HELP ME!!!

[afpj]

I understand where you’re coming from, but from what I’m reading in this thread, you started with a knock sensor code , change the knock sensors and you still have a knock sensor code. Since these trucks are kind of peculiar to certain aftermarket parts especially knock sensors and spark plugs, that’s why I recommend considering that in the back of your mind still. Definitely do the easy stuff first because knock sensors are a pain in the butt from my perspective .

Can your scan tool look at knock counts or timing advance? Might see what those values are before during and after the stumbling process. A tech2 would be kind of helpful at this point Good luck, let us know what you find

 

[Fless]

I’m going to get a fuel pressure gauge and check the pressure this week. What PSI am I looking for? At idle it’s 50-60 psi right? Is it the same while driving?

Is your 5.3 a Flex Fuel engine? (Is the 8th character of your VIN "Z"?)

 

[Fless]

Fuel Pressure specs, 1999-2006 Haynes:

 

[theprovider]

Is your 5.3 a Flex Fuel engine? (Is the 8th character of your VIN "Z"?)

It’s not a flex fuel. So I attached a gauge to the fuel rail and it looks like I’m getting weak fuel pressure. At idle it’s ready around 45 psi. Picture won’t post from my phone for some reason. I need to get a longer hose to see what’s happening while I drive. If I give it gas it doesnt move passed 50 psi

https://flic.kr/p/2f7gG8p

 

[theprovider]

Fuel Pressure specs, 1999-2006 Haynes:

View attachment 218119

Hmmm. At idle (key on) it’s reading 48. My vin has a T not a Z though. When I turned the key on and engine not running it’s reading 52 psi....so maybe my fuel pressure is fine. I’ll see what it’s supposed to read at idle. I’ve got a Haynes

 

[theprovider]

My wife held down the peddle at 2k rpms. I expected to see more movement.

 

[swathdiver]

Without the manual for your truck, who knows what it should be? I do know this, a scan tool will show actual fuel pressure and commanded fuel pressure and has short and long term trims that show you if the pump is keeping up with what the computer wants.

Now my engine is a different generation but the fuel pressure is always 43.5 psi running and might drop to 42 at full throttle for a second or so. I just checked it this morning and LTFTs were 1.38; whatever that means. Haven't read the manual yet.

When you shut the engine off, how much fuel pressure bled off within two minutes?

 

[SnowDrifter]

What's the pressure doing when it surges?

 

[theprovider]

What's the pressure doing when it surges?

I haven’t had a chance to check the pressure when it’s surging. Need a longer hose to pull the gauge up through the hood.

My scan tool does show low trim and high trim fuel pressure. The freeze frame I posted shows those levels after the cel went off. According to some people online the trims were in the correct range for the truck.

Also the Haynes manual says 55-60 psi with engine off and mines reading 52. With engine on it drops to 45/48. I unplugged the FPS vacuum like while the truck was on and the gauge spiked to 55 psi.

 

[swathdiver]

I haven’t had a chance to check the pressure when it’s surging. Need a longer hose to pull the gauge up through the hood.

My scan tool does show low trim and high trim fuel pressure. The freeze frame I posted shows those levels after the cel went off. According to some people online the trims were in the correct range for the truck.

Also the Haynes manual says 55-60 psi with engine off and mines reading 52. With engine on it drops to 45/48. I unplugged the FPS vacuum like while the truck was on and the gauge spiked to 55 psi.

Can you stick that gauge under the wiper blade and take a drive?