Definitely do appreciate it swartlkk. Hope the surgery goes well. God bless.

 

I pulled my backup of this thread and although some things were added/changed, I have the thread. The forum is giving me fits about getting the thread updated though. ARGHHH. At least I have it now. The thread title will be changed to remove the IAC and EGR valve cleaning as I do not have that information. It was an edit done after the fact.

 

Last weekend I replaced my fuel pressure regulator, I just scoped out and dug in . The truck starts right up and idles like a top now, not to mention gas mileage has improved significantly. This was definitely the fix it needed. Despite my previous thoughts this fpr was actually really easy to replace. Just make sure you remember where all of your electrical connectors and vacuum hoses go. I had access to air tools so that also made things easier. Truck runs great now.

 

I replaced the fuel pressure regulator on my truck not too long ago. The picture looked exactly like mine when I pulled the plenum off. Pretty easy replacement thanks to this great DIY article, the only problem was the little rod in the center of the tamper proof torsion screw that holds on the FPR was bent. How does that even happen??!!

Anyway, fuel mileage went from 12.7 MPG to 16.1. I believe that is right around where it should be.

 

post deleted.

 

rowe, please create a new thread in the 2nd Gen Tech or Engine/Transmission section. The DIY Article Submission/Discussion is for submission or discussion of DIY articles concerning their content, not tech help with your vehicle.

 

I realize this thread is old and pretty well beat to death, but nowhere in this discussion has anyone touched on what causes the black carbon buildup inside the plenum.

If you've ever taken apart a 1972 or older engine, you noticed how clean the inside of the intake manifold was, and how clean the back side of the intake valves were. With 1973 and later engines, at cruising speeds, a passage is opened between the exhaust and the intake to reduce tail pipe emissions. The passage is controlled by the EGR valve, (exhaust gas recirculation). When the valve opens, the exhaust cools as it enters the intake manifold and sticks to the surfaces in the manifold and everything in its path up to and including the back side of the intake valves. Over time the carbon builds up on the surfaces, and can create other problems and may need to be taken apart and cleaned out. On the 4.3L CMFI and CSFI the entire plenum is subjected to exhaust gasses when the EGR valve opens. When there's a fuel leak inside the plenum, the fuel will disolve the carbon and eventually "wash" the surface. The washed off carbon chunks have two places they can go: One, they can find their way to an intake runner, get past the intake valve and be burned, no big deal. Two, the more likely scenario, is they will clog the drain holes in the lower intake manifold which will allow the plenum to accumulate raw fuel. The drain holes are located in the #3 and #4 intake runners and lead to the back side of the intake valves bypassing the injector nozzles. If you have a leak in the plenum, either #3 or #4 spark plug may show signs of a rich condition. If #4 is running rich, look for a leaking fuel pressure regulator. On a CMFI engine, if #3 is running rich, look for a leak in the fuel pressure or return lines, (nut kit). The CSFI engine does not use the "nut kit". Next time you have the upper intake off, clean that stuff out, and don't forget to clean the drain holes.

 

GREAT write-up. I had mine off and changed in 45 minutes with this article. The only difference I found between my situation and the article was in the symptoms. My plugs on the passenger side had the black soot on them. Not the drivers side. Here is a picture of mine:

 

GREAT picture, a perfect example of "washing" on the passenger side. The driver side looks normal. Most likely the fuel pressure regulator is leaking, but a leaking fuel line to a poppet nozzle is also a possibility.

 

Mine was the FPR, I turned the ignition to on so the fuel would pressurize and watched the waterworks. It leaked out of the adjuster screw on the FPR quite a bit. You can see where the dripping has cleaned the fuel line below it.