Have a temperature sensitive CEL. If it's 40 or below, no cel and idles smooth. Springtime comes and misfire cylinder 1 pops upon start up. A little rough idle but smooths out after a couple minutes. Trifecta tuned to 25 psi and it pulls strong and runs smooth. If outside temp drops then the light goes off. GM tech's stumped. Had the top end gunk cleaning done but no change. Had a leak down test and all fine. Compression good. No leaks. Thoughts?

 

If I had any idea what the DTC code was I might be able to help. You are wasting time without the code.

 

X2 what CEL do you have?

 

P0300 AND P0301, random misfire and misfire cylinder 1. I changed all 4 spark plugs and swapped coil packs and the same codes came on. So I feel it must be a fuel injector or an electrical issue but I don't know why temp would play a factor.

 

Check coil pack wires , fuel injector wires it could be a loose pin. It could be a faulty O2 sensor , I would look at these first.

https://www.obd-codes.com/p0300

https://www.obd-codes.com/p0301

It could be an exhaust valve, have you considered a Seafoam soak and treatment?

 

P0300 does not mean "random misfire" it means "unidentified misfire". In other words: the computer hasn't figured out which cylinder yet, then comes the P0301.

 

Did that as well. My GM tech friend did that for me on the side. Let it sit forever and ran it through til the smoking stopped.

 

What do you mean fuel injector pin? I haven't had a good look at the fuel injectors and how the wiring runs to them.

 

The connections are weather pack, with pins in the connection, like this..




Simply push the wire in a bit to ensure it’s seated in the connection

 

I'm thinking about drip irrigation. The emitter at the end of the line is often the first one to clog up. Sediment and impurities flow to the end, and collect there.

Unless I'm mistaken, cylinder #1 is at the end of the fuel rail. I see more P0301 on SS than any other P030x. Does this theory sound logical?