Cel Flashing At Me

fataugie · September 29, 2007

I have a quick question....I have a 2003 2500HD 4x4 GMC with a 6.0L automatic. I filled up today and added a large size Chevron Techtron gas treatment bottle right before a long trip. About 50 miles into the trip, I started getting the engine light flash at me for a few seconds, then it would go away, then it would flash again 10 miles further, etc. It eventually mellowed out some and I see that flashing means it's misfiring so I would take it out of cruise and slow down, speed up, etc until it went away. All the time, the truck was running smooth, the gauges were all in the proper ranges and I couldn't tell there was something wrong except for the light.

Could it be pinging (maybe crappy gas)? Could it be the treatment? I see from searches it could be 10 other things so it could just be a coincidence, but I doubt it.

I haven't treated the gas in probably a year and 15K, but this is the first time I ever had a problem like this. I haven't been to Autozone yet, so I don't have any codes to offer yet. Any ideas before I make an appointment to get it checked?

UPDATE: I just had the codes read....0300 random/multiple cylinder misfire. While I was out, I went ahead and topped off the tank with fuel from a different (trusted) source. It never flashed during my 30+ mile round trip, but the only time it flashed the last time was at expressway speeds of 70+ and I didn't reach those on this trip so who knows.

fataugie · October 1, 2007

Anyone?

*TAP* *TAP* *TAP*

Hello....is this thing on?

KPSNOOKA · October 7, 2007

Anyone?

*TAP* *TAP* *TAP*

Hello....is this thing on?

I WAS HAVING THE SAME PROBLEM (KINDA). IT SEEMS THAT ALMOST EVERY TIME I WOULD GO ON THE HIGHWAY MY SES LIGHT WOULD COME ON WITHIN 100 MILES OR SO. THE TRUCK WAS RUNNING FINE SO I IGNORED THE LIGHT. IT WOULD GO OF ON ITS OWN IN A FEW HUNDRED MILES. I ALWAYS PUT PREMIUM IN IT ON THE HIGHWAY. THE LAST TRIP I TOOK I PUT 89 OCTANE IN IT AND IT TOOK ABOUT 1,000 MILES BEFORE THE LIGHT CAME ON. I KEPT GETTING P-0300 RANDOM MULTIPLE MISS FIRE. I AM STILL TRYING TO FIGURE IT OUT. NOW I HAVE RANDOM STALLING. MY TRUCK SITS OUT 24/7. I GO TO WORK AT 6:30 AM IT RUNS FINE. COME HOME AT 3:PM TRUCK STALLS AND RESTART IT SOMETIMES FINE AND SOMETIMES STALLS SEVERAL MORE TIMES. GO OUT IN THE EVENING IT SOMETIMES STALLS BUT 9-11 PM ON THE WAY HOME RUNS FINE. I AM LOST. THIS WEEKEND I TRIED A NEW COIL AND A NEW FUEL PREASURE REGULATOR. I HOPE THAT THEY WORK. IT HAS TO BE SOMETHING WITH HEAT. I WILL LET YOU KNOW THE OUT COME WHEN I FIGURE IT OUT.

fataugie · November 18, 2007

Update: I purchased Autoenginuity's software package including the GM enhancements to view every possible sensor in this truck. There is a history for misfires on Cyl 1, 6 and 8 and they are insanely high. 58K for Cyl1 if I remember correctly and the others are close behind.

I wonder if I knocked some crap loose from the tank when I put the gas treatment in and it's screwing with the fuel injection. I don't see any obvious signs of damage to any electrical wiring for those cylinders, but I know that doesn't mean squat. The engine only has 58k on it so I'd be hard pressed to see how plug wires could go this fast.

Any thoughts?

C & A s Dad · November 18, 2007

Tony, you will think I am crazy but typically if this happens after refueling, a loose gas cap is the culprit. Has your light come back on since your refueled again? If not and your truck is running good, you lilkely left the cap loose. This happens all the time.

fataugie · November 18, 2007

No, it's not that. This is a misfire happening when driving at speed.

The CEL flashes which indicates a misfire.

The code is P0300 which is random cylinder misfire.

Tony, you will think I am crazy but typically if this happens after refueling, a loose gas cap is the culprit. Has your light come back on since your refueled again? If not and your truck is running good, you lilkely left the cap loose. This happens all the time.