a #4 misfire and O2 sensors (there are 4), both have been fixed, but to no avail. There are two new injectors in there (don't ask me why not 8, I got involved too late to stop them). The air filter is new, the fuel filter is new, and the fuel pump is new. It is not an exhaust backfire, but a muffled popping sound, almost sounds like an intake thing. Now for the mystery...it only does it with a half a tank of gas or more. My dad told me this and I thought he might've been nuts. He swore up and down that it was better with a half a tank or less. I finally started taking it, and driving it more myself. The old man was right, it's almost exact. No more than 1/2 tank or the truck will dog.What in the world does this mean?
Post Fiend
Joined: Feb 2003
Posts: 6,940
Likes: 2
From: Eastern WA
Backfiring out of the intake maybe? Have you tried pulling codes recently? Does it do it regardless of engine temp or just when cold? Have you run any fuel system dryer in it since last fall? Just a few thoughts.
Thread Starter
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Posting Guru
Joined: Jun 2004
Posts: 1,371
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From: just outside of Phila.
we pulled the codes about 2 weeks ago, changed all plugs for a cylinder 4 misfire, and replaced the O2 sensors. It does it cold or warm...that doesn't matter. It's the amount of gas in the tank...honest, 1/2 tank or less, and you'rer ok. Anymore, and it does it. Ran some seafoam in it about a month ago, through the gas tank.
There's also a place around me that claims to be able to do a full fuel system flush...I don't know how, I never heard of it until then.
Cats have been changed too.
There's also a place around me that claims to be able to do a full fuel system flush...I don't know how, I never heard of it until then.
Cats have been changed too.
Hotshot
Joined: Feb 2004
Posts: 11,697
Likes: 3
From: Marengo, Iowa
may seem simple and stupid, but it has happened on my mom's 02 Buick, but try the gas cap, the valve goes bad (apparently pretty easily) and messes up the signals or some thing like that. Basically, it builds a vacuum and then doesn't pump right. Otherwise, sounds like either a vacuum leak or possibly bad Throttle position sensor.
