2004 Chevy Silverado. Engine size = 5.3L v8. Warning lights: engine under powered (in odometer window). I shut off the truck and the problem went away but the check engine light stayed on and my dad said he believes it may be the oxygen sensors and if it isn't fixed asap it could wreck the catalytic converter. Question = hi i have a 2004 Chevy Silverado which i just purchased today i was on the highway driving and pulled off into a mall and my check engine light came on and the truck started miss firing and sputtering like it was going to stall in the odometer window it said engine under powered" and it wouldn't go over 2000 rpm or 30 km/hour after shutting the truck off and restarting the truck ran fine but dont want to leave it cause i have heard it can get real costly real fast if the oxygen sensors are gone,
Answer: It probably is not the oxygen sensors causing your issue. There is an electronically controlled throttle body on your truck that will usually cause this problem when it goes bad. It usually puts up a message like 'engine power reduced', not the 'engine under powered' like you state.
Either way, it set a trouble code and that is why the check engine light is on. You would need to get it checked out by a shop or someone with an appropriate scanner. If it has any throttle body codes, or TAC actuator codes, or throttle position, correlation, etc...you will need to replace the throttle body and throttle body gasket. The idle when then need to be relearned after replacement.
2000 Chevy K2500 5.7 Question = I have a 2000 K2500 with 174,000 miles. The truck runs bit rough in damp wet weather until well warmed up.I have it had the truck tuned up a couple of times over the years last tune up about 30,000 ago I am not getting any codes but it feels like a miss fire however the plugs appear to be in good shape. New PCV Valve,Air filter, 02 Sensors are original as is TPS switch. The truck is getting 10mpg at best around town. What should I do short of buying as new truck.
Answer: You could be getting a slight misfire from a bad coil assembly. They can arc around the metal casing or bracket, especially when damp out. A bad coil wire can do the same thing, as can a distributor cap and rotor that has condensation inside it from damp weather. I'd definitely lean towards an ignition problem, since those components are the most affected by weather and cold start conditions.
You might want to do another full tune up, including cap, rotor, wires, coil, plugs, etc. Also look for any vacuum leaks that may be causing a rough running condition. Sometimes intake gaskets suck air, throttle body gaskets, or loose and rotted vacuum lines too. Since it has a lot of miles, concentrate on wear and tear, and maintenance items, and that should help your problem.
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