I started this job on my truck with a bad MDS solenoid on cylinder 1. I have had to replace them before so i went ahead and replaced all 4. After the install I had misfires on cylinder 1 and 7 coming across ad a random misfire code P0300. I decided to replace the spark plugs as well and it ended up fixing the misfire on 1. I still had a misfire on 7 after replacing the spark plugs and the coil pack so i went a head and replaced the fuel injector as well just incase that was the issue. After i reinstalled every thing and turned the truck back on, I am getting another P0300 fault and a flashing engine light. I am honestly at a loss. I feel every time I "fix" one problem, another rears its ugly head. Any ideas on what to do next?

So far I have:

1. replaced all MDS solenoids and intake manifold gaskets
2. Installed new spark plugs
3. Installed new coil pack and fuel injector on Cylinder 7
4. Cleaned off the other fuel injectors and made sure the holes on the engine were clean.
5. Triple checked all physical and electrical connections

 

What spark plugs?

Flashing check engine lite is telling you the computer is detecting misfires. If you have a scanner that can read them, have a look at the misfire counters. See which cylinder(s) are acting up.)

 

i get a P0300 fault. Initially before replacing the fuel injector it was a P0307. I replaced all of my spark plugs.

 

What plugs did you install?

 

oh lol my bad. Autolite iridium xp plugs. I made sure they were gapped to .45

 

That may be part of the problem...... These trucks are notorious for not particularly caring for the rare-earth fellers. Mystery misfires is only one of the potential problems. Swap 'em out for some standard copper plugs, brand of your choice, see if the problems go away.

 

I went ahead and changed out the plugs with new copper ones. The other plugs seemed to still be in good condition but the ones in cylinder 7 were fouled up a bit. One of the diodes was pretty chewed up and both were blackened. The engine seems to be running a little better but I still have the P-0300 fault.

 

Can you feel the misfires???

 

I know it has been a minute. So i took the truck to a mechanic and had a lot of things looked at. I have good spark, good fuel, and good valve springs. He said what is happening is an intermittent issue with the compression in cylinder 7 and 4(both MDS cylinders). He said that they will sit at good psi when you just turn the truck on. And if you let it sit for about an hour and go back it has bad compression. So he thinks it might be a bad lifter or at worst a bad cam. At this point, If i cant find a fix I'm just going to have to sell it as it. I still cant shake the fact that it might still be that i have 2 bad solenoids that came that way from the store. At the start of this project i had no issues with cylinder 7 or 4. Only 1 was misfiring and at one point it was just 7 that was misfiring and now somehow 4 has also become an issue. so part of me thinks that the solenoids i bought were actually bad and that is the real issue not lifter or a cam.

 

I posted an update but forgot to reply to your comment