The infamous P0306!!!!
 

So, now that I have replaced just about every sensor, pump and injector on this vehicle, I'm now getting this P0306 error code. I have a new coil, cap, rotor, plugs and wires (all AC Delco except the wires, they are Autolite Professionals recommended by the Captain).

The error comes and goes along with a slightly rough idle while it's in drive.

Oh, and I just recently replaced the air charge temperature sensor because I was getting a P0113 error code as well. Well, I'm still getting a CEL for that one too.

The only thing I haven't checked is for a vacuum leak or cylinder compression.

Could these two some how be related?

The last time I checked my mileage I recorded 18.9 mpg (this was after installing new injectors and a fuel pump).

check #6 spark plug wire. got hot on exhaust and is grounding. intake gasket causing a vacuum leak. could be quite a few things...
:icon_twocents:

Changed out spark plug and wire looks good. Re-torqued the intake manifold bolts just to make sure there was no vacuum leak. I'm at a lost.

Anything else?

Retorqing the bolt probably wouldn't fix a leaking intake gasket. Compression test?

The reason I re-torqued the bolts because I just recently replaced the fuel injector assembly and I wanted to be sure I didn't over look one of the bolts.

I did find a small vacuum leak at the PCV elbow. After replacing it, the idle smoothed out a bit. Now, I'll reset the CEL to see what happens next. If this isn't the problem, I guess a compression test will be my next course of action.

oh, ok. were you into it far enough that you had the whole intake manifold off? the lower intake manifold gasket is right at the head and can be problematic is why i ask.

When did the misfire and P0306 start showing up? Was it just after doing work to it? What was replaced before it started missing?

Hey Captain!

Well, I replaced the injectors and fuel pump about two weeks ago. Everything was running great until the truck over heated lasted weekend.

By the time my wife was able to pull it off the road, the thermostat read 260! The upper radiator hose gave out (looked original) so I replaced it and the radiator (found a small leak). Since then, it's been idling rough, again and I think I know why...

I just came in from checking the compression for each cylinder and I just about threw a wrench at the garage when I came to number 6. All of the cylinders read somewhere between 148 and 151 with the exception of cylinder 6. It said 100 - twice.

So, I'm at a point now where I think I'm going to count my blessings and get rid of the vehicle.

But, if by chance a buddy is willing to help me work on it, can cylinder 6 be re rung from the bottom side? Or, do you have to pull the motor to do something like this?

Did the hose & radiator blow and then overheat? Or did it overheat and THEN blow the hose & radiator? I know.... it's hard to tell. Did you notice any coolant leaks before it overheated?

If a head gasket sprouts a leak into a coolant passage, you end up with compression pressure entering the cooling system... hoses and radiators are not designed to handle that kind of pressure and POOF, they blow out. If you fill the cooling system and put the radiator cap back on tightly, does the upper radiator hose pressurize immediately when the engine is running? Like to the point of being rock hard? Any white smoke from the tail pipe?

She noticed smoke first, then I saw the temperature gauge sky rocket.

The old hose was really worn around the end where it connected to the radiator (the clamp couldn't hold it on very tight) and the radiator itself had a small piece of plastic broken off (that's why I bought a new one).

No, I never really noticed a coolant leak before the vehicle overheated.

Okay, I just cranked over the engine to check the upper hose and it's still soft. And no, there is no white smoke coming from the tailpipe.

I also just ran the compression test on cylinder 6 again, about ten minutes ago, but I added about a table spoon of oil into the cylinder. The readings came up 120 is stead of 90 like the first time.

Come to think of it, the truck does run smoothly in the mornings or at least until the engine is completely warmed up. Does this have something to do with the oils viscosity?