'98 Ford Windstar stalled when switching from reverse to drive

So I was backing out of a parking space a few days ago, then when shifting from reverse into drive my car suddenly stalled, radio still worked but the engine was out. So I put my car into park, turn the key all the way off, then start my car again, and it cranks for a few seconds longer than normal before starting up again. It happened once more doing the same thing, backing out of a parking space and putting the car in drive, but I've listened closely and I feel like it wants to die at times however it never has. In the past I panicked a little and gave it some gas right as I'm shifting into drive from reverse just to see if that helps keep it from dropping in rpm's.

I've also recently just replaced the starter and battery and the car has had no trouble with that since. I've also noticed sometimes after having just turned on the car and I'll be sitting at a light or stop sign, the car will sort of "pulse" on its rpm's every now and then.

Do you think this is my IAC going bad?

Will I need to replace that or is there something else amiss?

Money is not something I have a lot of so I'm hoping this is a simple fix I can manage at home. I also am not 100% car savvy nor do I have a whole lot of tools to work with, but I managed to replace the starter okay.

I've noticed the same problem recently. I haven't really looked into it yet, so I don't know the cause, but I've had the same suspicion that you are (IAC). In my case the vehicle would drive in reverse down the hill of our driveway, but stall when stopped on a level surface.

I also had an odd misfire problem at the same time that I noticed stalling, so I thought they might have been related. I did some work on the vehicle and may have eliminated the misfire, but the stalling in reverse persists. I'll know in a few weeks if the misfire has been resolved.

Another thing to look for is the condition of your engine harness. Once our Fords gets some mega-miles, the insulation is often worn at the various connectors about the engine compartment. As the engine heaves as we go from drive to revers, or just braking, ... we may lose a signal for an engine/cam/crank sensor. This can be enough to snuff out the engine unless the revs are high.

Often a bit of clear RTV will strengthen the harnesses near the connectors.

I'm going to follow this diagnostic to see if the problem is the IAC:

https://www.yourmechanic.com/article/how-to-check-an-idle-air-control-valve-by-jerel-lawrence

IAC is a very common cause of this problem.
First, remove it and squirt some lubricant into it....SeaFoam in the spray version works.....flush out any crud with it.

IAC is a very common cause of this problem.
First, remove it and squirt some lubricant into it....SeaFoam in the spray version works.....flush out any crud with it.

I was reading on the SeaFoam's page that sometimes when applied to an engine using VVT tech that it can cause issues. the '98 Windstar GL 3.0 3dr doesn't have VVT right?

I also read that seafoam can possibly be corrosive to any protective coating/lining in there? Is that true and should there be something else similar for me to use instead if this is the case?

Seafoam used as I have mentioned will not be an issue.

Seafoam used as I have mentioned will not be an issue.

So, I have to wait to get paid to do anything for the car, but tonight, driving home, my car was chugging sort of, and the CEL came on and was blinking all the way home. Barely limped her into the parking spot at my apartment. Is this another factor of the IAC being dirty/going bad? :( Why does this have to happen when I'm the most broke. I stg.

I don't think the IAC would cause a severe misfire under power unless it practically fell off. You can make sure it is secure, but I check the diagnostic codes if you can. My guess is that you have either a problem with the spark, fuel delivery, or a valve/compression problem.

Also, I stopped having problems with stalling in reverse when I repaired the velocity speed sensor connector. It was very loose due to deteriorated plastic, and possibly making poor contact when cold). It got bad enough that it was getting erratic shifting (e.g. up shift when approaching a stop sign) and set a diagnostic code.

I'm convinced that my transmission was damaged and had to be swapped out before normal because of the occasional bucking and heaving of the engine. The dealer, of course, could not find anything. The problem got so severe, I committed to find the problem or never drive the Winny again.

The drive train harness around the engine had to be removed before I found the damaged insulation on three conductors. All were bouncing off of firewall metal. No problem since repair.