Bad Gas?

OUMike · February 5, 2005

Hey everyone,

More trouble with the ol' 94'. So..yesterday I go to fill up and it runs fine the rest of the evening, and early the next morning. Later that afternoon while I was on my way down to Mardi Gras for the Eric Johnson show, I noticed it acted like it wanted to die or something. I would jerk, like it wasn't getting enough fuel or something. It would only do this on acceleration, regaurdless of how hard. My concerns maybe that the transmission is on its way out, but it doesn't shift unusually and it doesn't do it all the time. It did it on the way to galveston for a few minutes, and then ran fine the rest of the way. It then did it again on the way, home pretty much the entire drive (about 30 miles). It ran ok at first this morning, but then started to do it again. Bad fuel is the only thing I can really think of. I'm at work this afternoon, but when I get off I was gonna go get an O2 sensor, and some throttle body cleaner. How many O2 sensors do these trucks have (1994 4.3L Silverado)? I just recently had my truck inspected and it did pass the emissions test BARELY. I am putting out a lot of hydrocarbons. I believe the legal limit is like 147 ppm, my truck showed 146 ppm.

The truck is loud. The muffler is about 3 years old, but I definatly think there is a leak or a hole somewhere up at the motor, maybe catalytic converter? How much would it cost to replace somehting like this? Could a poor exhaust system cause the motor to stumble at certain RPMs? I have noticed the drone in the cab has gotten louder each week. At this point, my little 4.3L sounds like a 454 or something. I woulda taken care of it earlier, but I've been waiting on income tax refund.

I bought the gas from Wal-mart, so I really can't see them selling poor gas, but I suppose its possible. Thanks for the help everyone, I am at a complete loss. I have no idea what to do. I feel like O2 and Throttle Body is a good start. The fuel pump is less than 2 months old, and the filter is maybe a year. PCV, plugs and wires are all about 2 years old. Those will probably be my next step. Could it just need a tune up?

Thanks again

99-2door · February 5, 2005

Check your cap and rotor bug.

That's what you get for buyng gas from the BEAST

mcreyaufmiller · February 5, 2005

Check your fuel pump, mine acted weird just before it stopped working.

redvett · February 5, 2005

Hey everyone,

More trouble with the ol' 94'. So..yesterday I go to fill up and it runs fine the rest of the evening, and early the next morning. Later that afternoon while I was on my way down to Mardi Gras for the Eric Johnson show, I noticed it acted like it wanted to die or something. I would jerk, like it wasn't getting enough fuel or something. It would only do this on acceleration, regaurdless of how hard. My concerns maybe that the transmission is on its way out, but it doesn't shift unusually and it doesn't do it all the time. It did it on the way to galveston for a few minutes, and then ran fine the rest of the way. It then did it again on the way, home pretty much the entire drive (about 30 miles). It ran ok at first this morning, but then started to do it again. Bad fuel is the only thing I can really think of. I'm at work this afternoon, but when I get off I was gonna go get an O2 sensor, and some throttle body cleaner. How many O2 sensors do these trucks have (1994 4.3L Silverado)? I just recently had my truck inspected and it did pass the emissions test BARELY. I am putting out a lot of hydrocarbons. I believe the legal limit is like 147 ppm, my truck showed 146 ppm.

The truck is loud. The muffler is about 3 years old, but I definatly think there is a leak or a hole somewhere up at the motor, maybe catalytic converter? How much would it cost to replace somehting like this? Could a poor exhaust system cause the motor to stumble at certain RPMs? I have noticed the drone in the cab has gotten louder each week. At this point, my little 4.3L sounds like a 454 or something. I woulda taken care of it earlier, but I've been waiting on income tax refund.

I bought the gas from Wal-mart, so I really can't see them selling poor gas, but I suppose its possible. Thanks for the help everyone, I am at a complete loss. I have no idea what to do. I feel like O2 and Throttle Body is a good start. The fuel pump is less than 2 months old, and the filter is maybe a year. PCV, plugs and wires are all about 2 years old. Those will probably be my next step. Could it just need a tune up?

Thanks again

<{POST_SNAPBACK}>

You mentioned an exhaust leak. Any exhaust leak between the engine and the O2 sensor will change the airfuel mixture. It will cause it to be too rich because of the extra air being sucked in past the o2 sensor. Fix the exhaust before you do anything. Also has the vehicle had a tuneup lately? How many miles are on the truck.

OUMike · February 6, 2005

Check your cap and rotor bug.

That's what you get for buyng gas from the BEAST

Check your fuel pump, mine acted weird just before it stopped working.

Both are brand new. Maybe two months old.

budhayes3 · February 6, 2005

Like redvett said, that exhaust leak is gonna cause false readings from the O2 sensor...it's gonna see the extra oxygen in the exhaust and the ECM is gonna richen the mixture to compensate. I'd repair that first before I went after anything else.

sjspor · February 7, 2005

I dunno.. this sounds like a vacuum leak or EGR valve sort of thing..

DernMooseAk · February 7, 2005

I had a suburban do that, it was sediment in the gas tank. The pick up foot in the tank would pick up the sediment after a few minutes of driving and start to clog the fuel line.

In the morning or after setting for awhile the sediment falls back to the bottom of the tank and will run normal for a while.

OUMike · February 7, 2005

Thanks everyone for the posts. It ended up bein' bad fuel. I went down to auto parts store and got some STP fuel treatment and cleaned the Throttle body. Afterwards I noticed it was a lot better, and this morning (24 hours later or so) the probably was pretty much non existant.

The exhaust leak is a speculation. I'm startin' to think there is no leak, but just a bad catalytic converter. I'm not getting poor fuel mileage and the only symptom is noise. Its just a lot louder than I feel it should be with stock parts.

Truck is a 94 with 182,600 miles. I had my last complete tune up about 2 years ago, so I think that'll be the next step.