OK, since nobody has replied to this, and others are having the same problem, I'll tell you what I found.
I have a Sport Track XLT 4WD 4L.
The intake manifold seals were hard and leaking air.
There were a few other vacuum leaks that I fixed by buying new vacuum hoses.
Doing the intake manifold seals is a bigger sized job, b/c I took the entire top end off down to the heads.
After putting it back together, i did and did a total tune up on it.
While in there I replaced the thermostat housing and all that hoses, sensors and seals.
In fact, I replaced every seal that I could, and think I got them all.
There's NO KIT for this job like in the olden days, like what FelPro would provide.
So you have to PIECE IT TOGETHER one seal at a time.
Also, I got the injectors cleaned professionally.
Every vehicle needs that done at least every 80k miles.
Now it runs like new!
Lots'a power!
This is how I figured out there were vacuum leaks:
I built a 'DIY' SMOKE GENERATOR.
I made my own for about $35.
Got the plans off of eBay for $5.
A smoke generator pushes smoke into the intake/EGR system, and if you have leaks, they will show up as smoke leaking out.
The smoke can leak out anywhere around the engine's top end, it can leak out of the exhaust pipe (if you have any bad valves) in the head, it can leak out of the EGR and EVAP system (can go all the way to the gas tank area!), and it can leak out of the oil fill (if you have bad rings). The SMOKE GENERATOR is an AMAZING tool if you know how to use it and look carefully to the results of using it.
I usually hook up the smoke generator to the brake vacuum hose (the one that goes to the brake booster), and also plug the intake right at the throttle body opening (a plastic bag with rubber bands). You hook it up to your battery and wait for about 15 minutes to a half an hour. I PROMISE, if you have leaks (even tiny little leaks!) they will BILLOW SMOKE! You may need a flash light (I use a head beam) to see where the smoke is coming from in dark areas like behind the engine or under things.
Once you find the LEAKS (if you have them), then you can figure out what you have to do to fix them.
The SMOKE GENERATOR is my GO-TO TOOL when doing RUNABILITY diagnostics.
If you want to take a crack at this, try looking up on the Internet "DIY SMOKE GENEREATOR".
Here's a page I found:
DIY smoke generator - Google Search:
Mine is made with a paint can, inlet + outlet plumbing (compressed air regulated to 2 psi MAX!), nichrome wire with insulated connectors, wrapped around a tiki torch wick (inside the can), and about an inch of mineral spirits on the bottom of the can, which makes the smoke when the nichrome wire heats up red hot (but doesn't ignite the mineral spirits). The nichrome wire hooks up to your car battery.
If you 'smoke' your engine and don't find any leaks, then you really should look to see if you have any DTC's (trouble codes).
You really should'a done that first anyways!
That will get you going in the right direction.
I also found the IAC to be a problem when it stalls while coasting, or for no other reason when stopped or going down the road. The DTC's for that were stupid when I checked them (they had conflicting advice in the OEM service diagnostics manual), so I just took a chance (educated guess) based on past experience and stuff I read in these forums. I found the IAC goes bad about every 50k miles.
Good luck to anybody who reads this!
