88’ 2.9L V6 engine dies after getting off of highway

[SvenLaxMan]

Hey looking for a diagnosis or some insight as to whats up with my truck, she died out as soon as i started coasting in neutral on the off ramp, but started up fine after a quick rest at the red light, i was then able to keep it from dying out again by just giving it a little gas

 

[RonD]

IAC Valve most likely

On cold start does it idle at 1,100rpms or so, then idle slowly drops as engine warms up and settles in at around 700rpms after 5minutes(full warm up)
This would mean ECT sensor and IAC Valve are both working
If this doesn't happen the IAC Valve could be stuck
You can clean it

But can ONLY replace it with Motorcraft or Hitachi brand IAC Valve

 

[dirtymike]

This is the way mine warms up, and to the second it seems. It idles down in three steps. I still have the original Hitachi brand IAC Valve (Thanks for the tip @RonD) and it works perfect. I clean it out every once in a while and test it and it operates smooth. Good luck finding one. If I find another one ill pick it up fast. The ECT sensor is something i test first before i replace it. Ive had some send a (ohms) signal of a -40 degrees temps to the ECU. Runs rich and idles high. Dirty

 

[SvenLaxMan]

IAC Valve most likely

On cold start does it idle at 1,100rpms or so, then idle slowly drops as engine warms up and settles in at around 700rpms after 5minutes(full warm up)
This would mean ECT sensor and IAC Valve are both working
If this doesn't happen the IAC Valve could be stuck
You can clean it

But can ONLY replace it with Motorcraft or Hitachi brand IAC Valve

So my truck starts up like that, almost to the letter, but this morning it wouldnt start up at all. If its not the IAC valve then do you have any other ideas?
Ive been having this problem intermittently every few months, it always starts with a subtle jerking while on the highway and the Results in dying out as soon as i go into neutral. It will either not start up at all afterwards (which is the case today) or it will just kinda go away. Ive had it taken into shops and they had no luck figuring it out either

 

[RonD]

Next on a 2.9l would be TFI module issue, very common for these to get heat sensitive, so it heats up on the highway and then when you slow down air flow in engine bay is less and it gets even hotter for a moment and a no spark stall
And a no start until it cools down a bit

Article here on that: https://www.therangerstation.com/tech_library/TFI_Diagnostic.shtml

 

[SvenLaxMan]

Next on a 2.9l would be TFI module issue, very common for these to get heat sensitive, so it heats up on the highway and then when you slow down air flow in engine bay is less and it gets even hotter for a moment and a no spark stall
And a no start until it cools down a bit

Article here on that: https://www.therangerstation.com/tech_library/TFI_Diagnostic.shtml

Thank you so much this will be super helpful! So this morning starting it up it was cold, hadnt been started in at least 8 hours. It would turn over but sounded like it there wasnt enough fuel or something and just wouldnt run. Do you still think it could be the TFI module?

 

[RonD]

Could be its now just dead, lol

But do 50/50 test to see if it starts
Spray fuel into the intake manifold, gasoline, ether, carb cleaner, ect........
Try to start
If it starts runs then dies, spark is working but fuel injectors are not
If it doesn't fire up very well, or at all, then Spark is the issue
50/50 instant results