Fuel pressure & misfire question

[Tdean91491]

Alright I’ve looked every where and can’t find a direct answer. I’ve got #3 & #5 misfiring at idle after I drive for 15 or so minutes. I’ve got the DashCmd app with the live data and all. It’s not throwing a misfire code though. New cap, button, plugs and wires. Fuel pressure is 60-65 on start up when it starts to miss it’s around 49. Could I be experiencing fuel delivery problems?

 

[stutaeng]

Yes, but could also be other things. What are your fuel trims when it does this?

An injector intermittently failing open will also cause a misfire, which would also cause the drop in fuel pressure you see.

Need to dig deeper. I wouldn't suspect fuel pump if it primes to 60-65 psi. A fuel delivery problem would usually show up as lean on BOTH banks, by an exact amount. But maybe a wiring issue can cause fuel delivery problems... again you'd see fuel trims go lean.

I would do an injector balance test to see how your injectors are doing.

 

[Tdean91491]

I’ll read the fuel trims on my way from work. I’ll let you know what it reads.