another p0300 question

[Hummeron37s]

I agree a better scanner will help but why not buy a programmer instead of a scan tool. My Diablo Predator help me to diagnosis alot of codes,, besides checking and clearing codes it has live feed. It also a programmer and corrects tire sizes, changes shifts point, etc...It was about $350 great all around investment.
My P0300 code was a clogged cat which I replaced both with Magnaflow high flow cats that I got on amazon.com for $75 a piece and just had to cut the old ones out and weld the new ones in.
What year and how many miles on your Hummer.

[HMH2SUT]

xotik
i havent done anything yet except clean the maf sensor road side and check to make sure plugs wires tight.The truck was cold it had been sitting for a week. The smoke was white, only did it once, never before or since... Im not gonna get a chance to do anything till im off this weekend. im gonna make a list see what i can get done in two days . Im really over due for some maintenance, I change my fluids more then needed oil, trans, diffs, coolant etc... but i havent touched the motor other then changing a thermostat. KNock on wood till now I havent had any major issues.

Tech, on37s.
Im gonna pick up something better for sure. i think i pad $50 for my scanner... I can get the magnaflow cats at autozone near me for $80 thats not bad so im gonna throw 2 of them on if I get time this weekend.
My SUT is an 05 with 120k

[HMH2SUT]

small update... took my sut to the chevy dealer near bye to get it scanned. they said it is misfiring on numbers 2,7. and that 7 seemed to be the worst.They recommened a leak down test to check my valves... i understand a valve could cause some of my issues. But what are the odds of valves going in both heads same time? I left while the scan was still free...

so has anyone had a similar problem?

[HUMTECH]

I would pull the driver side fuel rail and check for water. It will pool towards the back and cause a number 7 misfire. Number 2 may be showing misfire counts due to 7 misfiring and not actually misfiring. If no water is present remove the injector and inspect the inlet screen for rust or contamination plugging the injector.

[HUMTECH]

If you had a scanner with live data you could swap ign coil, plug and wire with other cylinders to see if the misfire follows any of those parts.

[HMH2SUT]

thanks tech ill check that out tomorrow see what happens. i had heard that number 7 is a collection point... is it possible number 2 has the same issue? they are at opposite corners i believe if im not completely brain dead.

[HUMTECH]

#2 is likely just showing misfire counts cause it follows 7 in the firing order. would concentate on 7 and see if that fixes it first. Especially cause it is showing fewer misfire counts