I have a 03 silverado 6.0 swap truck was running right until few days ago I was driving it and it started backfiring while giving it gas.. now it idles terrible like it's misfiring.. I took of the intake tube and the throttle body is looks like is wet but it's gas.. what would that problem be?

 

Any codes?

Have the log file from a tuner handy?

Have a scan tool to diag the problem and watch sensors?

It's way too hard to guess over a computer when I can't see if something is wrong through a data log/scanner. Could be tons of things. Check for vacuum leaks, fuel leaks at the injectors, bad MAF, bad MAP, bad o2 sensors.

 

No codes no cel light on but it idles like crap.. the mass airflow sensor also smells like gas.. has new plugs, wires, new cats o2sensors..no vacuum leaks

 

Check/clean all grounds.

 

No fuel injector leak, clean the maf, it idled better but still smells like gas out the exhaust

 

If it was running fine before the new plugs, wires, cats, & o2 sensors then one of the four is your culprit. My bet is on the plugs and/or wires - sounds like a cracked plug or bad/loose wire. Could always be a bad coil as well - you'll find it :>)

 

When I turned it own it smells like a 2stroke engine, like a wheat eater.. I'm so frustrated with this truck

 

No it was running better but in the highway it would backfire when I would accelerate.. they told me it was the cats so I put lt headers on it, new o2s and wires.. ran fine for like 2 weeks and all of the sudden it did it again and now it's worse.. before it had the cel p0300 code random misfire.. but it didn't smell like a 2stroke engine.. now I don't have no cel on.. doesn't throw any codea

 

Did you rule out a bad Coil? They can work intermittently when failing. Just remove plug wires one at a time & check for spark. Also, if you didn't remove the plugs when you installed the headers you could have cracked the ceramic on one if you clipped it with the header. Happened to me when I installed my LTs.