Check engine light, code P0101

What if they have not fully failed yet but are starting to? I am just thinking like similar with the MAF sensor before I replaced it, it was failing but had not fully failed yet as it was still giving a signal just a weak/incorrect signal.

Oh alright makes sense. Well I will try to find a vacuum gauge to borrow I think advance loans a tools so I will look into that. And in the meantime I am going to check the timing chain as it is probably about time to check that anyways.

Alright well first thing tomorrow I will go down to Advance Auto to get a vacuum gauge and test the vacuum pressure. I will be back with the results from that.

Hey. Also, I was looking around in my engine bay after I went to the store, just taking a second good look to see if anything looked strange, etc, and I noticed that on both exhaust manifolds there is a bolt missing. Same spot on both sides, it is on the end closest to the front of the vehicle and it looks like there may be a small gap. Do you think this could be the cause of anything? Would it be a good idea to test if and/or how much air is getting through there with the fog machine? Also I noticed there is no distributor cap/rotor, instead ignition coils. Could the ignition coils be a suspect?

I am back. Unfortunately I have not had time for much the last few weeks, almost all of the water pipes in my house froze and burst along with the septic drain line that froze as well and it was all just a big mess. But back to the truck. I did end up getting a vacuum/fuel pressure gauge the other day so I checked vacuum and vacuum was right in the middle of the specified range for my truck. Then I checked fuel pressure, it was a bit lower then it should be at idle and absolutely no pressure when not running. So, I know the fuel pump is good that was just replaced not even four months ago. Last week I believe it was, I replaced the fuel filter. And today I replaced the fuel pressure regulator. And it is still idling rough.

Well the last time I checked the fuel pressure was before I replaced the regulator and it was at about 47 psi while running and 0 psi when off. I just checked it again today with the new regulator and now it is still 47 while running. But, now this part seems weird to me this I do not quite understand, as soon as I shut the truck off it stuck at 47 for a second then slowly rose to a perfect 55 and stayed there.

Oh okay. No I have not thought to but it does sound like a good idea especially seeing how the MAF was kind of my original underlying cause. I will definitely get on checking that, I will have the results shortly.

I rechecked the MAF power and Signal wires and power is good, 14.34 volts and signal looks good also at 4.65 volts.

Sorry it has been so long been very busy with work it is our busy season. But I tested the MAF signal at different rpm's and yes it increases and decreases with rpm.

Yes I did. I also checked around the sides, front and back of the intake manifold along with the vacuum lines to the brake booster and fuel pressure regulator, PCV hoses and around the valve covers. I also made sure the o-rings on the MAP sensor and EVAP purge valve are in good condition and sealed up tight. And yes I checked the pins where the connector plugs in and the connector itself along with the wires and I tested them all for proper voltage and resistance tested the grounds and all is good.