PO306 Code (1 Viewer)

[Cass007]

Trying to finish up the baselining on the cruiser and thought I was just about done, but now I have a PO306 code. Truck is running rough at idle, but seems to be fine at rpm above 2k. It doesn't stall, but seems close. Also seems worse when the truck is started cold vs warm restarts. This started just before all this rain, so it was dry when it began and I haven't been out puddle hopping.

I have plugs, wires, cap and rotor to go on, but threads seem to indicate this not being the issue. However the same threads seem to indicate the reverse symptoms of what I'm seeing (less power on highway and fine at idle).

I ran the gas pretty low, like solid fuel light low, just before this started. Possible dirty fuel sock or filter? I will get to the tune up stuff tomorrow hopefully, but I'm not really confident it will solve this issue. Open to thoughts on what to look at next.

 

[dci blair]

P0306 is a fault for misfire on cyl 6. Start by inspecting the plugs/wires. look for arcing in the wires (little lightnig bolts best seen in the dark/low light) then pull number 6 plug. Pull number 5 plug and compare. Could be anything from a bad wire to internal motor issues or even a fuel injector. Start with the basics and go from there.

 

[Crusha]

Could be anything from a bad wire to internal motor issues or even a fuel injector

...or head gasket

 

[dci blair]

...or head gasket

I was trying to give some hope lol.

 

[jamarquardt22]

I want spark plug pics. Labled and in order.

 

[Cass007]

...or head gasket

Do NOT speak of what shall not be named ... I saw that in the research threads as well. Oil is fresh and very clean still on the dipstick. Coolant still looks like s***, but still getting the sand like stop leak crap the PO had in it. Temps on the scan gauge are always good. No signs of leaks on the garage floor or the trans tunnel.

Andy - will do pics and labeling when I can do the maint. Huge projects at work this past 2 weeks that come to a head next Tuesday. Will def have time after that if not before. I was hoping to get this done today, but a family member had their basement flood and I've been helping with that for the past couple of days.

 

[Crusha]

Do NOT speak of what shall not be named

Definitely NOT the head gasket

My vote is plug wire, especially if they are aftermarket.

When I was a tech, I used to mist the wires with water from a spray bottle, and touch each wire. I'm not kidding. It was pretty standard practice with a handful of us at that shop. You get used to the shock. I don't know if I would want to do that NOW, but back then, every minute counted. It was a flat rate shop.

 

[KGBruce]

Kinda like testing a transistor battery with your tongue instead of finding the multi-meter

 

[Crusha]

Kinda like testing a transistor battery with your tongue instead of finding the multi-meter

I STILL do this!

 

[jonheld]

Inspect the wiring harness that runs next to the EGR pipe. On older trucks, the retaining clip becomes brittle and cracks. This allows the wire bundle to make contact with the hot EGR pipe. Insulation melts, wires short, dogs and cats living together, mass hysteria.

 

[KGBruce]

Something like that happened to me about 15 years ago in my '93 80 series which I bought new in '93. I was coming home from the Phila airport around 1:00 a.m. Traveling west on Rt 322 (where it got real dark) my headlights went out...nothing. Freaked me out so I pulled to the side of the road, no other traffic. Couldn't figure it out (that's not saying much) so the only thing I could do was grab the BIG Maglite flashlight I kept in the truck. Flicked it on, stuck it out the window and drove up Rt 322 to Rte 1 to Rte 202 all the way home to Downingown just using a flashlight! Nobody noticed the guy in the dark truck flicking the flashlight around. Took it to the dealer the next day and they said "damaged wiring harness".

 

[dci blair]

@jonheld kudos to the ghostbusters reference

 

[jonheld]

@jonheld kudos to the ghostbusters reference

I'm here to help.

 

[jamarquardt22]

@jonheld kudos to the ghostbusters reference

Ah your right! I had been thinking it was from Jurassic park or Independence day.

 

[brian]

I'm here to help.

Now tell him about the twinkie.

 

[Cass007]

Starting with 6 at left to 1 at right and the rotor.

6 - 5 - 4 in that order ... 6 looks awful dry

6- 5 - 4 tops ... nothing unusual

Plug 5 top was dirty likely because the protective boot on the top that meets the valve cover was partially torn off ... thanks to the PO.

 

[Cass007]

3 - 2- 1 ... 3 looks great, 2 looks like crap

3 - 2- 1 ... again all look just fine to me

rotor looks a little beat, cap had normal wear

None of the wires had discoloration that I would expect from arcing. All of the plugs looks lean to me, thoughts?

I swapped everything out and was happy to see the truck run smoothly. Took it for a 5 mile test loop with air on and off ... no issues. pull it in the garage, put in park and turn off AC and I can hear it begin to occasionally stumble. It only happens in Park and only with the AC off. In gear with my foot on the brake at a full stop it holds between 605-612rpn at idle. Nice and smooth with AC on as well.

 

[jamarquardt22]

That's a start I hope you found it.