Hey everyone. first I'm glad to have found this place, I love my truck and am not afraid to work on it myself

1st problem, the truck recently has developed a loss in power,seems I have to give it more throttle, but the sound has changed , more gutteral low toned engine sound, like it's laboring. it also has a wierd squeak or squeal coming from cylinder # 8, I unplugged the coil wire and it gets louder so I know it's that # 8, also I swapped another coil but still the same. once it warms up it goes away but still doesn't have the power. Now... the engine code light comes on.. flashes as a missfire, so I am assuming that may be a big part of the problem. could it be-plug, lifter sticking, rocker arm? or Cat plugging up??

Problem # 2 I cannot scan the truck with my scanner.... it won't power up.. I have read that the odb2 may share with cig lighter the power.
I have 2 power plugs, one has power the other doesn't(the one closer to the steering wheel) is this the one that is shared? I cannot find a bad fuse although I have not gone through every one. anyone else have these problems???

6.0 liter 2003 gmc HD crew cab about 110'000 miles
running synthetic mobile 1 oil, getting regular unleaded fuel
no mods to the engine(Yet)

anyone help? suggestions?

Jim

 

Update

I pulled a few plugs on that side, they are not fouled, which I hope means no internal problems such as valves or broken ring.... I am going to change all the plugs and wires(probably a good idea anyway)

Update #2 no change

still looking for suggestions or your experiences

 

Sounds like a busted valve spring on that cylinder. Take the valve covers off and inspect. The obd plug does share power with the cig lighter. Someone else had the same problem on this forum. I suggested to disconnect the cig lighter power and see if it worked. Which would mean the lighter is shorting out.

 

would the plug foul up? I changed them all and they all looked the same. someone else suggested a broken ring maybe... ughhh how can that be checked.

if I take off the valve cover(which doesn't seem like the old ones from days past)what should I look for? turn the engine over and watch the valve movement?

 

You should be able to see it busted. Might even wiggle it. Im not sure it is. But I read a story on a forum how a guy had replaced everything he could to fix the stuttering miss. When he scanned it, it kept saying cylinder misfire. It turned out to be a broken spring. A 30 dollar part instead he spent 1600 to try and guess.

 

Also check compression on that cylinder. That will for sure tell you the problem.

 

yeah, it got worse today driving to work.... it's about done. loss of power. so I will take some today and do some tests first like get the ODB2 powered up and also pull the valve cover then also do a compression test on the cylinder, BEFORE I take it to someone to diagnose further.

If I have to,I have a lead on a few engines with less than 58,000 miles for around $1800 with 6mos warranty does that sound fair priced?

 

Yeah that sounds pretty good. Then keep the other one and slowly rebuild it. But I hope you will be able to fix yours.

 

Good news, looks like one of my first thoughts of a Cat plugged up is partially true.... U sent it in for diagnostics toay, They just called and said the "Resonator" before the cat was plugged up.

So as I thought the squealing was actually a high pitched loud whistle coming out of a small exhaust manifold leak at cyl #8 from Backpressure and as it warmed up and the manifold expanded the leak got smaller. thus the noise going away. but the missfire and power loss was from no good flow in that side of the engine exhaust. SWEET

$442 for pipe, install and a fuel filter I am having them do.... Not bad I think... much better than a few grand.

Plus it got me to do a tune up to boot, so I'm in good shape
Thanks everyone for the help

 

Good deal bud!!!