I could not find NPR recommendations on how to breakin their piston rings.

Hastings is a well known OEM supplier of rings so I followed their recommendations which are to hold engine at an rpm corresponding to about 25mph (I guessed and took this to be 2000 rpm) until coolant reaches normal operating temperature (took about 10 minutes for thermostat to open based on feel of upper hose all the while running the heater at max hot ) followed by driving vehicle and making at least 10 full throttle blasts from 30 to 50 mph. No further breakin required. Avoid sustained high speed (constant speed) during the first 100 miles.

I can't believe how well it runs. Runs like a new car. Been dead 2 years. Currently getting its safety inspection and will then be put back into the family fleet.

I plan to change the oil at 500 miles. Will try to cut open the filter to see what if anything is in there. Also have the magnetic oil drain plug.

Only work remaining is to put the under pans back on and the wheel well rubber access panels. I intentionally left these off to be able to check for leaks.

 

Congratulations!!! It's been awesome to follow your thread. You've done amazing job documenting the process. If I ever have to do an engine rebuild on my Monty, I know where I'll be able to find lots of helpful info.

 

Thanks Hunter! It has been an adventure to say the least. It has been a long time since I rebuilt an engine (Plymouth 440 back in 1979), and I have to say I am much smarter now than I was then. The internet is truly a blessing in this regard. I have learned a lot from the net and my thread is my way of contributing to others and hope others find it useful with info in one place.

Monty passed safety inspection yesterday, but the shop that did the safety inspection said the alternator and battery needed replacement. I replaced the battery and will check the alternator.

The engine had 173,875 miles on it at time of bearing failure. I hope to put many more miles on it now.

 

After return to service, I have had to replace the battery and the alternator. Alternator details here starting on Post 10 https://mitsubishiforum.com/forum/mi...e-light-47742/

The Service Engine Light (SEL) had come on while I was driving to Autozone to replace the battery at Autozone. The Codes were P0403 EGR Control Solenoid Circuit Malfunction and P0306 Cylinder 6 Misfire Detected. Engine was running fine with only a very slight rough idle.

Disconnected the battery and replaced the alternator and the EGR Control Solenoid MR281265 which I bought for $44.72 at a dealer near me. With the Codes clear, proceeded to drive for 25 miles with no issues.

Next morning the SEL cam back on. Rough idle with a miss on one of the cylinders only at idle, revs and runs smooth at off idle. Bought a Harbor Freight code reader 60693 and it shows P0306 Cylinder 6 Misfire Detected and a pending code P0431 Warm Up Catalyst Efficiency Below Threshold Bank 2.

During the engine rebuild, I installed all new plugs and wires, so I am thinking the Cylinder 6 misfire is a vacuum leak from an injector o-ring or the injector itself. For the interim, I put Chevron Injector Cleaner with Techron into the gas tank and will run it out in hopes that it is an injector issue that will clean up. The vehicle had sat for 2 years with 1/2 tank of fuel in it prior to the engine rebuild. When I got the vehicle back on the road, I filled it with 93 octane Shell and have run about 1/2 tank at this point.

Cylinder 6 is on the left (driver's) bank. I think Bank 2 is also the left bank (can someone confirm?). Do you think the P0306 and the pending P0431 are related? I have all new Denso O2 sensors.

 

You are correct - Cylinder 6 is driver side by the firewall. I would not rule out the possibility of P0431 code being related to the misfire on #6, since both are on Bank 2. You'll have to figure out the misfire code and see if the P0431 will show up again after the misfire got addressed.
The problem is figuring out what causes your misfire. I had a misfire on #3 cylinder happen, and it turned out to be due to spark plug boot getting saturated with oil from the spark plug well (old hardened seals). That caused the boot to expand and literally pop-off the plug. In your case you have new plugs, wires and seals. So that rules out this possibility. I seriously doubt that a vacuum leak at injector could possibly be massive enough to cause a misfire. Personally, I'd be focusing on the wiring and connectors at the coils. You can also check to see if the plug wire on #6 cylinder is sitting a little higher relative to the valve cover than on other cylinders. Theoretically it could be not be seated all the way on the plug and causing an intermittent issue.

 

Hunter - thanks for help. Good insight!

I used an inductance probe just now on the ignition wires (type of probe electricians use for presence/absence of voltage). I have voltage on all but Cylinder 6 plug wire. The coil is common to Cylinders 3&6. I need to find my timing light but used the probe instead.

Does this engine use a "wasted spark" scheme (i.e. plugs 3&6 fire same time but one cylinder the spark is at a useless point in the cycle)? For example, can I swap the plug wires between 3&6 to confirm the plug wire and plug for Cylinder 6 are good and move the problem to Cylinder 3? This would mean the coil pack is bad. Do coil packs fail losing one side only? I did just now clean the connectors to coil 3/6. Oddly, this coil has a white female connector while the other 2 are black.

I'm able to look under the plenum and the boot for Cylinder 6 plug looks to be fully seated.

 

Yes, this is a "waste spark" system with both cylinders having the spark occurring at the same time. I do not believe these coil packs can have only one side malfunction - it is a single coil that produces two sparks at once. If your coil pack was bad, you would have misfire (no spark) on both #3 and #6 cylinders at the same time. Since you are not having this issue, it is either plug wire, spark plug or an injector issue. Do you think it is possible that the injector on #6 is malfunctioning? You have a signal going to it, but it can be stuck open or stuck closed. If its stuck open, it would cause the rich condition with a bunch of unburnt fuel going down into the bank 2 cat converter - hence the P0431 code.

