Some of ya'll may remember me previously posting with the no shift issue... Well I broke down and spent 2,000 I didn't have on a rebuild. Got it back finally and it shifts like a brand new truck! In fact I was so happy I decided to tune 'er up...

Shouldn't a done that.

I threw plugs, wires, distro cap/wire, filters/etc and a seafoam treatment in it and now it has a dead miss. I've cleared codes and driven it multiple times it always comes back P0308, Cylinder 8. Re-gapped the plug multiple times. Followed the TSB for the coil wire routing, no change. Swapped the Cylinder 8 injector with the Cylinder 2 injector (And broke a f*cking O-Ring, so now it leaks gas too -_-) and STILL comes back P0308. Went and bought a compression tester JUST to test this - spent an hour doing all 8 cylinders - Every last one is between 110 and 115.

It's always had a minor misfire on Cylinder 8 but somehow after I tuned it up that cylinder is just dead... Funny thing is I'm not even 100% sure it's Cylinder 8, only going on what the code says. I had my GF powerbreak it while I pulled each plug wire and NONE of them caused a signifigant change in the motor...

I'm 9 hours into a 45 minute tune-up and completely out of ideas. Anyone have a clue?!

Thanks

 

its completely dead or still just giving misfire? if it's just misfire you might test your coil. If I remember right, they like to favor misfire on that cylinder

 

1. Have you tried a different spark plug in cyl 8 to eliminate the fact that the plug itself could be the issue?
After checking that...I'm with racefan...perhaps time for a new coil?


As my 5.9L engine has aged, despite maintaining it well it has been rough on coils these past 100k miles.


-C

 

might double check your new wire is good too if your saying its completely dead now

when you test it make sure its at room temp too. if it is bad, I recommend the dealership from my own experience

 

Little update... So I went out, pulled the plug again just for good measure and verified with my own eyes there is clear and strong spark at the plug. I went and got another can of sea-foam and did another treatment thinking maybe some carbon broke loose and got stuck... Well...

Test drove it after clearing codes, still stumbling all over itself. Took it on the highway, beat the ***** off of it with the CEL blinking at me the whole time.

got back...

P0300, p0301, p0306 and p0308.

So... Basically it's missing all over the place. Falling flat on its face while you're driving it.

Here's my latest idea... Could the first Sea-foam treatment have knocked enough built up crap loose to clog up the CAT?! Now that it's in my head I feel like the symptoms are pretty much in line with a clogged cat...

Obviously I'm going to look into this farther before I go hacking that state-mandated bull-S out, but... Whatta u guys think?

 

First off, easy on the sea-foam. Enough is enough.


If I were you at this point, I'd change my oil and filter and go buy a new coil. If that does not fix it and I were you, it would be going to a professional shop just for the "diagnostics" next.


BTW, Did you change out the rotor inside the distributor cap?...you never said.

 

Yeah, rotor too. I actually *was* a professional mechanic for the first 7 years of my adult life. Aside from their expensive electronic equipment I'm pretty much on par with em'... Why pay em $110/hour? lol

I'm going to change the coil out tomorrow... I mean hell, why not? Pretty sure it's original. If that doesn't work... Time to sawz-all the cat out unless anyone can think of an idea between now and tomorrow.

thanks for all your input so far everyone!

 

Take out the front O2 sensor from the exhaust. (physically remove it, not just disconnect it.) Go for a drive, any better?

 

Before hacking your exhaust apart...
Does it still rev up, or does it fall on its face as the rpms get up? You can also just take the front O2 sensor out of the hole and go for a quick drive to see if it feels better. It WILL be loud though.

 

yeah Im going to try that O2 sensor trick tomorrow. Still revs all the way up just runs like ****