Ok, well here we go again with one of my friend'* fords

This is a 1989 Mercury Grand Marquis LS with the 302.

It will run fine when its cold and runs strong and smooth, but when it gets warm, it stutters, misses, and surges. And if you put it into gear without holding the RPMs up with the accelerator, it will stall.

Heres the huge problem. It barely moves. I mean once its in gear, its ok, but like if you go like from a stop sign, it BARELY moves. Like, absolutely PEDAL to the METAL it will barely get to 40.

When we got it going, something was seriously wrong, the exhaust got SO hot, that the insulation above the cats was smoking. Like, nearly on fire. We looked like a fireball going down the road.

What could be the possible problems? Before it sat for nearly a year to rebuild the engine (don't ask), it ran fine!!! It got rebuilt because of a little piston slap. And a couple other things. But otherwise, fine. We're all stumped. the guy that rebuilt the engine recently recieved his ASE certification, and he knows he didn't screw anything up.

Help please!

My first guess would be a leaking or misrouted vacuum line, since both systems listed are vacuum based.

Clogged catalytic converter FTW. All your symptoms point to it. Get it checked.

if the cats are getting hot.... plugged cats.... maybe....

*edit* damnit Wren, you beat me to it

unhookem and run it if it runs strong you know your problem is deffinatly the cats. even though it is its fun to hear a open manifold 302 everyonce in a while

It could also have an issue when it goes into closed loop. (warms up)
That could be an O2 or MAF.

An old O2 can kill a cat.

That should be a 4-wire O2 sensor.

Check the coil as well. Mine went out on my truck and I saw similar symptoms

I was thinking cat too...I messed with this 89 Cougar that had clogged cat issues...and it had 2 cats, one for each bank IMS.