2017 Yukon Denali stalls after refueling

jim Hay · #1 07-15-2019, 07:40 PM

My GMC was working fine until I added a half tank of alcohol free gas. Within five minutes it sputtered and stalled while idling. Yellow warning lights and traction lights lite up. Restarted but had to keep idle high to prevent stalling. Stumbled to my auto repair shop. Codes show misfires on cylinder six. Does this sound like clogged fuel injector from bad gas?

larryderouin · #2 07-16-2019, 10:55 AM

More likely a fouled plug. Pull the plug, and have the shop take a look. the insulator in the middle should be intact and a light brown color. Gap should be about .040" to .060" depending on Engine (its in the manual) . A cracked or broken insulator will cause the plug to misfire. REPLACE IT.

Smokin' Denali · #3 07-22-2019, 08:24 PM

my opinion.....too coincidental that it happened right after fill up. The alchohol gas didnt have long enough to be problem in even a NON compatible motor. Diagnostic will show a random cylinder even w a few misfiring, in my experiences. Change fuel filter. Bet theres WATER in it! But pilling thatb plug cant hurt either....

Alternate: My 2015 Yukon Denali (6.2L) recently did exact same thing!! Made a turn at light and it seemed like I was running on 3 cylinders! Had to rev very high to move to side of road even!! Onstar diagnosis requested immediately by me ( Blue Button) They said all kinds of thigs..." all intake/exhaust restricted, engine midfire on 4 cylinders..." Had to be towed to shop. Results: a valve spring had cracked, ruined push rod, piston, connecting rod, and few more things!! W 47K iles it was totally covered by GM Basic 50K miles/5 years powertrain waranty. Total upper head rebuild w gaskets , a/c charge, more!! Runs better than ever after 1 month now!!

good luck!

jim Hay · #4 07-26-2019, 01:15 PM

After changing the fuel injector for cylinder six with no improvement the shop took off the valve cover and discovered a broken exhaust valve spring for cylinder six. Fortunately, it did not do any other damage. Purely a coincidence that I had just added gas. They did not charge me for the fuel injector. I did use pure gas not the 10% ethanol gas so it was less likely to be water-related anyway.

Thanks to everyone for the feedback.