Alright, peeps i really need some help with this stupid car of mine. 😆. I have done everything in the book to get these codes off and have the car running. I've change the spark plugs, cap and rotor, wires. I've had mechanics look at it and can't figure it out. One of them said it could be the head gasket but I don't know if I believe that to be honest. We had them do the valve adjustment. The cars runs really rough. Do you have any other suggestions that I can do? 1998 honda civic ex. I feel like this car is my unicorn. 😄

 

you did a tune up and had a mechanic look at it who adjusted the valves (not a bad start) and then took a wild guess at bad head gasket?

I suggest literally going by what the book says and troubleshooting the P0300 step by step until you find the cause.

Don't spend that much (in the link) by the way. these manuals can sometimes be found as a free PDF, but if you want the hard copy I'd look for a good used one and expect to pay $80 or so.

A specialist or mechanic with lots of specific experience will do it faster, but any decent mechanic will have access to this same troubleshooting procedure/info and most of the tools required to complete it and offer a reasonably confident diagnosis.

 

If you leak down test all the cylinders you can learn if it is a head gasket issue.

 

Sorry i shouldve have mentioned that we replaced the engine because of the issue with the codes. We kept the same intake that was originally on it with the new used engine. On the replacement engine i keep getting the same codes. Hopefully, that makes sense. He did say that it was percolating back up the radiator when he diagnosed it but his price was ridiculous. I paid 400 for that stupid mistake and wont go back to him. I just don't get why it would run so rough even with a head gasket issue. I have ran that car before with a blown head gasket on the old engine, and it was just smoke coming not running rough.

 

do a search, I wrote a post about those codes