P0300 code

Tiny
TOBASCO22
  • MEMBER
  • 2002 MITSUBISHI LANCER
  • 2.0L
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 120,000 MILES
I recently had a p0421 and a p0300 code pop up. I got both oxygen sensors and the catalytic converter replaced about a week ago. The p0421 code is gone but the p0300 code came back along with the car having a rough idle, shaking when driven, and losing power to the point that the car will not go over 40 mph. The spark plugs, coil packs, spark plug wires and PCV valve have all been replaced and the timing belt and battery are under a year old. Fuel injector cleaner was run through the car just in case it was a clogged injector. I also noticed the PCV hose was cracked so that will be replaced shortly(though I don't think this is what is causing the code. Are there any other reasons the car would be giving me this code?
Tuesday, June 18th, 2019 AT 2:06 PM

1 Reply

Tiny
SCGRANTURISMO
  • MECHANIC
  • 4,897 POSTS
Hello,

A cracked PCV hose will indeed cause this DTC. That will cause a vacuum leak, and vacuum leaks will cause a number of idle related issues from a searching idle to a high idle, to a rough idle, or all the above. It probably wouldn't hurt to check your air intake tract, from the MAF sensor to the combustion chamber, including intake manifold, throttle body, air duct, vacuum lines, and EVAP lines. I have also included a link below for you to go to:

https://www.2carpros.com/articles/engine-vibration-at-idle

Please go through this guide and get back to us with what you happen to find out.

Thanks,
Alex
2CarPros
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Thursday, June 20th, 2019 AT 7:05 AM

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