My confusing 3.0

[K Thompson]

Afternoon Guys:
I have a 2003 3.0l xlt. New new wires, plugs, coil pack, and cam syncro in the last 20K miles. While driving, I got a hard intermittent miss under load at low rpm and has become worse. My code reader gives a P0301 code. I figured must be a bad injector. Replaced with new SMP brand still P0301. Switched out wires and coil pack still P0301. Replaced the plug and no more P0301. It is now P0302. I don't know what to make of this and would appreciate some advice from you guys.

Thank You
Keith

 

[rusty ol ranger]

Did you swap plugs?

Or actually replace it?

Try changing plug #2

 

[RonD]

When there is a misfire remove all 6 spark plugs first, check the tips
Then do a compression test on each cylinder and write down results
You are looking for a greater than 10% difference

So if 5 are 155-165psi and one is 140 or less then there is a problem in that cylinder
Or if 4 are 155-165psi and two are less than 140 then there is a problem with 2 of them

3.0ls, like most engines, burn exhaust valves, most common issue for misfires when its not broken or failed spark plug

 

[K Thompson]

Did you swap plugs?

Or actually replace it?

Try changing plug #2

I put a new plug in #1 thats when the code changes to P0302

When there is a misfire remove all 6 spark plugs first, check the tips
Then do a compression test on each cylinder and write down results
You are looking for a greater than 10% difference

So if 5 are 155-165psi and one is 140 or less then there is a problem in that cylinder
Or if 4 are 155-165psi and two are less than 140 then there is a problem with 2 of them

3.0ls, like most engines, burn exhaust valves, most common issue for misfires when its not broken or failed spark plug

I will get a compression tester tomorrow and check it out. Thanks.

 

[RonD]

Have all 6 spark plug removed when doing a compression test, so you can get accurate results

With 0psi compression on 5 cylinders then you get a true reading on the one being tested
If you just remove the 1 spark plug to test the one cylinder then cranking speed varies unless ALL 5 cylinders are exactly the same compression, which of course they are not
Compression is a temporary thing, can't get an airtight seal with metal on metal rings and valves, lol, so cranking speed matters, but only when comparing the results
Also if there is a blown head gasket between two adjacent cylinders you can miss that entirely

 

[K Thompson]

Solved!!!!!!!!!!!!

Bad coil pack. SMP less than 2 years old. I am going forward with Motorcraft only. Lesson learned.

Thanks for your responses guys!!!