Po171 and po174 HELP!!! | Ford Explorer Forums

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Po171 and po174 HELP!!!

Sarahjevo17

New Member
Joined
May 18, 2024
Messages
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City, State
Winston, Oregon
Year, Model & Trim Level
2000 Ford Explorer Ltd
I just replaced fuel pump and mass airflow sensor on 2000 Ford explorer limited and I get po171 and po174 too lean codes. I won't drive it because I'm afraid of it getting stuck somewhere. I don't work on cars so how can I solve this issue myself? I have attached pictures of the obd2 error codes

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System too lean on both banks, first I'd check fuel pressure to make sure it's around 60PSI, and then wonder about vac leaks, and would clean the MAF sensor just in case that's it, if it hasn't been cleaned in a while.

You can look around for vac lines that fell off or cracked and leak, and selectively plug off vac lines or vac ports from the intake to see if it changes the long term fuel trim % and/or engine runs better, or if all else fails then it may be the intake manifold gaskets need replaced. Sometimes you can spray starter fluid or release propane around a suspect area and find a leak due to the engine running better while doing so, or you can plug off the intake at the snorkel to the air filter box and inject smoke there, or elsewhere at any vac line (besides the past the valve on the vac line valved for the tank evap line) to do a smoke test to see if you find any leaks that way.

If you don't work on cars then what could remain besides taking it to a shop? You can get a fuel pressure gauge loaner tool free to use (put down a deposit on it) at some of the major auto parts stores like Autozone, Advance Auto, OReilly's.

Your picture shows LONGFT1 is 13% but what is the LONGFT2 %? If they are much different, I would suspect intake manifold gaskets are leaking at a different rate, rather than an upstream vac leak from a hose/etc or dirty MAF sensor which would tend to make both banks nearer the same high fuel trim %. I could be wrong about that, but you have to start somewhere.

Is it dying while you drive it? Was it running poorly or you just saw the dash check engine light as the first symptom? If not running badly, and if it doesn't get worse, then it may still be driveable, at least to a shop or to get a fuel pressure gauge if you need to do that. I am assuming you don't have any other codes, like no misfire codes. I don't want you to get stranded but if it is a hardship not to drive it, I might.

You might also check the two bulk wiring harness connectors under the hood, near the firewall as a bad connection there could cause a weak fuel pump, as could bad wiring to it. More info here: 2nd gen issues? Try this first!

There are also 2nd gen wiring diagrams linked below in my sig if you think it might be wiring, could use a multimeter to check resistance at both ends of the fuel pump wiring and voltage at the pump, though much of what I've stated may seem beyond your skill level if you don't work on vehicles.
 






It’s your intake manifold o rings or “plenum gaskets” all 4.0 engines do this, the o rings dry up and air, dirt and soot get past them

You need new intake gasket o rings

You can find many threads on this it is incredibly common repair

O Rings are like $20 for upper and lower intake sets…. Injector o rings a few bucks more. This job takes a 4-6 hours for a novice mechanic. I can do it in less then 2 hours because I’ve done many many of them

There are a couple of speciality tools you will need, skinny torx bit driver to get to the intake screws

A 2000 sohc engine has a upper intake plenum and a lower intake there are lower rings where the intake meets the heads and there are upper rings where the lower intake and upper intake plenum meet
I would suggest doing both sets
Also a very good time to replace your injector o rings and hats (injector seats) 12ea injector o rings, 6ea insulators, hats or seats whatever you want to call them, it’s a hard plastic cup that the top of the injectors sit inside


Good luck! Let us know if you need help finding how to threads or videos on sohc intake o rings / gaskets
 






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