Ok guys heres a beauty of a question; Recently about 4 months ago my opti went south so I put one in along with new plugs-wires-new coil and 160 thermostat. Now here it is when the car is below 180 degrees it runs like a monster; when the temp goes above that and I punch it, it surges-misses and stumbles like crazy. Today my heater core went out on me and started pissing out like mad so I bypassed it (spring is in the air in Spfld, Ma) my question is Why is it stumbling hot but not cold? Also the fans do not kick in until its almost redlining to overheat? Also when it starts to stumbel my tach starts to act erratic and jumps up about 1,00rpms? I know my cat is no good because it makes rattling noises. I put in a new fuel filter as well Someone help as it is getting warmer out and I would hate for a civic or a prelude whip me into shape!!

 

Start with the basics. See if any codes are stored in the computer. Beyond that it sounds like something to do with closed loop mode. Does this only happen at WOT or whenever it's warmed up?

 

Sounds like the coolant temp sensor by the water pump is toast.

Just a guess.

 

just when she is completely warmed up and there is no stored codes either

 

I would check the temp sensor like Grip said and also check the O2 sensors.

Kind of wierd though no codes

 

My cat makes rattling noises while I am idling and when I replaced the exhaust I noticed it more clearly like the charcoal inside was loose, that does not mean it is plugged, does it?

 

It sounds like the honeycomb material inside the cat broke loose, I had the same thing happen to one of my FLP cats. You should look into a high flow cat or an offroad pipe, that cat will need to be replaced.

 

Something electronic... The heat is the givaway. Look for arc burns on the plug wires, poor connections on the coil to start. Unusual not to throw any codes. Perhaps a gas line is too close and the fuel is evaporating. Could be any one or more of a million things.

 

Funny thing, I just replaced the heater core today and it was 68 degrees here and I watched the temp only go to about 180 for the day!! So I guess the rapid heating prob is over but it still doesn't explain the gremlin at above that!