RRBigDan1

Please bare with me:

About a year ago my 04' 2500HD developed a small exhaust leak. I thought it was just a gasket but to my great surprise I was told it was a broken exhaust manifold bolt. I continued driving and progresively the noise got louder and louder. For the passed few months I started stock pilling parts (water pump, alternator, belts, injectors, coils, gaskets, etc). Instead of attempting to drill out the boken or sending the heads out to a machine shop I went to eBay and found a salvage yard that wanted only $300 for both heads (remanifactured).

So I started blewing the engine apart, I replaced the head gaskets, bought new headbolts...you know all the good stuff I re-installed the heads and torqued them down, along with the rocker arms.

Basically the install went perfectly. I also replaced the stock mechanical power fan with a pair of electrical fans.

I reinstalled the battery and put the key in the ignition...before the first start up I pulled the fuse for the ignition and turned the engine over several times to prevent a dry oil start since the truck has been parked for a while. When I put the fuse back in and turned the engine it fired on first turn.

After busning off some oil on exhaust pipe is sounded great, it didn't shake, sounded great...no exhaust leaks...basically I surpised even myself how good it sounded and how good it was running. I took it for a spin and minute after minute it started feeling like the engine was losing power. As I was pulling into my driveway the engine light started blinking...I've never seen it blink but I assumed it was something that needed immediate looking into.

So far the only code that has been coming up is the P0300. multiple random misfire.

I've spent all day today diagnosing this and trying to figure out what could it be...I pulled all the pugs, disconnected injectors...etc. had one plug that was wet, tracked it to a faulty coil and one injector...I hopped this was it...but after this it still threw the same code P0300.

Has anyone had this issue? I don't know what else to do...tomorrow I will go to my local part store and buy a exhaust pressure gauge. I hope that when I test the back pressure of the catalytic converter that I find out that it has collapsed and is blocking the exhaust gases...because I've got nothing else to think it could be...

PLEASE HELP!

nkh34

check the rotor and distributer cap this might be caused from cross fire check for cracks and carbon tracks.

RRBigDan1

It's a 2004...I don't believer that my truck is equipped with a distributor...? It's a 6.0L...LS based engine, I think it uses a crank positioning sensor for ignition.

country_09

Check the o2 sensors while you're at it. They can cause some crazy things to happen

RRBigDan1

Yesterday I checked the back pressure of the exhaust before and after each cat and its normal. O2's have been replaced.

Someone told me to check/relearn/replace the crank possitioning sensor. Where would I locate this sensor on a 6.0L?

Thanks,
Dan

country_09

I believe it's under the starter, but don't quite remember on that one