I’ve had a p0171 code for a while now and hasn’t had an effect on my drive ability. I’m cat-less and always assumed it was for that. Last weekend I driving in the dirt and my acceleration started to cut out, would just bog when I pushed the gas pedal. I slapped red line a few times and it seemed to go away. On the way home something tripped and it felt like the truck went into limp mode for about a mile or 2 then went right back to normal. The following week it got worse and worse, horrible gas mileage, longer cranks to start, no power going up hills and then when the weekend hit it died completely. Would crank but no start.
It feels like I’ve read through every thread ever written and I’ve tried everything that solved so many people’s problems but still nothing. Sometimes it starts up and idles beautifully, yesterday I even got to drive it around town. But today it’s back to cranking and not starting. Finally got it to start and stay running while spraying brake cleaner in the intake, even stayed running when I stopped spraying. I let it get up to temp and then went for a test drive, soon as I push the gas pedal when it’s in gear it stumbles and wants to stall. In neutral the rpm’s will go up. Had to get the rpm’s up in neutral and drop the clutch a few times to get it back up the driveway
Things I’ve replaced in the passed few days:
MAF, TPS, spark plugs/wires, both o2 sensors, fuel filter, timing belt, thermostat, water pump, all drive belts and fan clutch
Things that were fairly recently replaced:
injectors
coil packs
fuel pump
all vacuum lines
someone help. What do I test next? I need to get access to a fuel pressure gauge for readings to report. Also, can’t check compression because I have time certs in the head and not certain they will stay in if I pull the spark plugs

 

what year and what engine?

what does p0171 translate to?

 

1999 3.4L
P0171 is system too lean

 

i would repost this in the 1999 sub-forum

 

I had a p0171 on my 2000 suburban. I had to clean the fuel injectors. All but 2 out of the 8 were clogged. Worked just fine after that. But boy did it use more gas then.

 

Are using a K&N air filter, or something similar that needs to be oiled?
It was pretty common to see the MAF get an oil film on it from the oiled air filter(too much oil sprayed on), then anything that got past the air filter would stick to the MAF, desensitizing it. Sometimes cleaning the MAF worked, other times it needed to be replaced.