04 4.8 fuel pressure regulator

[Scott Mclay]

Thanks man I appreciate it it's just a work truck but I want to try to keep it running as best I can so I don't put miles on my 17 I really appreciate it

[Scott Mclay]

So I'm going to be doing the intake gaskets this weekend but I've been thinking about this all week I just unplug my mass airflow sensor with the truck running in the idle hardly even changed is that normal or could that be a problem with the maf and the air intake temperature

[riverbanks]

Always have key off for any sensor checks,if you noticed nothing,then it's fine,a improvement,then worth looking into

[Scott Mclay]

I hate to say it but I hope that it is these intake gaskets if not I'm just going to take out the parts Cannon and do is the map sensor and the mass air flow and that only leaves me with an O2 sensor

[Scott Mclay]

Besides the p171 the gas mileage is absolutely horrible

[riverbanks]

Quit beating around the bush,you know it's gotta be done,lol,pull up your knickers and get in there,that's the best I can do for motivation

[Scott Mclay]

You are right with that also explain a stumble at 65 or 70 giving it very very light throttle it shakes a lot

[Scott Mclay]

Got home from work today and took the intake off I don't know what I'm looking for there was a lot of oil inside of the gasket in the intake where it shouldn't be and they were a green color would that be Factory most aftermarket ones I've seen are blue like the Fel Pros I have any other information would be helpful thank you

[CamGTP]

Oil in the intake is normal because the truck has the PCV hose going into the valve cover on the drivers side. The oil mist over time will make it's way into the intake, they all do that.

 

The factory gaskets are orange if I remember right. The new ones are green and if the color didn't change some are still orange depending on who makes the new gasket.

[Scott Mclay]

As far as I can tell these gaskets have never been changed nor has the intake ever been pulled off

[Scott Mclay]

Well i went and did the gaskets and put it all back together and all was good in open loop operation, when in closed loop back to same thing,but when i first started it, it was smooth and good . I gove ,02 sensor live data shows it going up and down to extreme very rapidly, please help

[CamGTP]

O2 sensor movement is suppose to switch up and down rapidly, that they how they work.

 

450mz is stoich and they will switch lean and rich of stoich to correct fueling in real time.

 

You should be more concerned with your fuel trims, if that scanner can watch fuel trims see what they say. Normal operation is probably +/- 5-8% of zero on both banks. You'd know if you have a problem if the fuel trims are super negative at like -20% or if the fuel trims were super positive at +16% or more.

 

Doing the intake gaskets should have stopped the lean code from coming on if you have no other issues with exhaust leaks or a bad o2 sensor.

 

If all that checks out you maybe have to go into it more. Like doing a crank/cam relearn. Doing a compression and leak down test.

Edited December 7, 2019 by CamGTP

[Scott Mclay]

I had a stft at 25% dont remember  which bank still has the 171 code

[CamGTP]

Figure out which bank and note it. Then swap front o2 sensor side to side, if the problem follows you have a failing o2 sensor.

[Scott Mclay]

Thanks . Does the heated o2 have to do with why it runs good when cold