Misfire problem
 

Hey anyone have a problem with multiple misfires. I have an 01 montero that started with a cylinder 5 misfire. I tore it apart put new plugs, wires, fuel injectors, coils, crank sensor and ignition control module. And every time I tear it apart I get a different misfire code. I have had a cyl 5, cyl 2, cyl 6 and a random misfire. I’m at a loss now on what to do next. Any help would be appreciated

What tool/method were you using to "observe" the misfires? Scanner... probe...

Just a scan tool that reads the codes

P0305 now P0304
 

Not what you're describing, because I'm not there, yet, and don't want to just shotgun blast a bunch of parts at it, hoping to hit the fix.

But my 04 3.5L started posting a P0305 a few weeks ago, only after a while of driving. I swapped coils and it stayed in cylinder 5. So, I swapped plugs from 5 and 1 and whalah; the P0305 went away, but now is a P0304. So, that makes no sense... because the 1 and 5 were swapped, not 4. So, on the strange chance that, since 1 and 4 share a coil, I got a new spark plug and put it in cylinder 1. But, no... the code remains now in 4. As you know, the PIA of this car is getting to any of the plugs, but anyone have an idea? Thanks.

The following is a quote from someone else. Not referencing a Montero. I scraped it and saved to text file to read later. I didn't read it until today. :)
I'm thinking this includes several questions that may be useful to you. I hope so anyway.
Also, with regard to the parts you've replaced how many, if any, are after market? I've been burnt several times. Sadly it adds more variables as you diagnose. :(

"First, what year and model van do you have and how many miles on it?

Second, when exactly did the rough idle just start? Was it after the timing belt/valve adjustment/injector maintenance or just after the transmission repair, and has it been that way since you picked it up?

Third, what are the DTC's that are coming up? When the check engine light comes on that indicates DTC's stored in the computer. I'd assume a P0300 which is a random misfire but is there anything else?

Fourth, I'd want to look at the fuel trims on a scan tool. Is it running too rich or too lean? Is it only misfiring at idle and not at higher RPM's? If so, and if fuel trims indicate it's running lean it could just be a vacuum leak.

When it's running rough I'd want to do a cylinder drop test where you unplug one plug wire or coil at a time and see if the idle drops. That is the way to determine, exactly, which cylinder(s) is/are misfiring. The misfire counters aren't always accurate in telling you which cylinder is misfiring. I'd also want to do a compression check."

Codye........A friend's '99 Monty was having the same issue. Turns out that there exists a little "Ignition Transistor" that can fail and cause these mis-fires, and then the engine will not start if the transistor "gives up the ghost".

I have posted detailed pics of this part in a recent thread called:

1999 Montero Ignition Control Module or Capacitor?

Here is the link:

https://mitsubishiforum.com/forum/mi...pacitor-57367/

If you read this, it may help you solve your problem.
Let me know if it helps, and if you have this little transistor on your 2001.