I have a 98k1500. In january had a mechanic install a New Jasper engine, oil cooler, plugs, wires, cap, rotor, cam and crank sensors, air and fuel filters, belts, hoses. In march my truck had a bad miss at idle hard to start also a p0300 code, so I had him install a dist, a used computer and replace the fuel reg and spider. Now 2 weeks laterI have a slight miss but you can really feel it at 50+ mph. The truck surges, kinda jerks and I got a p0300 again. Any thoughts? I'm so lost and so broke now. $6000 in 4 months. I'm ready to take the bridge.

 

could be plugged cats. I had a previous car do this exact same thing. I removed the cats and it came to life.

 

WoW, give me $6000 and I would just replace your spark plug wires because they are probably arcing or in touching the exhaust manifold grounding it out. Check the wires for melted or burned rubber on the housing.

 

I know the first thing I would do is check the comp. I put a Jasper long block in for a customer years ago and within a week it had a picture window in the block. They replaced it with a short block that had a score in one cyl you could have laid a tooth pick in. They may be better now.

 

I had a P0300 code come up on my '08 Chevy Cobalt last week. It seemed to have an intermitent miss to it and then the light came on it went into the "engine pwr reduced" mode. The dealer replaced the throttle body and so far so good. Thanks, Steven

 

Happy your cobalt is fixed! p0300 can drive ya nuts! In my case my mechanic is going to re~flash my computer next week he thinks thats my prob. He just put a used computer in and didn't flash it to my truck and the gear ratio may be different. I'm crossin my fingers.