ueww40

I have a 1997 F150 with 4.6 ltr engine. I am getting one code and this one code only P0171. In my estimation this will eliminate most air leaks behind the MAF, a leaky gasket between the intake manifold and the TB, a leaky gasket between the TB and the EGR, bad fuel filter or pump and other components like the DPFE etc. because all of this would affect both banks. Correct me if I am wrong please. But my problem is reserved for bank #1 (passenger side). While the engine is running I sprayed starter fluid around bank #1 intakes and there was no change in engine rpm. So if there is still a leak somewhere, where would it be? What is my next move to check? All vacuum hoses connected to the TB have been replaced already. Question there is a vacuum hose that goes from behind the TB toward the firewall. I am not sure about that one. Where does this line go to? If all of this is ok, what else could there be?

Tom56

Check the PCV valve. Little valve coming out of the pass side valve cover. They go bad often.

Frank_Ford

Also try cleaning your MAF sensor. This, like the PCV valve, is very low cost and improves the running of your truck. While you are at it I would change the air filter.

the vacuum line that goes to the firewall is most likely the line that controls the blend door on your heating and A/C system.

Frank_Ford

Also try cleaning your MAF sensor. This, like the PCV valve, is very low cost and improves the running of your truck. While you are at it I would change the air filter.

the vacuum line that goes to the firewall is most likely the line that controls the blend door on your heating and A/C system.

ueww40

Ok, I checked the PCV valve by pulling it out of the valve cover, started the engine and put my finger under the valve. I felt lots of vacuum and i could hear the valve snap up and down easily. I guess that means the PCV valve is working fine and there seems to be no leak. Where do I go from here? I will clean the MAF sensor asap. Need to get the proper cleaner, but I don't think that the MAF sensor is the problem and the air filter is only several months old. Any other suggestions? Help! Remember the code is 0171 only, passenger side bank. The 02 sensors could be the problem but its a long shot or am I wrong.

ueww40

Actually the line that goes towards the firewall was actually the vacuum line that goes to the PCV valve on the passenger side as I found out while checking the valve

the vacuum line that goes to the firewall is most likely the line that controls the blend door on your heating and A/C system.[/QUOTE]

ueww40

Please Help! Are there any Ford technicians out there that can narrow it down a little. My situation is that I get this one code only. I inspected my exhaust as well and it looks ok. There does not seem to be a leak in the exhaust. So whatever is happeneing it is happening on bank1 only and that should exclude a lot of conditions that are present if both codes are displayed.

biglee88

We'll there r no bank specific vacume leaks so all it really can be is the injectors or the intake leak really

ueww40

If the injectors were the problem wouldn't the system produce a different code indicating that one or more injectors are failing or do injectors not have their own error codes, just thinking. I will check for intake leaks again. Thanks

ueww40

Cleaned the MAF sensor today. Btw at first I could not find it. The sensor is not where you would expect it to be namely in the TB. It is right behind the air filter in the big plastic housing. Replaced the fuel filter and added injector cleaner to the gas tank. I do not suspect injector problems because the engine actually runs rather smooth. I checked for leaky intake again by spraying starter fluid around the intakes where they mount to the block. No noticable change in engine behavior. I did reset the OBD and now I will have to wait to see if any codes come back.