​​I have a Ford F150 1997 4.6L V8. When I turn it on, it will stall if I don't press the accelerator. After pressing it, it stays idling normally at 600 RPM. Heard some popping at first. Replaced all spark plugs and had the CEL on and it was flashing while test driving. As of today, no CEL, no popping. Scanner shows STFT is at 50% w/ LTFT at ~8% in the first 5 minutes. Then STFT drops 15% w/ LTFT at 35%.
I got codes: P0307, P0171, P0174

​​​​​​No exhaust leakage and I found this cut on the left side with some air leaking?


Could this be the problem and what got cut?

 

That could very well be part of your issue. PO174 and PO171 are related to a vacuum leak, and you have a vacuum leak. PO307 is a cylinder misfire on cylinder 7. Try reseating the plug wire on cylinder 7 on both the plug and the coil pack.

 

Yep part of your issue but not enough to get you anywhere near 50 or 35% fuel trims. Check PCV hosen, make sure PCV is in the valve cover, verify your air filter hasn't come apart and that the airbox is closed up right.

 

PCV hose and cover are good no leaks. I checked the air filter and I saw that a piece of the top part is broken!! Could this be the MAIN cause of the misfire on #7 and the lean codes & the high fuel trims? I will replace the cut line and check other reasons for the misfire tomorrow.

 

No, that's not going to cause a misfire, nor will it cause a lean code. Again, you have a VACUUM leak causing the lean codes. That crack may or may not be allowing air to get around the filter, but it is before the MAF, so there isn't any unmetered air getting in.

 

You don't have enough info to determine that this is a vacuum leak. The standard is to verify that fuel trims go from lean at idle and high intake manifold vacuum to normal under load where there is no vacuum in the intake manifold. You can also have an unmetered air leak that is not a vacuum leak causing lean codes.

A mis-assembled airbox or a damaged air filter can cause turbulent airflow through the maf sensor and skew maf readings, causing the engine to run rich and/or lean.

OP: That missing piece isn't a problem. As long at the band clamp can squish the air filter seal between the 2 halves of the airbox, you're good. These airboxes regularly get distorted, bent, broken, etc... so I like to remove the whole thing and carefully assemble it outside the engine bay to make sure the air filter is sealed up.
One thing you might try is unplug the maf, start up the truck and see if fuel trims go back to normal. If they do, I'd start looking at the maf sensor. Also, if you can log BARO frequency, you can quickly diagnose the maf. Expect to see BARO at ~157Hz +- 9 hz. If fuel trims don't go back to normal with the maf unplugged, you've probably got a vacuum leak.

 

He's got at least one vacuum leak in the first pic. And then thanks for reaffirming what I said about the air box not being an issue.

 

Stalling and 600 rpm is a classic IAC fail. Warm idle should be 725 rpm when all is good.

Popping noise, my guess is the PCV valve, - I 've heard the wrong PCV valve make a popping noise every so often with these engines. Due to being too restrictive.

Flashing CEL = misfire. Don't worry about the lean codes until you fix #7 (PO307). Misfire first. Check spark on #7.

That's just broke, they break square like that sometimes. Easy fix. The other piece is still stuck in the elbow. Pull that piece out and install the piece in your hand. When you remove that piece from the elbow, notice the little ring around the tube. That ring is how far to insert the tube into the elbow. That's so you don't push in too far and pinch off flow. You can just measure how far to go for the repair in this case.

Btw, that looks like the AC reservoir line. If so, that's the top canister directly behind the battery.