So I've got an 01 5.9l 201k that's running rich and misfiring. It'll run good for about 3-5 mins on a cold start but then once it warms up starts misfiring slightly. There's no check engine light either and I can't really tell it's misfiring when driving either but when you put your hand up to the exhaust you can tell. It's also getting fuel in the oil, I'm not noticing the level increase much but I've got 500 miles on this change you you can definitely smell it. I removed the cat because all of this destroyed it. Recently replaced both O2 sensors, new plugs, new wires. Im not the most experienced so looking for input. I'm leaning towards an injector being damaged, and sticking open and flooding a cylinder? Would that explain why if it sits overnight it'll run good for the first few mins because the previous gas went past the rings?

Also yesterday I was cleaning the IAC and messed it up, the misfire went away and was running strong but idling at 1400 rpms. Bought a brand new one and threw it in and went right back to what it was doing. Idk if this says anything. Also I didn't do the cap or rotor on the distributor, thinking about doing that within the next few days. Listened to all of the injectors with a screwdriver and they're all ticking, and all sounded similar. Cleaned MAP this morning as well but not sure if it did anything, seemed very difficult to actually clean that thing through the small hole.

Here is live stream data from my OBD2 around the time it starts misfiring
Load_pct - 3.9
Shrtft1%- 3.9
Shrtft3%-32.8
Longft1%-0.0
Longft3%-40.6
Map(kpa)- 34.0
RPM-721
Sparkadv-8
IAT(f) 93.2
Tp%-12.2
O2b1s1-0.760
02b1s2-0.140
Shrtftb1s1-3.9
Shrtftb1s2-99.2

 

What brand O2 sensors did you install, and did you change them because of this particular problem?

 

Yeah that was the first thing I replaced. I got a P0420 and replaced the sensors, then I realized the cat was toast and cut it off and put a piece of pipe in. I used Bosch sensors.

 

Bosch sensors have a history of failing very quickly, Use NTK. You might monitor what the pcm is seeing as far as engine temp. A cold engine needs more fuel, As it warms up it needs less. If the pcm is constantly seeing a cold engine it will feed it more fuel. You can test if a injector is leaking by putting on a fuel pressure gauge and see if it drops after you shut it off.

 

Sounds good I'll go get a fuel pressure tester Tuesday and try it out. This Bosch sensor only has 10 miles on it and made no difference when I put it in

 

I tested the fuel pressure today. 48 running after shut off drops to 40 in under 10 seconds and within 20 mins was at 30 psi

 

That's acceptable.