4.8is intermittant loss of power while accelerating
 

The 4.8is started doing this yesterday while applying light throttle at stop lights to reach about 45 mph. It's not consistent and does it at odd times. It did it twice yesterday and today it did it while cruising at about 65 on the highway. It's not constant. No CEL. Some folks have mentioned fuel filter, fuel relay and fuel pump. Someone even mentioned the IVM. What are your thoughts?

Always test a few things before you go throwing parts at it.

Fuel pressure testing is QUICK and simple. Test is for VOL and Pressure
Take a peek at the coil tops. Burnt?
Pull all the codes not just the P codes!

I'm going to pick up a pressure tester today. What should the pressure be at the rail?

50/55 psi

I use this one
https://www.amazon.com/OTC-5630-Fuel...ef_=ast_sto_dp
REV X E85 Super Tester Reusable Ethanol Testing Kit - 5 oz
I also use this as way too many drivability issues are trash fuel. Cheap $12!
Background: Had a dealer once play stump "Mr Wizard" by giving me a multiple comeback car with 1/2" pile of service receipts all around poor performance. Scope showed poor cyl to cyl balance under load with multiple cylinders randomly involved. Fuel delivery (Injectors/pump)? Ignition (coils/Plugs)?, Fuel contamination? Pulled a sample of the fuel to show that the car had 33% water/alcohol mix in the tank. Somebody put it in there either at the pump or his neighbor hates him! :dunno:
Drained the tank, added a can/bottle of injector cleaner, added 1/2 tank of quality fuel. Presto change O, problem gone.

I now live by the "test the fuel FIRST" approach for hard to find drivability issues.

Many thanks! I'll let you know what I find. :)

Bentley Manual says
Idle 36.3-46.4 PSI (system pressure)
Engine off 50.76 =/- 2.9 PSI (Residual pressure)

I'm gonna run the test after dinner. :thumbup:

The tester I bought sucked. It essentially leaked gas out at the gauge. Everything was tight. It's going back to the store tomorrow. I ordered the one you recommended and it'll be here tomorrow.

Yep the cheap ones want to see 5-10 psi from a mechanical pump, not 55PSI from a electric pump. Wait until you see the newer cars with 2200 psi direct injected units.

Or an oil-burner with 26,000psi!! :yikes: :D