budhayes3

iTrader: (19)

Good job Dan, congrats! Now get back to school and learn something...you younguns are our future!

fredkj3

iTrader: (1)

man glad you found it... crazy to think that open headers was causing all that trouble.. good to know... ha... i had a very similar issue.. when i put the cam in it would miss under load... and i had a broken spark plug.... glad you figured it out..

DV2000NJ

iTrader: (10)

After driving a bit more, it turns out that the misfire isn't COMPLETELY gone.

A couple times at idle, it came back. Once I started driving, it stopped missing, SES light went away, and when I cleared the code, it didn't come back for another 20 miles or so.

I'm thinking the CASE relearn may still need to be done, but if I get some time this week, I'll go over all of the plugs and see if any are cracked, but that really doesn't seem to be the case, since it's fine under load, and only occasionally misses at idle.

GMCtrk

iTrader: (27)

Notice any power difference

hobbesnmina2001

iTrader: (1)

I started getting ticking sound on the drivers side like an exhaust or lifter and got the p0357 which says #7 P0357 (Ignition Coil G Primary/Secondary Circuit Malfunction). I need to check it out, has anyone experienced this before?
Its a 2003 6.0 L Silverado ~76 thousand miles stock. I thought the stock lifters/rockers where pretty good usually?
My scanner does show the misfire count on #7 up.

hobbesnmina2001

iTrader: (1)

I think mine is a bad wire on #7. I took off #7, and #3 plugs and they did not look much different both clean and dry. Put on Ohm meter on both wires and they had similar resistance with # 7 moving a bit higher around 100 here and there.
I switched coils plugs and wires, cleared the code and restarted, the code and missfires moved to # 3. I switched the wires only back and it seems a little smoother but it did that before without doing anything to it. I will drive it to work and but I am thinking the code will move back to #7 and it will be the wire. Its the factory wires and plugs with ~76, 000 miles but close to 7 years old, harder on the wires. I will get a good set and put them on. The resistance was 595 with # 7 595-700 ohms. ~100 ohms is around 17% higher resistance over the lower ohm rate on both wires. Although I could not see a spark at night moving around that ticking sound might be a bad shielf somewhere on the wire. Today we drove it a little before the work and you could feel the hesitation miss come and go.
If it was the hydraulic rolller or rocker it would be consistent and this comes and goes.

FNGtotheLS2

it could be a vacum leak, i have the same problem on my lq9 swap into a firbird, got it tuned and found the leak, since then ok

hobbesnmina2001

iTrader: (1)

The miss fires moved over to #3 so I don't think its vacuum leak, although that thought had crossed my mind at first.
I switched the wires only back. It is still miss firing on #3. I am going to put a set of wires on it and if the miss still there will try a new plug, after that it can only be the coil.

hobbesnmina2001

iTrader: (1)

I put new MSD wires in today and the problem was solved. The new MSD's measured at `46 ohms vs ~595 plus for the old ones!
The plug was the original # 7 plug which did not look much different but must have had something because it was still miss firing just a little bit at first. As the engine warmed up and I goosed the gas a little back and forth the miss went away completely and its running like new, you could almost stand a nickel sideways on it!
I got new plugs but since the originals are working well and looking clean I will leave them in a while longer.