Need a little help with p0300

[cpt7868]

Hi guys, first time poster, long time reader & creeper

Here is the issue the dreaded p0300 random misfire no other codes on my 1999 Yukon SLT 5.7 vortec 156000m

Here is what I have done:

1. New cats 4 months ago; 4 new o2 sensors
2. New muffler
3. New wires, plugs, cap, rotor, coil (AC Delco parts)
4. Clean and inspected EGR valve (it rattles)
5. Disconnected battery for 10 min, (told resets computer)
6. Changed fuel filter
7. Upgraded the spider injectors to multi port spider injector
8. All new gaskets for upper intake
9. Disconnected plug wires one at a time (no noticeable difference)
10. Vacuum pressure holds steady at 19.5
11. Dry compression test all within 3 % of 165psi
12. Removed the upstream O2 sensors thinking cats were plugged (no change)

I clear the code and with-in 2 min its back, running out of options. Any other help or direction would be appreciated. Never had any major issues with the truck since I bought it new, I would like to hand it down to 16 y/o daughter, once the bugs are gone

 

[SunlitComet]

You need to get the misfire history read from the pcm to determine exactly what cylinder is doing it. That should be your first priority.

 

[cpt7868]

Thanks for the reply. I have been thinking of upgrading to some sort of scan tool instead of my code reader. In one of your earlier posts was a link to a scan tool, I can't find it anymore. Is there any one type you recommend?( not a big fan of my innova's repair solutions). Thanks again

 

[SunlitComet]

I use a pc-based program called scanXL with a plug in interface adapter. I will be moving to efilive's system soon tho as it has bi-directional control features that the ScanXL does not. In either case make sure you have a good fast laptop or it may reduce the data sampling rate as you try to log a busload of pids at once. Either of them will get you misfire history tho.

 

[nimrod.sixty9]

I use a pc-based program called scanXL with a plug in interface adapter. I will be moving to efilive's system soon tho as it has bi-directional control features that the ScanXL does not. In either case make sure you have a good fast laptop or it may reduce the data sampling rate as you try to log a busload of pids at once. Either of them will get you misfire history tho.

How do I do this in SXL? AS you know Im running through the same bit...

Well i got a freeze frame reading, not live i guess...

 

[SunlitComet]

you mean Scan xl? you want to select "data view" from the diagnostics tab. if you don't see it there you have to configure the pid's to be visible to you under "pig config" on the settings tab. then turn on record or monitor function on.