P0300 & p0301

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#11

01-15-2023, 02:51 PM

panthersnc

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Quote:

Originally Posted by LesMyer

Some softwares can report misfires, but on the wrong cylinder. Seems a couple of cylinders can get switched. Pull #1 plug wire from the cap and make sure it doesn't start reporting misfire on a different cylinder. Car Diagnostic Pro has alternate PIDs for the two troublesome cylinders. Looks like you're using Dash Command - I don't know if it has this issue or not. It's easy to test by pulling plug wires.

Quote:

Originally Posted by GeorgeLG

In addition to the other things we are looking at please follow Les' direction and pull some plug wires while running to confirm proper misfire cylinder reporting before we get too carried away. The usual starting point is to get CMPR within sped to help with this but you already have that taken care of,

George

Driver Side Spark

Passenger Side Spark

#12

01-15-2023, 06:14 PM

panthersnc

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Quote:

Originally Posted by GeorgeLG

Can you feel the miss?
Have you done a fuel pressure/leak down test?
Did you do a full compression test or just cylinder 1?
What does the #1 plug look like?
Has there been any carbon traces under the distr cap?
Try misting the ignition system in the dark at idle and look for spark
Let’s look at your fuel trims at idle and 2500 in park

George

3. Compression Test

#13

01-16-2023, 12:02 AM

GeorgeLG

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Location: Florida

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There is something going on with that #1 cylinder based on compression (148). Its not catastrophic but its outside the 10% uniformity guideline and may be responsible for the cylinder misfire. Did your squirt some oil in that cylinder and repeat the test to see of the compression came up to the other cylinder numbers (165-178)? You can also do a drop cylinder test by grounding the spark and comparing the rpm loss to a couple of other cylinders. Any recent engine work?

As you said the plugs all look about the same so nothing dramatic there

Nothing dramatic in fuel trims except that they go from negative at idle to positive at 2500. Thats the opposite of a vacuum leak and may indicate a mild fuel delivery or sensor issue. Lets see what the fuel pressure test says.

George

#14

03-12-2023, 05:52 PM

panthersnc

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Sorry about the late reply. The blazer overheated one night and I started getting antifreeze into my oil. I did do fuel testing and found I was only getting around 30-40psi before the filter and it was weird started raising a little. Been a few weeks though but I believe the leak was only from my intake manifold gask alert but I ripped the heads off to make sure but it’s back running so I can find th other issue lol

#15

03-12-2023, 07:17 PM

GeorgeLG

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Location: Florida

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The lower intake manifold (LIM) gaskets are a righta of passage for blazer owners. If you used the high end Fel Pro set you should be good for the duration.

George