Misfire Help
#1
05-22-2019, 08:15 PM
Misfire Help
Hey everyone, long time no see,
A few months ago, my engine misfired on a few cylinders. I had 90k miles on the plugs, so i went ahead and replaced all 8 plugs with Motocraft plugs, and Autozone Duralast coils (I know, but hear me out.)
The engine ran great, but shortly after, it ejected the #3 spark plug while I was driving home from work. The threads were destroyed, so I used a Timesert kit to repair the head.
After the repair, the truck ran fine, but had a very intermittent miss only when in overdrive between 40-45 mph. The SES light did not trigger for several hundred miles. The miss got progressively worse over that time period until now, the truck idles rough, and misfires across the rev range and under acceleration. With the SES light now on, the code was P0300 and P0303.
I feared the worst and thought I may have damaged an exhaust valve performing the Timesert. I still doubt this is the case because I followed the instructions to the tee, and used the method listed to check that the cylinder was on the compression stroke by feeling for air escaping through the plug well.
Additionally, I performed a compression test on the engine bank and all 4 are healthy: 1 (180), 2 (175), 3 (175), 4 (180).
After inspecting the plugs, #3 is squeaky clean. I can post pictures, if needed. Is this an indication of an injector or ignition problem? The easiest thing for me to suspect was the Autozone coils, so I exchanged #3 for another one, and the miss persists.
The last thing I could think of is damaged wiring from the plug blowout, but I do not know how to check/what values to read. Any help?
2003
5.4L
4x4
263k
A few months ago, my engine misfired on a few cylinders. I had 90k miles on the plugs, so i went ahead and replaced all 8 plugs with Motocraft plugs, and Autozone Duralast coils (I know, but hear me out.)
The engine ran great, but shortly after, it ejected the #3 spark plug while I was driving home from work. The threads were destroyed, so I used a Timesert kit to repair the head.
After the repair, the truck ran fine, but had a very intermittent miss only when in overdrive between 40-45 mph. The SES light did not trigger for several hundred miles. The miss got progressively worse over that time period until now, the truck idles rough, and misfires across the rev range and under acceleration. With the SES light now on, the code was P0300 and P0303.
I feared the worst and thought I may have damaged an exhaust valve performing the Timesert. I still doubt this is the case because I followed the instructions to the tee, and used the method listed to check that the cylinder was on the compression stroke by feeling for air escaping through the plug well.
Additionally, I performed a compression test on the engine bank and all 4 are healthy: 1 (180), 2 (175), 3 (175), 4 (180).
After inspecting the plugs, #3 is squeaky clean. I can post pictures, if needed. Is this an indication of an injector or ignition problem? The easiest thing for me to suspect was the Autozone coils, so I exchanged #3 for another one, and the miss persists.
The last thing I could think of is damaged wiring from the plug blowout, but I do not know how to check/what values to read. Any help?
2003
5.4L
4x4
263k
#2
05-22-2019, 09:55 PM
#4
05-26-2019, 11:02 AM
