The lead up:

2003 Ram 2500 4x4 5.7 HEMI. Driving home it seemed to be missing all of a sudden especially under any load/accel. As soon as I slowed down to 5MPH it wanted to die, parked and it died.

It was throwing a bad O2 sensor code (high voltage) so I went ahead and replaced it, cleared codes and that code did not come back. Truck would not idle, added some HEET and injector cleaner and at least it will idle now (unhappily).

CEL codes are P0003 and P0172. Truck will start with a little throttle application, idles terribly like 4 cylinders are missing. Will not rev over 3900/4000. * Of note, it did that 4000 RPM limit thing a year ago and after some injector cleaner and a long drive it went away.

I replaced the in tank fuel pump (Airtex): No improvement
I changed the spark plugs: No improvement
* All were old but all looked the same (my knuckles hurt now lol)
I swapped the throttle body (with IAC) with a new one: No improvement
I swapped the ambient air temp sensor: No improvement
I cleaned the throttle body: No improvement
I checked for vacuum leaks using the unlit propane torch: No leaks found
I wiggled all of the injector cables: No improvement while running

So now I am looking for ideas on what to test next and what those codes indicate. My only remaining ideas are a clogged cat (but why would it have gone away a year ago?) and testing every single injector. Many thanks in advance.

 

P0003 Fuel Volume Regulator Ctrl Circ Low

P0172 1/1 Fuel Sys Rich

What to test, no clue there but those are what the codes indicate. Sounds like you are running super rich though

 

welcome to the site

Ive gotta say it......pull the valve covers and check each and every valve spring and make sure none are broken

 

You said adding heet helped get it sort of running. Heet is just anhydrous methanol or isopropal alchohol, If that did in fact help, my guess would be a fuel system fuel of water. These don't have a recirculation fuel system, the fuel reg is in the tank along with the pump, See if there is someplace in the engine compart,ent you can pull a fuel line and run some gas into an open ---clean--- container, see if you get some water out of the tank.

Its also possible it could be valve springs, as the 03 were known for such issues

 

Thanks for the replies. Valve springs look good. When I took the old fuel pump assembly out I noticed the gas looked a little darker than i would have expected. Maybe lots of build up? No way to get fuel from the bottom easily that I can see. Maybe fill it up with premium and hope it evens out the ratio?

Anything else to check, poor truck it takes a lot and never rolls over like this

 

Also, no one seems to think its the cats, that was just a hunch off of reading other posts. Now that it barely idles I would imagine it wasn't the cats.

 

If you are running rich, maybe a valve is stuck open, or an injector is bad. It really sounds like your truck is in limp mode right now though. Do you have a way to clear the codes? May clear them, throw some premium in the tank with either some injector cleaner or octane booster and see if it improves or if the codes pop up again. Might actually call a dealer and just say these are the codes I am getting, what do you look for when diagnosing them. and see what they say.

 

Yes, i clear the codes and they come back after revving it a few times. I will call the dealer and see if they are any help. I appreciate all the feedback.

Whats weird is that it wont rev past 4K or so. Logically that sounds like timing issues or running lean but nothing points towards those causes.

 

Just found out the 4K rev limit is the rev limiter when in park. Haha jokes on me, but it still wont idle well.

 

Today I replaced the PVC valve with no improvement. I also figured out I have no EGR, apparently it was not added until the 2004 model year.

I am just about out of ideas other than to fill it up with premium and a few bottles of HEET. Any ideas left?