94’ SN95 - Intermittent lope & bogging at moderate rpm

[Red5.0ho]

Recently got a convertible 94’ Mustang GT (automatic) as a trade and it’s been a bit of an interesting ride so far..

Upon looking at the car it’s in great shape. Zero rust to be found on this thing anywhere, the top works, and all the interior plastic is still in pretty good condition. Essentially stock aside from some BBK headers with an exhaust that currently dumps out underneath the car, double din radio, and an EGR delete.

So far I’ve done a front end rebuild, redid the stereo connections, installed new plugs, and a new coil. Nothing too major, just some basic tune up stuff for peace of mind. But this is when I started to notice what problems I’m actually dealing with

First: I checked the transmission fluid only to find that it wasn’t red but a dark amber brown, and without a doubt overfilled by whoever serviced the car last.

Second: The car Boggs down under moderate rpm. It varies between a bogging down effect and slight surges in rpm, as if it’s trying to guess what it’s supposed to be doing. (I’m guessing this is going to be due to a bad/dirty air sensor or vacuum leak)

Third: The last thing I’ve noticed is it will randomly lope at idle sometimes, and idle just fine other times. I’ve been noticing it does it more often on cold starts now that it’s getting colder out. But it sounds like the car will lope and progressively increase rpm’s slightly until calming down to the initial rpm

I like the car a lot aside from these few things and do want to get it running the way it should. Anyone with SN95 experience that could chime in on this would be a huge help!
I’ll post what codes are being thrown for better context tomorrow

 

[Red5.0ho]

Update: Attempted to drain the excess fluid but it looks like ford didn’t include a drain plug on these transmissions. So in an effort to avoid dropping the pan, I ended up just siphoning out as much as I could through the dip stick and then topped off what was needed with clean Mercon V.

Took it out for a test drive.. After putting it into drive it still takes a while to feel the transmission engage (reverse or drive) and it shifts at a higher rpm. May try adding Lucas to see if it helps at all, just hoping it’s not needing a full rebuild or replaced.


But after a bit of research I know there’s a few things I could check/replace to ensure everything in line before combustion isn’t causing one of the symptoms. So I’ve pretty much narrowed that down to:
-Vacuum lines
-Distributor
-O2 sensor
-MAF
-IAC
-TPS

If you’ve seen any of these issues with an AOD/AODE transmission or know what may be causing the strange idle/surge, please feel free to chime in

 

[General karthief]

First, as always, check for codes, next check ALL the vacuum lines, they are old and brittle.

 

[Red5.0ho]

First, as always, check for codes, next check ALL the vacuum lines, they are old and brittle.

I tried checking the codes but I’ve only got an obd2 scanner on hand, which gave a code read error. So I ended up attempting the koer test to count the amount of times the CEL flashes, but the light stays on when conducting the key on reading

I looked over all the vacuum lines and everything looks fine, but still need to try smoke test or engine on spraying starter fluid around hoses

 

[AeroCoupe]

Just get one of these and try the codes again.

Amazon.com

You can build a smoke machine and use that to find any vacuum leaks. I built one like this and it works great.


View: https://youtu.be/crc6CJ_ni2w?si=WXuOSTlLS4bivO52

 

[General karthief]

^^^^this^^^^ (or that, depends on your time zone) and I'll add....
To get a real idea of what your 35 year old vacuum lines are really like you gotta pull the upper intake and do a check and replace all the vacuum related stuff down to the PCV/screen/grommet as needed.
I bet you'd be surprised.