6605stang

So the saga continues....

Was going to take it into a local shop today so last night I decided to do that last few things that I could do myself to try and troubleshoot.

1) took off the CAI and cleaned the TB fins. There was some mild film on them, but nothing crazy.
2) cleaned the MAF with MAF cleaner.
3) changed the fuel filter

Fired it up and while it didn't throw a code immediately (it never does immediately), I noticed the same AFR "searching". At idle it would then go tick back and forth between 14.9 and 15.0, consistently... like pendulum... up and down and up and down... and you could hear the engine doing "something" at the same rate... up and down.

So I decided to try and swap tunes... I don't know... I was fishing... I have always run the Jon Lund tune and swapped it for the FRPP tune...

The FRPP tune immediately settles out to 14.7 and just sits there...

I decide I want to see if loading the Lund tune back NOW, would make any difference, so I loaded it back... same thing - settles out to 14.9 and starts ticking back and forth between 14.9 and 15.0... back and forth and back and forth. I give up and go to bed.

NOW... this morning... I fire it up, warm it up and take off for work... NOW is notice that the idle is ALL F'd up! When I engage the clutch, it hangs at like 2200 rpm?! Then SOMETIMES it will idle down to like 700rpm... but mostly it just sits at 2000-2200 and hangs there... WTF? I finally get to work and in the parking lot it settles down to about 1250 rpm and idles there. I turn it off and start it back up and it settles right down to 700... ok good. Then I give it some throttle and it settles to 1250 and hangs there...

WTF have I done and WTF is going on!!?!??!?! Is it possible that a tune can go back after using it trouble free for 4 years?

Does ANY of this make ANY sense to ANY one?

I hate to even take it into a shot like this have some stranger start tearing EVERYTHING apart hunting this Gremlin...

Simon1

To me, both of the idles you described are pretty normal for our cars.

The "doing something" probably counds like a miss or stumble. Also normal for cars like ours.

The hanging idle could be adaptive learning still settling things out. But I lean towards needing a little bit of fine tuning the driveabiliy features of the tune.