I have a 97 Subaru legacy and my CEL stays on took it to auto zone but no codes piped up. My engine has been acting up really rough idle and no power at all. I shut it off and start it back up and it runs fine for about 15 minutes and does it again. What could this be?

odd - try another shop to read the ECU.

 

maybe do a battery disconnect and see if it clears the CEL?; remove neg. batt terminal, step on the brake pedal to remove any slight residual charge, wait a few minutes, reconnect.

I've tried 3 different places and they all say the same thing. No codes had it reset and it comes back on after about 20 miles

very odd, never read of something like this I don't think. any other strange behavior?

 

is the car new to you? any work, mods done or wrecks before this started?

 

you may need to get freezeframe or live data. If you have a smartphone or a laptop, there may be inexpensive ways to get data from the car yourself.

It's new to me, it ran fine until I charged the battery and put a new terminal on it then the power loss and violent shaking came. It doesn't make sense to me either. Especially when I shut it off and start it again it goes away for about 15 minutes.

hmmm....15 minutes of running well.

 

Is that reliable whether hot or cold? That is, If the engine is fully warmed-up, you can turn it off and immediately back on and it runs well? Or, if it only runs well if the engine is cold, could be engine temp sensor is misinforming the ECU which is keeping the engine 'choked' all the time as if cold.

Hot or cold it doesn't matter, engine shakes no power at all then stalls start it back up and runs fine. I'm familiar with cars and I've never experienced something like this

I think your ECU is bad. That's the only reason why I can think the CEL comes on but no codes are stored.

Yea I'm starting to think the same thing