Severe miss-firing under load

You’re still just looking at a whole bunch of possibilities.

However, the difference between cold and hot is the difference between the engine operating in “open” vs. “closed” loop operation. During open loop the PCM runs a rich fuel mixture (the equivalent of what used to be the “choke” in the days of carburetors). After you get to operating temp it goes into closed loop which means it will be adjusting the fuel air mix based on info from the oxygen sensors.

One primary input will be the coolant temperature sensor and if it is bad it will leave you in open loop & leave the car running too rich. (A stuck open thermostat could did this too, but that would be accompanied by other things like poor heating inside the car). The other thing is that O2 sensor issues will throw off the PCM in terms of making the optimal fuel/air mix.

The thing is that the entire story can get complicated. So the engine temp issue suggests some possibility that you’re having this kind of problem. But it could be that you still just need new plugs or fuel filter etc.

Either way certainly give the mechanic the info.

THATS the kicker …those back plugs…NO ONE DOES THEM…they say they do…but most dont. Bet you have a bad wire on the “back 3”


I would bet it is a bad wire (or more) or bad plugs.

Would cylinder 1 be on the back?

Look at the two heads and valve covers. One of them will be about 1/2 inch closer to the front of the engine than the other (it has to be due to the width of the connecting rod and bearing on the crank). The cylinder head that is closer to the front of the engine has cylinder #1.

…and just to elaborate a little on what JoeMario said, in case you don’t know, the front of the engine faces the passenger’s side of the car. I.e. the engine is in there sideways. You can also probably go to Autozone’s free online repair info & find a diagram for the firing order. The plug/wire numbers might also be printed/stamped right on the coil pack.