Code 0300, multiple misfires?

ABUSTA33

MEMBER
2011 NISSAN TITAN
5.4L
V8
2WD
AUTOMATIC
136,000 MILES

Continue to get a service engine soon light and code of 0300, multiple misfires. I replaced plugs with NGK iridium, did an ignition test on all coils which all fire. I can hear the fuel injectors clicking with no abnormal sounds. I cleaned the MAF sensor and had an engine and fuel clean with BG product kit by a mechanic. Also, dry compression on cylinders is about 180-195. Clear engine light and once I drive and accelerate around 45 MPH after about 10 minutes of driving the code 300 comes back.

7 Replies

JACOBANDNICKOLAS

MECHANIC
109,885 POSTS

Hi,

Have you checked to make sure there are no engine vacuum leaks? Also, has fuel pressure been checked? I realize the injectors are working but the fuel pressure could be weak, or the regulator could be allowing pressure to be high.

By chance, do you have a live data scan tool? If you do, could you let me know what the short-term fuel trims are? Also, I need you to check the engine coolant temperature sensor signal to confirm it seems to be correct. For example, does it tell the computer the engine is 90 degrees when it is actually at operating temperature?

If you haven't checked for vacuum leaks, here is a link that explains how to do it:

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

Let me know.

Joe

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Saturday, July 30th, 2022 AT 11:12 PM

ABUSTA33

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4 POSTS

Joe,

Thanks, but I do not have a live data scanner. I hooked up a vacuum gauge tester and saw the truck idle at 11 which I read indicates a vacuum leak or possible valve issue. I checked all my hoses and don't see any visible cracks or breaks. I may have a gasket fail on my manifold, but I don't have a smoke tester. Current did a check on codes and it down to a 0303-cylinder three misfire. Thanks for your response.

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Sunday, July 31st, 2022 AT 2:52 PM

JACOBANDNICKOLAS

MECHANIC
109,885 POSTS

Hi,

If it is one specific cylinder, we can do some tests. First, the vacuum reading is lower than expected. Did you try using carb cleaner to locate a leak?

Next, try this. I need you to switch the cylinder 3 coil pack to a different cylinder. While you have it out, check the spark plug condition in cylinder 3.

If the plug looks okay, reinstall the coils in the different places and let's see if the misfire moves to a different cylinder.

Let me know what you find.

Joe

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Sunday, July 31st, 2022 AT 9:45 PM

ABUSTA33

MEMBER
4 POSTS

Joe,

Thank you for the advice but after trying to find a leak I could not. I took it into a shop, and everything looks great with the exception of some carbon build up on my pistons and valves. I was provided pictures and saw that the buildup was not allowing my valves to seat properly and allowing some oil in which starts to foul my plugs. Valve is also an indicator of my vacuum gauge test reading 11 in which I read.

Al

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Friday, August 5th, 2022 AT 4:59 PM

JACOBANDNICKOLAS