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...

Sounds like you might have a catalytic converter problem or an issue with the fuel pump.

Welcome to NICO!


-Ben

It is definitely NOT the cat. If it were the fuel pump, why would it only do it once it warms up to operating temp? I doubt it is the fuel pump. I am going to try cleaning the throttle body and MAF sensor to see if that helps. If not, then I'm thinking possibly the O2 sensor or some other sensor. How should my van respond if I disconnect the O2 sensor after it has reached operating temp and went into 'closed loop' mode?

Please tell us what fixed your problem. I have the same exact issue when the car warms up it runs terrible.

markf1971 wrote: How should my van respond if I disconnect the O2 sensor after it has reached operating temp and went into 'closed loop' mode?

it will revert back to "open loop" mode... running off the preset factory specs that is in the vehicle's ECU/ECM

if disconnecting the sensor makes it run better, that may be the problem.

even with no CEL coming on, suggest checking for codes anyways...

waitamin, deja vu!

3-0l-runs-rough-when-warm-t407021.html