P0301

[Kelsda]

Hi, all
Looking for information on the dreaded P0301 misfire cylinder 1 swapped out plugs and wires not new ones played the old shell game no change still P0301 new cap and rotor still same code 1996 yukon 5.7 vortec motor 115,000 miles friend came over with an expensive scan tool told me o2 sensors working but did not show misfire P0301 any suggestions would be greatly appreciated read something else about distributor gear possibly worn out how much play does a rotor have ? The more I read the worse it is to figure out May Day MayDay

 

[liquify33]

How does it run? Distributor gear at 115k miles seems highly unlikely to me. Have you done the spider injector swap yet?

I’ve had a 0305 lately and ran a can of Seafoam in a nearly empty tank and it went from better to gone in under 50 miles.


And don’t toss that distributor out.

 

[Kelsda]

How does it run? Distributor gear at 115k miles seems highly unlikely to me. Have you done the spider injector swap yet?

I’ve had a 0305 lately and ran a can of Seafoam in a nearly empty tank and it went from better to gone in under 50 miles.


And don’t toss that distributor out.

Low rpms stumbles, really rough highway speed seems fine worried about killing cats driving, did not do spider upgrade yet I don’t think its leaking fuel no black smoke from what i read different codes for a bad spider like P0300 random misfire i will see if the manifold is leaking next. I will try the sea foam maybe carbon build up

 

[exp500]

Check for vacuum leaks around intake, seafoam/ berryman in gas tank. Check fuel pressure, check fuel trims/ misfire on all 8, maybe even cam retard offset (timing at zero) Torque app works for that. Usually ignition module just fails, but maybe its close. Same with coil. Do you have bright white/blue spark? Lastly are you loosing coolant? Coolant Clean?

 

[OR VietVet]

Basics. Compression test. Vacuum leak inspection. Suspect the spider though, common problem.

 

[liquify33]

Do you hear a ticking sound?

 

[Kelsda]

Checked compression 165 no leaks around intake possible coolant leak reservoir empty once again no visible leak

 

[OR VietVet]

What is the compression at the next cylinder, #3? Pressure test the cooling system and inspect for a leak. Look at the bottom of the water pump at the weep hole.

 

[Kelsda]

I did see a wet area on the right side and rear of motor can’t really see where it is coming from I was looking around with a mirror I’ll do a Preasure test seems like oil but possibly antifreeze

 

[OR VietVet]

I did see a wet area on the right side and rear of motor can’t really see where it is coming from I was looking around with a mirror I’ll do a Preasure test seems like oil but possibly antifreeze

Heater hoses and this is in that area: https://www.rockauto.com/en/moreinfo.php?pk=84579&cc=1166431&jsn=2248

Make sure to clean off that wet area before pressure test and leave the pressure tester on there at pressure and watch for pressure drop. That weep hole at water pump can be tricky but if is leaking should leave a corrosive stain/trail.