Q: Car is running very roughly at idle

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The other day I was driving home and the car lost power, and sounded really rough. Now, when idling it is running really roughly. I haven't tried driving it anywhere. The car is showing these codes: P0304, P1137, P0300, P1599. I am trying to figure out if this is something that I can fix, or if it needs to be done in a shop. I also need to know if I am risking damaging the car if I drive to a store for parts. I really need this car for work, and I have a long commute. Any ideas?

Hi there, thanks for writing in. Based on your faults, it seems as though you are dealing with a potential misfire causing the fuel mixture faults or fuel mixture problems causing misfire faults. The car should not be driven like this, as it can cause damage to the catalytic converter.

This is potentially something you can fix, but you’ll need to be mechanically inclined and have all the correct tools, including a compression tester and a fuel pressure gauge. Either way, the first step would be to perform a fuel pressure check and a cylinder compression check. You should also check for spark on cylinder number 4. Be careful when doing this because there is a risk of shock and of fire if any fuel was released during the fuel pressure test. These tests should point you in the right direction to diagnose your running issue, whether it be a problem with spark, fuel or compression. If these tests are beyond your scope, you should contact a professional to come to you and diagnose your rough running issue.

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