2014 Hyundai Accent GLS
I have replaced all 4 injection coil packs, all 4 spark plugs, air filter and the O2 upstream sensor. It still idles really rough and feels like it is going to stall. The original codes were 300, 301, and 302. I am assuming 301 and 302 were for the coil packs. 300 was a misfire code.....at Auto Zone.....for 300 it came up with possible fuel injectors and O2 sensor as the most likely. The other things it could be that are only 3-8% of the problem are: throttle body, engine fuel system, positive crankcase ventilation valve, fuel injector and knock sensor. Most likely maybe throttle body? I saw your video on the throttle body and cleaning it. Should I start there or do you have any other ideas? I really don't want to spend huge amounts at the mechanic.... this car seems pretty simple to maintain and take care of. A little more information: I picked this car up for $500 from a guy who hasn't taken care of it the last few years. He was driving around town for the last year on injection coils 1 and 2 being bad. The car feels like it's gunked up and choking. So, your ideas of cleaning valves and such make sense to me. Please help!
A full diagnostic scan would likely reveal some useful information. In the meantime it would not hurt to clean the throttle body and MAF sensor, and check for vacuum leaks as well.
HI Chuck. Do I have to wait 50 miles to scan since I just did all this work? And will I make the car worse driving it?
Thank you for your help.
Do I have to wait 50 miles to scan since I just did all this work? And will I make the car worse driving it?
You can scan for codes and live data at any time. There may also be useful freeze-frame data stored.
If the engine continues to misfire you will likely damage the catalytic converter, and over time may damage the engine from unburned fuel being introduced into the cylinders. However from your initial description it sounds like that may already have happened due to the previous owner driving for an extended period that way.
Also see the site FAQ for information on diagnosing misfires.
Okay great! I am hopeful it isn't the engine.
A quick compression test will tell you if there are any serious internal problems and a back pressure gauge can check for a clogged catalytic converter.