I have an 09 Denali XL with the 6.2. Lately I’ve experienced a once-in-a-while stumble in the first few minutes of running. It usually happens with a cold engine, in the first mile of driving, upon tipping in the throttle after coasting for a distance (the road from my house is downhill). It feels like the engine wants to backfire or stall but after the stumble it runs fine.
Yesterday I datalogged all my trips. There are no misfires recorded, no pending or active trouble codes and no CEL. The stumble never happens when I leave the office and head home (level roads) as far as I recall.
I noticed on the logs that there are occasional big drops in indicated fuel pressure. Generally, pressure is around 43 psi, give or take. But I noticed readings of 16, 19, 25, 17, 13, 12, etc.
I’m skeptical these are accurate readings because they sudden and are generally bracketed by plausible data. If the fuel pump was failing, for example, there should be enough residual pressure to keep the fuel flowing without a momentary large drop in pressure. Should I look elsewhere for the problem or could I have an issue with fuel pressure?
Yesterday I datalogged all my trips. There are no misfires recorded, no pending or active trouble codes and no CEL. The stumble never happens when I leave the office and head home (level roads) as far as I recall.
I noticed on the logs that there are occasional big drops in indicated fuel pressure. Generally, pressure is around 43 psi, give or take. But I noticed readings of 16, 19, 25, 17, 13, 12, etc.
I’m skeptical these are accurate readings because they sudden and are generally bracketed by plausible data. If the fuel pump was failing, for example, there should be enough residual pressure to keep the fuel flowing without a momentary large drop in pressure. Should I look elsewhere for the problem or could I have an issue with fuel pressure?
