p0300 CODE

[supreme3940]

I HAVE A 1999 GMC YUKON 5.7 V8 WITH 179,00 MILES ON IT. THE TRUCK IS GARAGE KEPT AND RECENTLY IT BEGAN TO RUN ROUGH. I GAVE IT A FULL TUNE UP WITH THE PLUGS AND EVERYTHING BUT THE I AM GETTING LOW COMPRESSION ON THE #6 CYLINDER AND MY GAS NEEDLE BEGAN FLUCTUATING. ALSO, THE TEMP GAGE IS VERY LOW. ANY HELP WOULD BE APPRECIATED. THANKS

[east3021]

The fluctuating gas gauge is probably a cluster issue or sending unit problem. Neither would necessarily cause rough running.

The temperature gauge could also just be a cluster issue or bad temp sending unit. With a scanner, see what the coolant temperature sensor is reporting. Does the upper radiator hose get hot within, say, five minutes after a cold start?

What were all eight pressures on the compression test? Follow up with a wet test on the low cylinder to see what could be causing it.




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