Hi everyone I am having trouble with my truck not running right. It pings very badly whenever accelerating and has no power under load. The pinging I didnt notice until lately but the power loss started months ago gradually and out of nowhere. So I did just about everything that I could think of. I replaced spark plugs with good Champions. I replaced the wires with MSD 8.5mm wires. I replaced the cap and rotor. I tried running Seafoam and other fuel treatments. I tried higher octance fuel and fuel from different gas stations. I checked the compression in all cylinders and they are all above 155 psi. I replaced the intake and plenum gaskets with Felpro. I tried capping the vacuum ports. I replaced the MAP sensor. The only thing that I didnt do was replace the O2 sensors but I wouldnt think they would cause it to run this badly. It doesnt throw codes for either O2 sensor or anything else. I am at a loss for why out of nowhere the truck has no power under a load or why it hesitates. And what I mean by hesitates it when I start out from a stop it starts moving but right away the RPMs drop a couple hundred then pick right back up. Both these problems are when the engine is either cold or hot. And when I started noticing power loss over a few months I do remember that for the first minute or two after a cold start it would run great with plenty of power but then start running badly again. I remember that the truck used to spin the right tire every time I made a right turn from a stop but now it doesnt even have enough power to do that. It is lifted with 37s and 4.10 gears but it used to never have a problem spinning them. Even before I lowered the gears it had more power than it does now. This is my everyday driver and it is so frusterating not to be able to figure out what is going on. Please someone help!

 

Some of your symptoms sound a lot like a failing O2 sensor. Easy test though, simply disconnect the front O2 sensor, go for a drive... see if it's any better. If it is, put in a new sensor. (NTK, or Denso please, skip bosch) If it still seems down on power, remove the front O2 sensor from the exhaust, go for a drive. (it'll be a little loud.... leave the sensor disconnected as well.) If it runs better, that points to a clogged cat.

 

Yeah I have tried disconnecting the O2 sensors. Doesnt make a difference. I havent tried running it without the O2 in though. The cat could be clogged but wouldnt I smell it or notice a different sound from the exhaust? Oh and by the way it is true dual exhaust that the previous owner had installed. I can tell by hitting both cats that one is gutted. The O2 sensors are on the pipe with that cat that is not gutted though.

 

Pull the sensor, and see what happens. Take it from there.