Another P0300

[intergalactron]

I have a 2020 Tahoe LT, 5.3 Flexfuel, 110,000 miles. It has a stored P0300 code. This code was set during a hard acceleration event (merging on an on ramp). Engine backfired, lost power, engine light came on and was flashing. I let off the gas and everything returned to normal. Engine light turned off within a few seconds. This has happened 3 or 4 times. All similar circumstances, but only the one time I noticed the engine light coming on/flashing.

Other possibly related symptoms: Occasional rough idle. Occasional poor shift quality. Occasional 'surging' (throttle held steady, engine rpm varying).

I'm at the beginning of trying to get this ironed out. Where do you suppose I ought to start looking?

 

[Geotrash]

I have a 2020 Tahoe LT, 5.3 Flexfuel, 110,000 miles. It has a stored P0300 code. This code was set during a hard acceleration event (merging on an on ramp). Engine backfired, lost power, engine light came on and was flashing. I let off the gas and everything returned to normal. Engine light turned off within a few seconds. This has happened 3 or 4 times. All similar circumstances, but only the one time I noticed the engine light coming on/flashing.

Other possibly related symptoms: Occasional rough idle. Occasional poor shift quality. Occasional 'surging' (throttle held steady, engine rpm varying).

I'm at the beginning of trying to get this ironed out. Where do you suppose I ought to start looking?

Fuel pressures.

 

[intergalactron]

Fuel pressure: 40-50 psi
Fuel rails: 450-600 psi

 

[intergalactron]

I did check my MAF sensor, didn’t see any dust or buildup on it. I hit it with a little canned air just to be sure it was clean, put it back, still runs the same.

 

[OR VietVet]

There is MAF cleaner to buy at the parts store. Better than air attempt.

 

[NardDog]

I did check my MAF sensor, didn’t see any dust or buildup on it. I hit it with a little canned air just to be sure it was clean, put it back, still runs the same.

Try unplugging it and see it runs better

 

[intergalactron]

Try unplugging it and see it runs better

That's a good idea. I had a Buick that had the MAF completely fail. Wouldn't run. Unplugged it and it went into a 'safe' engine map and ran fine.

 

[Fless]

At warm idle, what does your scanner say the MAF reading is in g/s? It should be very close to the engine displacement in liters (or "litres" if you go that way...)

 

[intergalactron]

So its cold and snowy where I live so I've kinda back-burnered this. But I was thinking... My driver's side motor mount is shot. Could a little bit of clunking of that motor mount trip the knock sensor, causing some of this surging?

 

[OR VietVet]

So its cold and snowy where I live so I've kinda back-burnered this. But I was thinking... My driver's side motor mount is shot. Could a little bit of clunking of that motor mount trip the knock sensor, causing some of this surging?

Yes. Knock sensors react to noise.