Hey guys, got a 97 dodge ram 1500 with the 5.9 magnum 140,000 miles, chasing a p0172 code

Live data shows -33% STFT, plugs also looked pretty rich/black sooty, also have white/grey smoke exiting exhaust when revved in park

Pre cat O2 sensor, MAP, and injectors all appear to be good, i verified this by swapping known good ones from another truck with no changes (also a 97)

PCV valve rattles when shaken, assume its good

ECT on the scan tool matches the gauge

Vacuum gauge showing engine at idle producing around 18-18.5 inch so i assume rings and head gaskets are good

UPDATE

Changed fuel pump/regulator with no change

Any advice helps, i have a scan tool, as well as a multimeter

Thinking perhaps clogged cat or vacuum leak now?

 

Testing fuel pressure would be a good idea, trouble is, the 97 had that plastic fuel rail, with no test port.... so, gotta get creative to put a gauge on it.

 

Or, change the fuel rail set out for the metal style with the test port on it. With all of the hot weather we're experiencing these days, might be a good idea to change it out to prevent the truck from possibly catching fire. Should be an easy item to pickup at a pick & pay salvage yard...

 

Didn't they change genders on the fuel line connection to the rail at some point? I seem to remember something about that, but, cannot verify it.

 

I believe that fuel line connections may have been in slightly different places, however, there should be enough of the metal fuel rails still available in salvage yards on Rams, Dakotas, Durangos, vans, etc. to be able to match one up with the plastic style to make it a bolt-on swap.

 

Hey so little update

Went ahead and changed the fuel pump with a carter, as well as the lines leading to the TB because i did find a slight leak in one, no change, still showing -10-15% fuel trim in STFT

Haven't tested fuel pressure, but since i have swapped the new pump in i'm doubting thats my issue, gonna check for vacuum leaks next i guess

also getting a slight white/grey smoke if i rev the engine in park, i assume unburned fuel, no sweet smell to it

 

How old are your O2 sensors?

 

The upstream is fairly new, maybe a year, but i swapped it with one from my 98 that is a known good with no change, verified that the part #s was the same

The downstream age is unknown, but i didn't think it really had a effect on the STFT?

 

Yeah, downstream shouldn't be a factor.....

But, your PCM is pulling fulling, not adding..... so, I doubt it's a vacuum leak. Wonder if you have a leaky injector.......

 

That was my initial thought as well, the injectors that it HAD in it was some cheapo amazons, they was pretty new, but i pulled them and replaced them with injectors from another truck with no change

I also checked the ohms readings on all of them and got basically the same reading, maybe a .2 difference

I part these trucks/fix frames on the side, so i typically have several i can switch parts on and off from lol