Hey guy I have a 02 Montero limited 155k 2 weeks ago I get cel p300 random/misfire. Truck was idling rough with rpms dropping to 200 and having trouble accelerating at times going past 20 mph. I changed the spark plugs and cel turned off and truck ran smooth for a few days then cel came back on with same code. Now it is doing the exact same thing. I'll drive it for about 10 min then rpms drop making it hard to accelerate and giving me a rough idle when at a light or parked. I checked the spark cables and when it's idling rough I got no spark from the ignition coil closest to driver side cables 3/6. But when it's idling fine I do get sparks from 3/6. I went and bout the ignition coil and nothing changed same problem so I took off the new and returned it. After following the plugs to the ignition module I noticed that when I jiggle the main plug that gives power to the ignition coils on the module the truck changes from rough idle to normal. At first I thought it was the plug that connects into the ignition module because I noticed it was cracked on the lip where it connects and thought it wasn't making good contact so I replaced it with another one from junk yard. After doing this its still going on. If I jiggle the plug on the module truck is fine then it's not. Not sure if it's the actual module itself don't want to spend 150$ on it and it not be the problem.
TIA I hope I don't confuse anyone

 

Follow the repair manual steps to diagnose and correct. Electric issues can be a pain in the butt to diagnose, as it might be as simple as a fuse/relay or as complicated as a frayed wire somewhere. It might be time consuming, but it is your time, and you are not spending money buying parts that might or might not be failing.

 

You can buy and download a repair manual for your truck from many EBay vendors for approx. $10.00, well worth the money.

 

Did you ever find the problem with your truck?