Po171 And Po174

My sons got a 99 ranger i know f series but you all always help me with my f150. Its giving these codes which led me to mass airflow sens. I sprayed tuner cleaner leaves no residue in mass airflow unpluging battery of course. No service engine light 4 a couple days. Now its back and the problem he has is cranks a long time to start only after all night or all day at school. Other than that it fires right up.Heres what ive done recently.New air filter,fuel filter, dpfe sens,plugs,wires. Was wanting some input before buying a 125 dollar mass air flow sensor. Ill wait til i hear from my friends. Thanks DAVE

Ok i put new mass air sensor on. Great for a couple days then all the sudden died wouldnt start. Set an hour started again but did crank about 8 times. Dont know what to try now. Guess take to shop unless i get an idea...DAVE

Hey Dave
According to my code book P0171 and P0174 is "system too lean, left bank and right bank". Have you checked the fuel pressure? Also , just for grins check for good spark when it throws one of its fits. Check the vac line going to the fuel pressure regulator also. If its still throwing the same codes, and its lean, it could be a pump going out or a bad regulator bypassing too much fuel.

now running decent but when you slow down it downshifts real hard.I took everything off that i could and cleaned and inspected.I know somethings not right by the hard downshift

I agree with unclebubbles! Get a fuel pressure tester!

The too lean condition sounds good to me - hard starting in morning without fuel enrichment

This may not be correct, but I have both a 2001 Windstar and an 2002 F150 and the Windstar is notrious for these codes. See the Windstar forum right at the top of the page.

With the Windstar the problem is the isolator bolt grommets at the bottom of the EGR. Ford used the wrong type of rubber so that the rubber hardens over time and you end up with a vacuum leak between the block and the EGR bottom clamshell. I suggest it may be similar because looking at my F150, the EGR looks almost identical. Its an easy and relatively inexpensive fix if it is related to the problem I am talking about.

In any case, if you have a vacuum leak, you will get the lean codes and you will pull excess oil into the EGR causing hestitation, poor mileage etc, depending on how severe the leak is. My two bits from my Windstar experience.

Some things to check -

If you have a K&N filter, 9/10 times the MAF is dirty and needs to be cleaned. The oil from the filter makes these VERY dirty over time.

Check O2 sensors, but unlikely.

The next most likely issue is the intake mainfold gasket. Ford has a TSB on defective gaskets. If your under warranty, your in luck. Its a do-able job, time consuming but I took it to a shop - $660 to fix. Engines between 2000-2005 are now starting to show this defect. My shop saif he has seen 20 this month since the defect rears its ugly head when its cold.

I only run my o2 for 30K.. 60k's probably average, 100k, they're definitely compromised. As the o2's read, so goes the engine. My 87' 302 gets 17/23 mpg., I think a fresh o2 has a lot to do w/ it. There is accuracy & switching speed that goes south. Lacking other implicit codes, something to consider, but definitely check fuel pressure & bleed down time.