My mechanic just called (my civic is still in the shop) and he still can not find out what is wrong with it. He took the CAT off and it was melted inside. He said he had never seen a CAT melted like that before. His thinking is that the engine is running lean, which is why it stalls out when you try to give it gas to take off. But, he is not sure why it would be running lean/ what is causing it to run lean.


"New"(It was actually used) ECU didn't fix it, he put in a new fuel filter, checked the fuel pressure, he said my car does not have an EGR valve so there was not one to check.

I think it seemed to run a little better when I put fuel injector cleaner in the gas tank before making the 80 mile drive with it to the shop


Do you guys have any suggestions?

 

now it's starting to sound like you have bad gas... especially if that fuel additive helped. I would drive around until that tank goes empty and then fill back up with some premium to aid with the pinging and compensate for the leftover bad gas (since you wouldn't run the car until it literally runs out of gas). If you can't drive it, drain the gas tank instead (into proper storage container!!!)... there is a drain plug on the bottom of the tank. Then go back to regular fuel next time you fill up. When you do this, make sure you go to another gas station, not the one that you may have gotten bad gas from.

 

Running rich or misfiring will overheat and melt your cat. Under those circumstances, too much raw gas goes through the engine only to burn in the cat and overheat it. It is going to be hard to pinpoint when the melting occurred though since your car has been running badly for a while.

 

I think the bad gas possibility is ruled out. My mechanic mentioned that to me, but it was quickly ruled out because my civic is my daily driver and the gas that I have been putting in it has been coming from several different gas stations which I had been using while this issue was progressing, 3 I can name off the top of my head. He told me that if it were running lean, after stalling and me trying to restart the car, the excess/flooded fuel would dump into the cat and catch fire.

A friend of mine suggested these possible causes:
Leak in the air induction system
Clogged fuel injector
Bad/Dirty mass air flow sensor
low fuel pressure (mechanic already checked and said it is fine)
Clogged fuel filter (mechanic already replaced)
Exhaust system leak
Vacuum leak
Bad O2 sensor
Cracked PCV hose

Do any of these seem likely?

 

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