It sucks, but I'm afraid you are going to have to pull the plenum again to check this. You can try to rule out spark plug by swapping #6 plug with another cylinder. This way you can see if misfire moves to a different cylinder. Not sure if any other wires would reach to #6 cylinder, but you can swap the plug with one cylinder and swap similar length wires with another cylinder to rule out both plug and wire at the same time.

 

Did a little more investigation:

With engine off, I disconnected the #6 plug wire from the coil. Installed an old plug wire from the rebuild to the coil and used an old plug that I grounded. Started the engine and the test plug had spark, not brilliant blue, but orange/white. Granted the plug had who knows how many miles on it. Turned off the engine.

Removed the test wire and plug. Moved the #6 plug wire to the #3 coil position and the #3 plug wire to the #6 coil position. Started the engine. Inductance probe shows voltage on the #6 wire and sporadic voltage on the #3 wire. Cleared the trouble code and will now drive it to see if I get a Cylinder 3 misfire.

I should have used the test plug and wire on the #3 coil position to see if it produced better spark than the #6 position.

This thread talks to it being extremely rare for one side of a dual coil pack to fail but does not rule it out Mitsubishi Montero Sport: got a check engine code error misfiring

Unrelated, but my brother's Saturn had one side of a dual coil pack fail. That engine also uses the wasted spark scheme and he swapped wires to shift the problem to the other cylinder to confirm the coil failed.

Looking on line, these engines oddly use 2 different coil packs:
MD314582 (~$63) Type 2 is for Cylinders 3 & 6 and has the white female connector
MD314583 (~$167) Type 1 for Cylinders 1, 2, 4, & 5 and has black connector

From what I can find, Diamond is the OEM for these coils. The Type 2 is FC0020 and the Type 1 is FC0021.

I will do some more testing and driving, but I am thinking the Coil for 3/6 is bad.

Anyone have any luck with aftermarket coils, or back to the dealer for this?

 

Drove the vehicle for about 20 miles with the #3 & #6 plug wires flipped at the coil, no code set. Engine has no miss at off idle conditions that I can sense. Granted I started the vehicle from cold, and promptly drove away (see below, I'm now thinking improper drive cycle).

Disconnected battery (cleared codes) while I replaced the #3/#6 coil pack with a new one from Napa and installed plug wires in proper orientation. Still have a miss at idle, drove 20 miles, no code. Next morning, started vehicle, let it idle and come up to temperature before driving. Upon acceleration out of the driveway, promptly set P0306 again with P0431 pending. Screen shots of the Freeze Frame data are attached. Any insight from the Freeze Frame data?

The manual lists conditions necessary to set a P030x (x is cylinder number). One of the key items I noticed is that the "Misfire has occurred more frequently than allowed during the last 200 revolutions when the catalyst temperature is higher than 1742F". Since the miss does not seem to appear at off idle, I'm thinking that me promptly driving a vehicle from a cold start does not set the code as the cat is cold and I'm off idle driving when no miss seems to occur.

The inductance probe shows sporadic spark on one leg of the new coil while at idle which seems to go away as the rpm increases. Same behavior for the removed original coil. My probe is a cheapie so I take this with a grain of salt but it is repeatable - no other plug wires show issue and it follows the flipped wire from the 3/6 position. I need to get smarter on what is driving the coils. I will check the ICM (Ignition Control Module).

My plan of attack for the weekend is:

1. Swap #3/#6 plug wires on new coil and clear codes. Do a cold start with prolonged idle until up to temperature before test drive. Hopefully this will change the P0306 to P0303 proving ignition side problem.

2. With engine running at idle, try to spray ether (spay start fluid) in the vicinity of the #6 intake ports. If a vacuum leak, then RPM's should increase.

3. Using scan tool, record Bank 1 & 2 short term/long term fuel trims and O2 data at both idle and off idle conditions. From what I understand, this should be able to detect a vacuum leak condition although not show where it is located (vacuum leak at idle means O2 sensor demands more fuel to burn excess oxygen, vacuum leak at off idle is much smaller portion of total air consumed so O2 sensor compensates with less excess fuel)

4. With engine off, disconnect the fuel injection harness connector at intermediate connector B-44 (on top of passenger valve cover) and Ohm out the pins. This will get the combined circuit effect of the harness with injector without having to pull the plenum. If there is an issue, then I will have to pull the plenum to determine if the circuit issue is with the harness, the injector, or both. Sure do wish I had tested the injectors' resistance while they were removed.

This is an old P0306 post but if you wade thru it the OP finally traced his issue to a bad injector while another had a vacuum leak and yet another had an ICM failurehttps://mitsubishiforum.com/forum/mi...der-6-a-16880/

This link also provides details for testing the ICM which the OP determined was the cause of his P030x. I shamelessly stole the testing detail and will also check this. Need help: #1 cylinder misfire problem | Monterosportonline.net Forum

 

I think your plan of attack is good. Looking at the Freeze Frame data, I would rule out misfire due to lack of fuel and rule out a vacuum leak. Your fuel trims are looking good with no indication of vacuum (fuel trims would be 20+% if you had a severe vacuum leak). Most likely you are dealing with a spark issue. Try to replace the #6 spark plug, or better yet - move it to a different position (perhaps a #4). This way you'll see if your code will jump from #6 to #4 - then you are have a faulty spark plug and exclude (or not) the faulty coil.