Hello, I was driving late one night and my Jeep started driving rough I pulled over and pulled up code p0300. Towed it to my house and replaced the spark plugs. Ohmed out the coil packs and they also seemed fine. Jeep sounded worse after replacing the plugs. Towed it to the dealership that took them 2 weeks to diagnose they went on to say the upper and lower manifold was cracked filter was clogged and how I drove through a lake. and it be a $1300 repair. They also said my new spark plugs were faulty and needed to be replaced when I commented on how they just been replaced they said they needed to go into further diagnosis. They came back a week later saying they were definitely bad and the price was actually gonna be $2400. I towed the Jeep back to my house and inspected the manifolds and found a crack in the top one not the bottom. Ordered a new upper intake manifold, new cold air intake, throttle body spacer, PCV valve and PCV valve hose. Replaced all parts. And now it will idle perfect for 5 minutes then the check engine light will flash and start idling rough.. what’s my next steps to try?
P0300
- Thread starter Jzm7337
- Start date
If you didn't use OEM parts that could be your problem, also check your battery clamps and grounds to make sure they are clean.
Upper intake was OEM but the PCV was not. And the air intake was aftermarket as well.