Misfires on start up, then evens out

CARALYN13

MEMBER
2009 DODGE JOURNEY
2.4L
4 CYL
2WD
AUTOMATIC
130,600 MILES

Hey everyone! I am completely stumped. I have misfire codes of P0300, P0302 and p0303. It starts rough on start up, then runs fine after that. Over the summer, it was overheating. After changing the two thermostats, and burping the system a couple of times, it seems to be okay. I also changed the coolant temperature control sensor. I have changed the spark plugs, coils, crank and camshaft sensors. Exhaust manifold had three huge cracks. Fixed that. No oil in coolant and no coolant in oil. Pressure tests were all steady. I am stumped. I do have a slight oil leak from the oil pan gasket, that will be fixed soon. The oil is never on the ground. Just kind of seeps.

I also want to note that I replaced the third fuel injector and cleaned the others. The third was the first misfire code I had received. The random and cylinder two followed after.

I need help. Any ideas?

5 Replies

KEN L

MASTER CERTIFIED MECHANIC
47,595 POSTS

This sounds like it can be one of two problems. first, you can have a head gasket that is just starting to leak coolant which is why it cleans out after start up.

Here is a guide to help you confirm the problem:

https://www.2carpros.com/articles/head-gasket-blown-test

The next is a leaking injector which will cause the misfire and clean out much like a head gasket failure.

For this test you need to remove the spark plugs and check for the one that is different in color (black or dark dray) this will be the cylinder that is having the problem.

Please let us know what you find.

Cheers, Ken

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Monday, September 11th, 2017 AT 12:22 PM

CARALYN13

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3 POSTS

Leak down test, coolant compression test, cylinder compression test cams back good. Spark plugs were checked. They still look brand new.

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Monday, September 11th, 2017 AT 1:05 PM

KEN L

MASTER CERTIFIED MECHANIC
47,595 POSTS

Okay, my next thought is the MAF sensor which if it has not been replaced would be a candidate becasue when it has that many miles on it the sensor wire becomes contaminated and will send a false reading to the computer causing a misfire like you have described. The only way to test this is to get a new one and read the live values between the the new one and old one to see if there are off from one another.

Here is a guide to give you an idea on what I am talking about:

https://www.2carpros.com/articles/how-to-replace-a-mass-air-flow-sensor-maf

Please let us know what you find.

Cheers, Ken

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Tuesday, September 12th, 2017 AT 10:24 AM

CARALYN13

MEMBER
3 POSTS

Would a battery starting to go out cause this as well? It take a minute to crank over.

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Tuesday, September 12th, 2017 AT 10:31 AM

KEN L

MASTER CERTIFIED MECHANIC
47,595 POSTS

If the battery is weak then yes it could as the engine struggles to find the voltage it needs to run.

Here is a test you can use that takes no equipment:

https://www.2carpros.com/articles/car-battery-load-test';

Please let us know what you find.

Cheers, Ken