'91 explorer runs sluggish when cold or under load

[schecterdude]

I bought a '91 Explorer (4.0L V6) a few months back and it had an issue where it ran sluggish when the engine was cold and then would run normally when I ran it for a couple minutes. For that issue I replaced the plugs and that seemed to fix it......until a couple weeks ago. Now it runs sluggish, from a cold start, when it's under load. It seems to run decently when I'm barely pressing on the gas but can't give it too much more before it starts to run like it's running on 5/6 cylinders. Again, it seems to get better as the engine warms up.

Other than the plugs, i've also replaced the spark plug wires and have ran a few courses of fuel injector cleaner through my tank.

On a side note, just in case this could be a cause to the problem, I currently am missing the exhaust system from the cat all the way back because it rusted off (good times).

Can anyone offer some suggestions to what might be causing this? Could it be an ignition coil?

 

[92exp4x4]

Could be any number of things. I think its running rich and fouling the plugs?

Start by pulling codes. Even though the check engine light may not come on, there could still be a codes in the system. Find out whats in there and start with that.

Some of the other basic maintainence procedures are:

clean MAF sensor, replace air filter, fuel filter, and PCV valve.

 

[modified]

check your grounds. also, consider your oil viscosity is much thicker in your engine when cold.

 

[tk1251k]

I had a similar problem as you say you are having. I thought all along it was vacuum related and had ruled out intake gasket but accidentally ran across the problem. I removed the large plenum where it conntects to the maf and it had 3 rather large holes underneath . Taped the holes shut and more cold idle problem.

 

[Reejerey]

could be a bad head gasket or really bad valve stem seals too, any smoke on cold start?