engine runs ROUGH when warms up - HELP!

[markf1971]

I know it's not a true Nissan but it's a Nissan wrapped in Mercury clothing.

I have a 93 mercury villager minivan, 3.0L auto, which has been pretty dependable for all my needs.
I'm at a loss as where to start looking for a solution to this problem.

Here's the scenerio:
Engine runs normal when first started (cold), but as it heats to normal operating temperature (about 15 min.) it begins to run VERY VERY rough.

At this point it starts sputtering, coughing and the vehicle becomes inoperable (no power, backfire and will not get past approx. 10-15 mph) and will not run smooth again until engine cools.

At NO point does the CEL come on.

Now that's the part that is getting me, after it cools off it will fire up and run fine till it reaches normal operating temp again.

I's obvious to be temp related but what?

I have replaced the plugs, cap, rotor, wires, & fuel filter…. All of which needed doing, but none of which have helped my problem.

I sure would appreciate any help anyone can give.

Thanks in advance...

[Ziggy1621]

I would check your oil for any water in it before running it again. Then, I would check around the head for visible signs of leakage. If you are getting too hot and the head has any play against the gasket, it can create a compression leak.

That's the only temp related power loss I can think of.