slowZ71

It crank strait up, idled fine. Light tap of throttle made it rev fast.

After the first break in and cool down, it has been throwing miss fire codes...

When the code is cleared it starts running better (shouldn't matter though.) And 1/4 throttle is about the same as few throttle. We put ARP stud grease on the the plugs pretty thick and was wondering if it wasn't getting good contact with block, or cause a/f and timing is off a little?

Can't get in touch with my tuner. It has fattened itself up so it'll idle, soo it could be getting a little too rich at idle?

5.3l, 220/224, iridium plugs, long tubes, and ory, head work, tune, cai, etc

terravast4

iTrader: (25)

maybe the knock sensors need to be adjusted in the tune

GMCtrk

iTrader: (27)

The exhaust reversion caused by the cam tricks the pcm into thinking the engine is misfiring. You need to have your tuner alter the tune for it. Basically I had the same problem and solved it by decreasing the misfire sensitivity below 1500 rpms

terravast4

iTrader: (25)

were you seeing a misfire at cold start-up?

slowZ71

umm... not cold start up. Just like after you have drove it a while. Once it acts up, you cant even crank the thing!

I got a scanner and it shows timing all above 10 deg. 25 full throttle, 3x's cruising, and 30-40 coasting. It has thrown the code about 10 times in one day.