I have a 94 civic coupe. Most of my driving is city and for about 8 months the fastest sustained speed I was able to drive at was 50-60 mph. I got on the highway last week and was keeping up with traffic running above 70 for a few a few miles and when I pulled onto the exit ramp the car idled like crap and shut down. it started right back up but idled poorly and shut down on me another few miles down the road. It ran normal then a week passed and I went on the highway again and when I exited the idle dropped too low and I had to rev in order to prevent stall. any idea what is causing this? Too long creeping around at low speeds/rpms and maybe I blasted some deposits out of hiding when I opened up on the highway?

 

Any cel's on? Maybe your cat is plugged up? if you look underneath after driving for a while is the cat extremely hot?

 

my car never throws codes... ever. I honestly dont think it has ever thrown a code since I got it 6+ years ago. Someone told me that is not unusual though. I didnt think to look underneath at the cat. That could be possibility. I have noticed a slight decrease in power but have attributed that so far to the 160,000+ miles on it. What else would signal a bad cat besides low power (as I have had in the past with bad cats)? Fuel mileage seems consistent and I would crap a brick if my car spit a code. This hasnt occurred again( knock on wood) but I have not been on the highway or any other sustained high rpm conditions to spur it.