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Ask Doug Your Own Question
Doug, ASE Certified Technician
Category: Mitsubishi
Satisfied Customers: 8621
Experience:  Mitsubishi employed and Factory trained ASE certified technician
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Sorry for not getting back sooner but I had a personal issue

Customer Question

Hey Chris, sorry for not getting back sooner but I had a personal issue and now I'm back trying to finish what we started.
Just to get you up to date, I changed the transistor on this 02 Montero Sport and it starts but it's running like it restricted with a stopped up catalytic converter so I took it off and still the same, I'm not getting any codes on my scanner but the battery and brake like came on in the cluster, don't know if that's a sign of a bad ground or something else. I took it for a spin and it kicked in sometime like it was just clearing out bad gas but that was short lived. I'm puzzled and wondering if one of the ign coils could be malfunctioning or do they just go out all together. Any help or suggestion would be appreciated.
Submitted: 1 year ago.
Category: Mitsubishi
Expert:  Chris (aka- Moose) replied 1 year ago.

Sorry I can not help on this post. Last time I assisted i was never compensated. Opting out now.

Customer: replied 1 year ago.
What do you mean you weren't compensated, was it something I didn't do?
Expert:  Doug replied 1 year ago.


The battery and brake lights could well be related to the poor running... these coming on is indicating that the system voltage is too low. This is usually due to a failing or aftermarket alternator on this model.
I would start by supplying auxiliary power (charger etc) to the battery while running and see if it clears any... if it does, then address the charging problem.
If it does not, then you will need to get back to basics and check the individual spark on each coil output to make sure all six are operating... obviously if not then you have a strong direction to head (isolating coils, checking belt timing for computer controlled coil shut down), and if you do have solid spark on all six outputs then I would move forward with compression testing the engine, checking the individual injector flows in case you have one injector that is sticking etc.

Customer: replied 1 year ago.
Thanks, I'll try hookup up the battery charger first to see if that turns those lights off. I notice when I start Erving engine it doesn't sound like it's running bad it just doesn't reflect the rpm like it should, it sounds like it's reving high but the tach gauge shows between 1&2 but it is affected when I put it in drive and it will move slowly.
Customer: replied 1 year ago.
Supposed to be revving engine in above post, sorry
Expert:  Doug replied 1 year ago.

Yeah check that first... with the symptoms you have being pretty broad it may be something that is better seen in person for best interpretation.

Customer: replied 1 year ago.
Can the coils function poorly but still function? I put a cheap test light pencil on the plug wires coming out of coils and the one on far right (drivers side, cylinders 3&6.
Customer: replied 1 year ago.
Was very strong but the other 2 were weak and sometimes would pick up a spark, but as I stated its not having any codes ��
Expert:  Doug replied 1 year ago.

Yes, it is possible to have the coils be weak, that is not unusual particularly with certain aftermarket coils that are of poor quality.
I would try rotating the coils around and see if the strong one moves with the coil or if it stays on the same position (swap another coil in that position and it becomes strong for example).

Customer: replied 1 year ago.
Sorry again about previous post wording, I was typing to fast, the other 2 would not pick up a spark sometime.
I put a battery charger on and it did increase the idling rpm but still not running like normal and the lights stayed on except for when I accelerated, but while holding a steady rpm at about 2 the lights would come back on.
Customer: replied 1 year ago.
Okay, can I do that? The 2 on left & center are the same with black plug in and the string one on right has a white plug and different mounting holes.
Customer: replied 1 year ago.
Supposed to be strong one on right ��
Expert:  Doug replied 1 year ago.

If you are dropping spark entirely on those two coils and the coils themselves are not the issue (same positions drop when rotating the coils) your only possible causes would be PCM, ignition module, wiring, or belt timing. Since it comes and goes it seems, belt timing is out.
The coils can be swapped, you just can't bolt one of them down in the wrong position, still works fortesting though.

Customer: replied 1 year ago.
Ok ill try that and see what happens, I changed transitor or ignition/igniter module and the truck did start whereas before it was totally dead
Expert:  Doug replied 1 year ago.

Did you use a new genuine igniter? This is a common failure point on these so used ones are not a safe bet, and aftermarket electronics in general on Mitsubishis are a disaster most of the time.
The fact that it went from nothing to running makes it sound like you were right the first time, you just may have gotten a bad part.

Customer: replied 1 year ago.
It was a new igniter, got it from Oriellys auto parts so it wasn't from Mitsubishi.
I swapped all coils and as you thought they all performed good when I hooked them to the 3-6 cylinders so I'm guessing it's the ECM? Can it function partially or does it go out all together? I'm still puzzled that I'm not getting any codes. Is there a way I can look for something with my scanner/diagnostic tool to lead me in the right direction?
Expert:  Doug replied 1 year ago.

I would be trying a genuine Mitsubishi igniter first. Aftermarket ones rarely work even when brand new. Working for a dealer we see these towed in from other shops with aftermarket igniters and sensors on them all the time where all they needed was a "good" part and not just a "new" part. Aftermarket electronics and Mitsubishis do not mix... at all.