Really weird misfire issue

[Dnytro]

Ok background on truck
1996 c1500, 2wd, 305 auto. purchased at 140k, currently has 167k, oil changes done on time, never had a issue until yesterday.

Was pulling a U-Haul trailer 6x12, and it shut off for a split second, dropped into 3rd gear and the check engine light starts flashing and then it shifts back to drive and engine starts missing And knocking, shaking. I’m 200 miles from civilization so since the knocking/shaking goes away In 3rd year i make the choice to keep going at about 50-60mph Get home and pull codes

P0102 - maf
P0300 - misfire
P0304 - cam position sensor

Weird thing #1
Cleared codes, p0102 instantly comes back so I assume maf has failed. Swap that, no change. Check fuses, engine i fuse is blown. Replace it with another 20amp fuse, blows instantly. Put a 30amp fuse in it, doesn’t blow, and p0102 goes away.

Weird thing #2 p0304 never comes back, drove another 100 miles, nothing. Oil pressure is good, gauge behaves exactly as it always has.

P0300 did come back, and I hear and feel it miss. Checked plugs with it running with a test light, no difference on any cylinder.
Don’t want to throw parts at it, but I’m thinking first order of business is cap and rotor?

 

[Dnytro]

You must be registered for see images attach

 

[east302]

If you’re blowing that fuse then you need to find the source of that short (and put the correct amp fuse back in). For 98, and presumably 96, that fuse feeds these systems:

You must be registered for see images attach

Might as well start at the connectors to the MAF sensor and cam position sensor, see if you spot any damaged pink wiring touching metal or an adjacent frayed wire. To rule out the actual sensors, disconnect the sensor, replace the 20A fuse and turn ignition on. If it pops again, then the disconnected component itself should not be the source of the short.

 

[Dnytro]

That diagram is really helpful, gonna get some more fuses and report back asap

 

[SUBURBAN5]

I would be suspicious behind the distributor since that's we're the cam sensor is. Hopefully it's a simple fix if the wires got hot or rubbed on a piece of metal

 

[PlayingWithTBI]

The 1st thing that came to mind is your O2 sensor(s) heating circuit which may be somewhat shorted, drawing more amps. That may allow a 30 Amp to keep from blowing. Just a guess...

 

[Macs Garage]

I had that fuse blow and drove me crazy, usually happened if it was wet out, but not always. Turned to be the O2 sensor wire was touching the front drive shaft and had worn the insulation off. Taped wire and zip ties it out of the way.

 

[Schurkey]

What are the misfire counts for each cylinder?

 

[Deadman walking]

Them vortec motors are known for eating distributor gears atleast on the V6. Had a crank sensor go bad on my S10 no engine codes pulled it hooked the multimeter up and it read infinite. Not good. Those caps are bad for jumping spark pathways. Vortec is bad for having slight miss throughout the driving range.

 

[Dnytro]

O2 sensor wires all good, maf wires good, camshaft position wires good, gotta run to oreillys to get more 20amp fuses to test.

Cap and rotor looked ok, no cracks or excessive build up that I could see.