random misfire P0300 code on Jeep Grand Cherokee Laredo 3.7L

Question

The check engine light (which does blink once in awhile) is a steady light). There is loss of power only when I first start the vehicle and then only seems to last say, for 3-4 minutes and disappears and full power seems to return - but the engine light stays 'on.'

For awhile, it seemed that the loss of power was more noticeable and severe when I first started the vehicle after it had rained the night before. This led me to think that somewhere, a wire connection was either loose or had a bad insulation . . but my investigation and even spraying all wiring connections in the harness under the hood has not resolved the issue. So, then, I've done the following with no change:

replaced the spark plugs (and even replaced otherwise good plugs); sprayed fuel injector cleaner around the manifold with engine running to test for any leaks; checked all hoses around the manifold area for cracks and leaks; I put my hand over the end of the exhaust with engine running, then removed it and smelled for a rotten egg type smell (re: bad catalytic converter). . . but, there is no smell at all; I added a can of Sea Foam into a full tank of gas, followed directions. A few days later, the P0300 code disappeared as well as the engine light and the car was running at full power. But, 3- 4 days later, the problem returned. So, I added a second can of Sea Foam and there has been no improvement- the P0300 code and the engine light remain.

I then, pulled and cleaned and electrically tested all 6 fuel injectors = good (injectors were not even dirty);

I have found nothing. I wanted to check and change the fuel filter but I understand not only is it located inside of the gas tank but it is part of the fuel pump assembly and cannot be serviced or changed separately. The fuel pump works perfectly fine. I'm flustered. . can you assist? thank you

Answer 1

Hi there,

Here is a list of all possible causes for a misfire. 

P0300 JEEP - Cylinder Misfire Fault Detected Random Cylinders

Read more: https://www.autocodes.com/p0300_jeep.html