Orbiting234

Kind of an odd stall issue has crept up on my 1997 Taurus GL 3.0L V6 with 65k miles on it.

Short story first since it may or may not be related: A few months ago, I unexpectedly was getting hard shifts one day to the point of nearly barking the tires when it upshifted. Got it in ASAP and found out that the PCM decided to stop reading the TSS completely. TSS was fine, wiring to it was fine, PCM was just being flakey I guess. Got a replacement used PCM installed and all seemed fine.

But now that it's getting cold out, I'm experiencing an issue where if it's <30 degrees out, it will stall out upon moving it into gear from a cold start. If I just give it the slightest amount of gas while moving into gear, it's fine. Also a warm engine doesn't do this.

So could it be a bunk PCM I got and/or improper calibration codes in it? Or should I be looking somewhere else entirely like the EGR or IAC valves?

SHOZ123

The PCMs seldom go bad.

I would be looking at either the MAF being dirty or the IAC. Clean the MAF first.

tbird100636

I'd look at the throttle body first along with the IAC valve. When you replace or reset a PCM all its stored values are cleared and it basically starts from sqaure one assuming it has a clean throttle body. With the throttle body dirty the IAC ports are partially restricted and causes the engine to stall. The PCM will not adjust for this right away and you will continue to stall out for a long time. Here's what you do.

1. Remove the throttle body.
2. Remove the IAC valve.
3. Inspect the bore and the IAC ports of the throttle body for sludge buildup. Also look at the IAC valve chamber for the same.
4. If it's dirty clean it using carburetor/choke cleaner. Carb clean is safe to use nowadays. Before cleaning remove the TPS because the cleaner does have a unique effect on the TPS. Clean the throttle body with the cleaner, scrub the throttle body with an old toothbrush to remove the hard stuff. Carefully clean the IAC Chamber too.
5. Reinstall the IAC and TPS on the Throttle body and reinstall the throttle body. Take the car for a ride after and see if the problem is solved.
Good Luck!!!