I have a 1999 Camaro Z28 with a 6 speed along with a Hot Cam, LS6 intake, Longtubes and Y-Pipe through a LM1, and a set of 2001 injectors. Extremely mild. I feel that to properly explain my problem I need to fill ya’ll in on the story of the car. It originally spun a bearing before I got it and the intake pushrod on cylinder 3 was broken clean in half as well. I pulled the motor and had the bottom end rebuilt. I then removed the intake valve on the head where cylinder number 3 was located because it was caked in carbon and cleaned it, along with the head where the head and valve meet. After that, I cleaned the heads and put in new valve springs and valve stem seals (all done to the correct specifications in my manual). The motor was reassembled and put back in and my cousin has been tinkering with the tune with HPTuners. We put in fresh plugs, fresh wires, and a new fuel filter and fired her up. She drove decent, but we noticed a slight misfire and a P0300 code (along with a sporadic P0121 code). I checked all the plugs and noticed there was some oil on the plug in cylinder number 3. I cleaned it up and we just put it all back together and advanced the timing a bit along with a few other small things (my cousin would have to chime in on what else was done). I’ve driven it around 800 miles and it still has a slight misfire and a bit of a rough idle. When it’s been off for a long time the car fires right up and finds idle, if it’s been started in the last couple of hours then it’ll almost die and then struggle to find idle. Sometimes when I come to a stop and push the clutch in it will do the same thing, want to die and then struggle back to idle. Also, when I’m accelerating it seems to hesitate right after I switch into a different gear. I’ll put it into gear and press on the gas and it’s like it hasn’t registered yet and there is a pause, almost like the clutch hasn’t engaged the transmission yet (I’ve had a 6-speed 93 Z28 with a slipping clutch and it felt much different) and then it just takes off. When I shift to the next gear it does the same thing. It’s still throwing codes as well. I’m getting the code P0300 still along with P0121 every now and then (it doesn’t register all the time, just every three or four days it will throw a 121). Plug number three still has a bit of oil on it but the oil level is not going down any, it’s still at the same level as it’s always been. Anyone have any ideas on the hesitation, rough warm start, oil on plug, and codes? Could the hesitation/rough start/codes be related the tune not being correct and the oil just a coincidence and maybe a bad valve stem seal?

 

My first guess would be that the valve stem seal was cut by the valve stem when you assembled it. I would use a cylinder leak down tester. That should tell where the oil is from.