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Between a favorite shop and I, working on clearing a P0171 code on my 2003 2.3L Ranger, was wondering if anyone had any suggestions. So far...
When the code first appeared:
- Checked fuel pressure. Stable 59PSI at idle and while revving.
- Swapped O2 sensor for Motorcraft.
- Installed new PCV valve, hose, and breather hose.
- Replaced air filter, cleaned MAF.
Code P0171 came back the next day.
- Had a vac leak on cylinder 4 intake manifold. Manifold was fine with no cracks, thank heaven. Replaced intake manifold gasket.
- Replaced valve cover gasket while apart.
Assumed this was the cause of the code, but it returned.
- Replaced MAF.
At this point, after several drives, code stayed away for a day.
Returned, the next morning.
New feature! Also now I have a low, stumbling idle when first started from cold.
Two new pending codes have appeared for P2195 O2 Sensor Signal Biased/Stuck Lean and P0304 Cylinder 4 Misfire Detected.
Any suggestions for a fix on this?
The truck actually runs really well outside of these issues.
It's the best truck in the world and I'd like to keep it running!
Is there freeze frame information? A cold P0171 is different than a warm P0171. Idle versus open throttle also. Might want to add some information about the engine and the situation too. Three days or three months problem? Good luck.
I didn't note the freeze frame information but I can grab it next time I'm back where it's parked. The misfire pending code spooked me off driving it until I can get it to a shop. I remember the freeze frame said the VSS was 0 and the idle was 900, if I recall correctly.
I remember seeing the light on when I started driving up a hill. Dunno if that was when it came on or when I noticed.
I'm not sure what to say about the engine, it's the 2.3L Duratec. Everyone who has driven it has been impressed with how much power it has, so I assume that's good? It usually runs smooth. Put new sparks/wires/coil pack on it last year since that was neglected by the previous owner. Is that the kind of info you mean?
Problem started March 5, 8:30 AM. I pretty much jumped on it the moment I saw the CEL, I love this truck and try to keep it happy.
I meant more about age, condition, and mileage on the engine. Like the comment about the PO's poor maintenenace. Is it an old worn out engine or low miles survivor?
A bad injector seal might cause a specific cylinder misfire and a lean code. The elastic seals tend to leak more when they're cold. If you have live data you can watch fuel trims while spraying small amounts of carb cleaner on seal areas. Spray, watch, and wait. It can take a little bit for the liquid to get through where air just flies through. Watch out though, carb cleaner can dissolve paint and soften rubber.
Oh! I totally spaced that. It's a 2003 with 138,000 miles on it. Manual trans.
New to auto work. I don't know what parts are the fuel injectors when I look under the hood. I can identify a lot more of what's under the hood now than I could a year ago but I don't know where the injectors are. Near the fuel pressure port?
I did change the fuel filter last summer. The problem you describe makes sense, if the injector is plugged or leaky. Anything safer to use than carb cleaner? If we're worried about a leaky seal I'd be concerned about creating a new problem using it. Edit: I see the seals are replaceable on RockAuto, nevermind.
Last edited by King of Mercia; Mar 14, 2025 at 05:54 PM.
Reason: clarity
The key is to keep an eye on the short term trim data right after you squirt a small amount on the area. As it gets sucked in and burned the trims will drop, then go back up. Sometimes it has to travel a short way before it actually gets to the air leak spot.
You might get the same effect with water though. As the water seals the leak the trims will drop then go back up when the air starts leaking again. Never tried that. Actually, I've only done the carb cleaner trick once, but it worked so well that I keep repeating it to people. It was obvious.
Your fuel trims are very high. But it's hard to tell if it's an intake leak problem or an O2 sensor problem since you have both codes. If it was mine I'd pull a few spark plugs to see if they shows signs of excess fuel as the PCM tries to correct for a bad O2 sensor reading or if they look clean and lean due to a big air intake leak.
If the plugs are a dark and close to fouling the O2 sensor seems more likely. If the plugs look normal then a leak seems likely. As you can see your video, there's a very long stretch of intake hose after the MAF sensor that could have a crack or hole in it. Worth close examination.
I also notice that your engine temperature is pretty high. 226 F. Lean mixtures tend to burn hotter, but the cooling system shoudl be able to handle that at idle. Might be a clue. And your MAF sensor reading seems in range, but on the low side. Another possible clue that there's an intake leak.
Sometimes you just have to assess a bunch of clues at the same time. Good luck.
Any chance you could install a newer intake manifold with out the IMRC, and get tunes to get rid of those codes?
I'm having a similar problem like you same year truck but with the 3.0, no one makes or can't find an intake manifold, I patched mine up with TA-31 sealant it worked but I would really like to find a new one.
That's currently my plan. I've searched all over the web and I've found many people talking about swapping to a flapless intake, without swirl valves. Three or four separate threads about doing it.
But zero of the users followed up on if it worked.
It looks like that's likely what I'll have to try doing. I don't know anything about tuning, who to ask, what to look for. If anyone knows about tuning lemme know.
Edit: I believe it's EEC-V and there is no CANBUS in a 2003. I've seen posts online about tuning to get rid of IMRC, but it's either for high performance cars or Focuses. Dunno about a Ranger.
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P0171 Lean Code Keeps Reoccurring
