Car runs rough and check engine light is on. Runs smooth when AC is off

basically it runs rough and makes noise when AC is on. While it may not be perfect when off, it certainly is quieter. Check engine light just came on. any ideas? I am in Palm Beach county Fl.

The first step is to go to an auto parts store, such as Auto Zone, Advance Auto, O’Reilly, or (possibly) Napa, and ask them to read the trouble codes that have been stored by the car’s OBD system.

Then, come back to this thread to post the code(s) that are found. They will be in a format similar to “P0123”.

Once we know which codes have been stored, we can try to give you some specific help. However, until you tell us the model year, odometer mileage, and maintenance history of this car, we may be shooting in the dark.

That CEL (check engine light) is just a kid in class waving her hand trying to get you attention because she has the answer. You need to have the codes read. Some places will read them for FREE. Try Autozone or Advanced Auto Parts. Get the exact code (like P0123) not just their translation into English and post it back here.

ok the scanner gave a cyl 1 misfire. but it is pronounced when the AC is on and not when it is off however, there is an occasional hiccup

@hoops41…the AC just causes more load on the engine and a poorly running engine will run worse when a load is applied.

The only thing about the AC being on is that the compressor puts a lot of load on the engine. If things aren’t running quite right, then whatever problem(s) exist will make themselves known.

So your car is running poorly including at least one misfiring cylinder - that’s the bottom line. And no one will really know where to start without knowing the mileage and maintenance history. So all I can say is that you need to go through the car and do all of it’s basic maintenance. Misfires are often from spark plug and/or plug wire problems. If they’re anywhere near due, then just do them. The existing plugs should be “read” - inspected for clues to any kinds of problems. The fuel pressure should be checked and fuel and air filters changed. Stuff like that. If the plugs and wires get done and the misfire remains, the compression should be checked next. Start doing stuff and report.