Hey guys my dad has a 96 F150 XL with a 300 6cyl. has lean codes PO171 (lean bank one) and P0174 (lean bank two). When cold, it cranks just fine and runs just fine but when its be ran for a while it hard as hell to start...it staggers and knocks real hard. Dad has to press the gas pedal to get it to straighten up after a few seconds. We've replaced the intake gasket, MAF sensor and EGR valve. There are no vacuum leaks and smoke test didnt show anything. PLEASE HELP!!!!!

 

First of all did you disconnect the neg. battery cable when replacing/cleaning any of the electrical/sensors/parts? This step is a MUST.

If you did not do the above step, try it, wait 5 minutes, reconnect and take the truck for a drive to reset the computer. Let us know


Did you repalce the O2 sensors?
How did you get codes? Any pending codes?

I wonder if the DPFE is not sending the correct signal to the computer.


Miles on the odometer?

 

Yes we did disconnect the battery before doing ANY work. Still getting lean codes. We recently replaced the EGR valve but not the sensor near it. We plan on replacing the O2 sensor in front of the cat. tomorrow. miles are 165000

 

Do let us know after replacing it. We'll try to figure out a way with what we know and with some research on the problem.

 

You may very well have a Mass Air Flow sensor problem. This could be the air filter, an air leak in the air filter housing, or a dirty mass air flow sensor.

 

done replaced the MAF sensor. cleaned it with carb cleaner and now only got P0171. Changed the o2 sensor and still the same problem. any other ideas?

 

have you checked your fuel pressure? what do you come up with?

 

I dont remember the number but we replaced the fuel pressure regulator, bank 1 o2 sensor, maf sensor, egr valve, and fuel filter. no vacuum leaks anywheres and smoke test showed no breaks.

 

what prompted you to change the pressure regulator? did you have low pressure? did it fix the pressure issue?

 

we got told it had low pressure so thats why we changed. it. still got the same problem tho. i wonder if it could be the spark plugs?

 

did you check the pressure after replacing the regulator? often times on these vehicles a hard start warm is a lack of fuel pressure......the pump could be going bad....

have you pulled a plug or two? it never hurts to know the condition of the plugs....

 

im not sure if it did or not. i wasnt with him when he got it replaced. We are going to change the plugs this weekend.

 

I have the same pickup with the same problem but my truck has dual tanks when i start it hot on the front tank it shakes and skips like hell but if i just flip the tank switch to the rear tank the truck smoothes right out compared fuel pressure between frt and rear tank and frt is 7lbs lower also if i reset the ck engine light and just run on the rear tank the truck runs fine and never sets the codes or light again hope this helps Irv

 

Dads truck does it on both tanks. the thermostat only climbs about a quarter of the way up and his fuel mileage has gone to hell in a hand basket. its agrivating as hell

 

Did you ever figure out the problem? We have had a couple of warm days here this past week in MD and my 96 with 144k is starting to do the same thing! Won't start after being run unless I gas it, but if it's been sittin it'll start fine. I was thinkin fuel pressure regulator but I don't just want to throw parts at it and not solve the problem. I appreciate any help. Yes I know this is an old thread, just curious to see if the problem was ever solved before I start a new thread.

1996cyl

In the couple months I have owned this truck it has caused nothing but problems and an empty pocket. I bought a six for reliability...