P0302 Code and misfire - Not spark...What next

[sc-surfer]

Drove the van 80 miles out and back on the weekend on the freeway without issue. Ran fine and got decent MPGs. Parked it on Sunday and when I started it up yesterday it immediately fired off the P0302 code and has very rough idle. Miss continues throughout the RPM range.

Pulled the plug wire on #2 and idle does not change. Miss is very rhythmic (i.e. clearly one cylinder, not a random misfire.)

Good spark at plug wire #2

Pulled the #2 plug and it was wet and smelled of fuel so not fuel starved. Maybe flooded? Can the injection system over-fuel a cylinder?

Plugs, wires, cap, rotor all 2K old.
Oil changed 1K ago
277K miles - yep, a lot! but was running well, quiet engine, no clacks, ticks etc. Ran perfect until parked.

Thoughts on what it may be?

Things to check next??

Thanks all.

[sc-surfer]

After chasing down compression, Injectors etc... it turned out to be a bad plug wire. They were 1000mi old so was not my first thought. Oh well. Live and learn. At least an easy fix.

[LaGrasta]

i've been chasing similar, P0304. I swapped the dizzy two weeks ago, plugs and wires 20k ago. I already swapped the plug, no change. Thank you for your post, after reading this, I'll swap the wire.

[LaGrasta]

As I look back through past post, I've been chasing this same code for so many years. Tried so many things, not sure what to do next. I ignore it, but every two years California forces me to deal with it, to pass SMOG. Somehow I manage the Check Engine light to be off long enough to satisfy them.

[MountainManJoe]

I swapped the dizzy two weeks ago

Did you swap the whole dizzy, or just the cap?
Sometimes the teeth on the rotor wear out, and sometimes the dizzy just needs to be re-timed.
(sorry I can't remember the details. It's been so long since I've had to mess with a distributor)

Poor fuel pressure is also a common problem on these vans, as well as vacuum leaks.

A full OBD readout might provide some clues. (MAF, fuel trims, MAP, ignition retard etc.)

Also you can try some troubleshooting on this page:
https://carkiller.com/scottykilmer/qa/misfire-4/

[LaGrasta]

new OEM dizzy and fuel pump, both just swapped in the last 500 miles.

[MountainManJoe]

You need to go through the troubleshooting on the page I linked.
Since it's only misfiring on one cylinder, you can focus on just those components.

#1
Visually confirm good ignition. Pull out the spark plug, plug it in, and ground the body using a clip or just lay it on the engine block. Remove EFI fuse, and crank the starter. Make sure you get a fat juicy spark.
Look out for cracks or carbon tracing


#2
Do a cylinder compression test
You could have failed valves, piston rings, etc.


#2
Test the fuel injection system.
https://troubleshootmyvehicle.com/gm/4. ... injector-1

[LaGrasta]

thank you

[LaGrasta]

It has good spark, good plug, swapped plugs in fact, and the same. Wondering if it can be fuel injection. I upgraded the FI spider years ago. That being said, one injector feeds all cylinders, correct? How can a single injector affect a single cylinder? I guess if one of the nozzle are clogged. The thing is, I recently replaced the intake gasket and cleaned the spider, although it didn't even really need it. Plus, the code has been on prior to any of this.

I added Berryman's FI cleaner in the tank yesterday with my fill-up. Yeah, I'm just putting up hail-marys. lol.

[LaGrasta]

it was the fuel injection Spider, last swapped 80k ago.

[MountainManJoe]

That didn't last very long. How did it fail? Could there be something else causing premature failure?

[LaGrasta]

aftermarket, how long should they last?

[MountainManJoe]

the life of the engine you would hope. Mine was still going at 200k