MAF bad or lost calibration in ECU?

[I_LIKE_TURTLEZ]

I replaced the MAF and it has a wider value range on the OBD log. I reset the ECU. Next, I tried to train the idle.

I cranked up the car and let it idle til it warmed up a bit, turned on the AC full blast and it struggled a bit. I let it warm another minute or so then turned AC on full blast again. The car seemed to learn the idle. I drove the car to work with no major issues. The RPMs did float a little with clutch in but would settle after stopping for a few seconds. I left early at lunch and afterwards, I tried to start the car and it wouldn't idle... Lol. I'm enjoying debugging and will need to do a writeup once I'm finished figuring this one out.

I had to hold the throttle after start for a second or two them it figured itself out. I'm not sure if I mentioned replacing the EGR purge regulator but I just noticed the hoses to the canister are in terrible shape. It may be the source of a vacuum leak. I'm also seeing P1443, which is related to this canister not functioning correctly.

Cleaning out the original IAC well & reusing it is probably the better option, the problem with new sensors that aren't OEM is they're not calibrated precisely enough so their voltage/resistance readings are often off just enough to make a vehicle not run properly, became a major issue about 5 years ago. About 20% of the store brand are dead right out of the box in my experience.


-Anyway I don't know how you reset the ECM but a sure-fire way to do it is to take a small wire & jump it from the disconnected negative(-) cable to the attached positive(+) cable as to assure the battery itself is out of the circuit.
Turn on/off the headlights momentarily & then leave the wire attached for 2-3 minutes, this will drain the ECM's capacitors entirely.

That is actually necessary on Fords in order for new idles to be learned properly. Typically done with a scan tool of course.




-The hanging RPM when you're coming to a stop is completely normal, Ford tuned it to be that way so that in the event you have the HVAC/radio etc cranked up, the engine wouldn't try to stall as you stop.
I know a lot of guys have installed IAC restriction plates to counteract that but it can have negative side effects, even stall, with an OEM size alternator, similar to under-drive pulleys.

-The P1443 could be anything from your gas cap to your purge valve and everything in between, I'd start by replacing any suspect hoses, followed by an OEM gas cap as vacuum leaks can set that code.

You mind telling me how many grams-per-second this new MAF is reading @ 1000rpm? I believe you had a malfunctioning MAF as well as one or more vacuum leaks that have become worse.
I'll be honest: Every vehicle 7+ years old has small vacuum leaks, just a game of time as to when they affect performance.