NO power under load, backfires thru carb, overheats.

Oh, God, where do I start? 3.1l engine started misfiring, rough idle, shudder at certain throttle settings and loads. I changed the plugs with no effect, and then the wires, and lo and behold one wire was burned through. Problem solved. I thought. Three days later I was climbing a LOOOONG grade, down into second gear at about 4000 rpm's, when I suddenly started losing power and actually stalled out. Temp guage went up almost to the red and was blowing into the tank. After pulling over I was able to restart, and everything sounded ok, so I finished the climb but now the miss is back. Hmmm. On the trip back it had no power on the climb, and if I gave it the slightest bit too much throttle it started popping and backfiring through the carburetor(yes, it's carbureted!). When I got home I started checking the wires and plugs, and the center plug on the bank closest to the firewall was MELTED! Both the center post and the electrode were just gone, the insulator material was blistered, the base was blued and flakey, I've never seen anything like it. Anyway, I replaced the plug and tried everything again, and it's still missing. It will hardly go up the hill to my house, overheats when I try. I don't get get it. Today the water pump started leaking, but I'm pretty sure that's unrelated. Did I burn a valve or damage the rings with the melted plug? Gimme some possibilities here, folks.
Thanks! :confused:

Also, Who can tell me how to do an engine change on this thing? I got a 2004 3.1l Grand Prix/Malibu engine online with only 14000 miles on it, apparently a factory pull, but it isn't real obvious how to get the engine out from under the hood. Do I have to go out the bottom with the whole assembly, or maybe remove the radiator core support and come out the front? For what I paid for the engine I couldn't pay someone for a valve job(that's what I'm beginning to suspect).

On the second post regarding engine swapping, I assume this is the van, not the car. The engine must come out the bottom of the van, and you'll want a floor lift for this (jack stands just won't cut it).

Oh yeah...since this is a newer, injected motor, how much trouble is it to install the injection computer? Should I just change the manifold and put the carb on the new one?

If you want the newer injected engine, you'll probably have to bring all the electronics with it. When you take the engine out of the donor car, take EVERYTHING, and you'll have to be devious about where to put it all. Have fun!

What year is your car?
You've either jumped timing or its running WAY too lean. Extremely lean can cause no power, sputtering/missing, and overheating. How does it idle? Is it smooth or rough? Check your feul filter, and replace the o2 sensor.

The 3.1 was first used in '90 model year cars. And it was MPFI, never was carbed. In '85 they stopped using carbs. Its a throttle body.

It's a 1990 APV. There are two electric units on top of the downdraft throats, spraying gasoline into the throats. There are no injector lines, no injectors in the head, and a standard air cleaner, if this is injected I've never seen a system like it. I just replaced the O2 sensor. Yes, it idles rough, and the center cylinder on the firewall side is not firing. I think I just cracked the heads though, because yesterday I overheated very rapidly and the started blowing huge clouds of steam out the exhaust. This engine is toast. The replacement engine only cost 250.00, I cant get a valve job done for that price. I just need to make sure that the 2003 Gran Prix/Malibu engine will bolt up. If this is indeed injected I won't have to add the computer, will I?
Thanks Kooterskkar!

Aye, the TBI was used in the APV engines for some reason. I'm not sure the newer 3100 will bolt up to the old 3.1 cradle, but you can sure try. Because the 3100 is SFI, you will need the electronics to go with it...a simple TBI computer just sprays fuel into the throttle body, wheras the SFI times the injection pulses for the cylinder on the intake stroke. If you get the computer from the new car, it might not match up with your cluster or wiring harness. You'll need the harness and computer, not just the engine.

I figured it would be something like that....just the front harness? I've seen guys add injection computers to Jags getting the Chevy conversion, seemed kinda simple there. Anybody have any specifics? Otherwise I'll have to change the intake manifold and throttle body. I'd rather skip any unneccesary steps.

Junk the APV, and drop that 3100 right back into the Gran Prix. Trust me. (although I thought the newer grand prix's came with the 3800's??) Anyways, good luck.

check your coil packs for gunk built up on the post. also the ign module under the coil packs are known problem. Check them out before you swap an engine