Check engine light flashing.

CapitalTruck · September 14, 2016

I always thought a flashing check engine light usually indicated that one of the coil packs had gone belly up

Sarviss3 · September 14, 2016

Update. Like u said before I never really drove the truck that much in four years about 15000 miles. So today I drove it 75 miles and 50 of them were on the highway. I averaged 70 to 80 mph with the light blinking, but this time the light wouldn't go off even when I stopped. The truck seems to run fine and it idles at 600 rpms when stopped. So I shut it off when I got home and restarted it and the light went off, took it for another ride and it went back to the normal coming on at 45 and going back off.

txab · September 15, 2016

I always thought a flashing check engine light usually indicated that one of the coil packs had gone belly up

Incorrect

txab · September 15, 2016

Going back to post #4.

No other codes ever than PO300?

Have you checked fuel pressure reading? Key on engine off reading.

How did you "check" the intake gaskets? They are pretty common to leak

have you done a compression check of all cylinders?

Checked injectors and spray pattern?

A crank re-learn may be in order

Sarviss3 · September 15, 2016

No other codes then the p0300. I sprayed starter fluid around the intake and it made no difference. I disconnected the egr valve and took it for a ride and no difference. I was wondering if I should of seen a difference. Didn't get a chance to try anything else, maybe this weekend.

txab · September 16, 2016

Spraying doesn't always highlight the issue

ChevroletTough · September 22, 2016

I had my CEL blinking for a random missfire. Changed plugs and wires (was time), checked injector pulses, fuel pressure, intake for leaks, accel pedal calibration. Ended up being the crank shaft position sensor. Replaced it and had the relearn done.. It runs SO MUCH BETTER! Chased that for a damn year.

Would only do it over 2400 rpms, or when you got real heavy on it. I could get the CEL to blink in park, neutral or driving if I got it over those rpms steady for awhile. I never felt hesitation at all, ever. I also had a high end (non gm) scan tool hooked up and took it for a drive, banks 1,3,5,6 and 7 were all missfiring at random times even when the CEL wasn't flashing.

A GM dealership can tell you if the crankshaft position sensor is out of whack. I got the sensor for like $46 on amazon. The relearn and replacement was $60. I was going to replace it myself, but they had it up on the lift already. You DO need a relearn after it. Despite what some say. The dealership even tried a relearn on my factory sensor, but it wouldn't work right, so they replaced, relearned and life is good. You can try without it though..

Hope that helps.

Best of luck.