Idle issues

[Nomad]

I hope someone can help me. This is driving me nuts!
I have a 96 mustang gt with manual trans. It's dying during deceleration. I thought it was a faulty IAC because it went from every once in a while to all the time. I put a new IAC on it and it did not fix the problem. I went through the idle relearn process and it still dies on deceleration. When started it idles fine. If driving in grandma mode it idles down fine. If I engine brake then pop the clutch in it dies. I'm at a loss here. Why would engine braking cause idle down issues?
I checked for vacuum leaks and found none. I cleaned and inspected the throttle body. What else is there? It only does it if you hit the clutch during moderate to heavy engine braking.
Now... once the rpms dip to around 1000, if you blip the throttle it doesn't stall out. God I hope this makes sense to someone...

 

[96blak54]

Great explanation. Im assuming their are no upgraded engine parts and its otherwise all stock? Typically aftermarket parts come with associated issues that are over looked. I

 

[badass98svt]

Sounds like the VSS (speed sensor). It's mounted on the trans

 

[Nomad]

So it isn't stock. It has a pi heads, stage 2 street cam and the trans was swapped ti a tr3650. It was running fine until a few days ago.

 

[Nomad]

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[Nomad]

It's funny you say that... the speed was off after the trans swap. Then a few days ago I realized that the speed cal was causing a battery draw. Since it wasn't an extended range, and there for the speedo was way off anyway... I just unplugged it and now the speedo doesn't work at all... ill try plugging it all back in and seeing if it makes a difference

Sounds like the VSS (speed sensor). It's mounted on the trans

 

[ttocs]

how did you check for the vac leaks?

 

[badass98svt]

It's funny you say that... the speed was off after the trans swap. Then a few days ago I realized that the speed cal was causing a battery draw. Since it wasn't an extended range, and there for the speedo was way off anyway... I just unplugged it and now the speedo doesn't work at all... ill try plugging it all back in and seeing if it makes a difference

Yup, that definitely sounds like the VSS. Swap it out. Takes less than 10 minutes.

Definitely not a vacuum leak.

 

[Nomad]

Well... the problem I have is that I'm running a tr3650 trans in a vss car... so I can't swap it out. And dalas mustang is no longer in business so where are you guys getting speedo calibrators from?

 

[07GtS197]

Abbot era

https://lmr.com/item/AEI-ERA/abbot-mustang-electronic-speedometer-recalibrator-era-94-04

 

[Nomad]

I wanted to update the thread just incase someone else has this issue. Car runs great again. It was 100% the vss. I plug everything back in and that was it.