1999 Montero ignition module gets hot

Paul Technician Arizona Posted   Latest  
Unsolved
Driveability
1999 Mitsubishi Montero Sport Limited 3.5L (R 6G74) 4-spd (AW30-40LE)

Hi all, I'm new, so bear with me. I and another tech have been fighting a problem with this Montero. It started with a timing belt replacement, we found a bad reluctor wheel and damaged crank sensor. All replaced as well a tune-up plugs coils and such. Now the engine starts and runs great for about 40 seconds then starts to miss and the module gets crazy hot. Replaced module ( aftermarket ) and same problem. Power and grounds ok, the waveform is ok until the misfire, replaced with another module with the same effect. No codes, Of course, it ran fine before repair, this was just a maintenance issue although why no codes with damaged reluctor? Any ideas out there? Thanks, Paul

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Stephen Technician
Tennessee
Stephen
 

The too hot module indicates that it is on for too long or on too often or both or has too high of current draw on it(coil). A current ramp and voltage trace of the module B+ would be a good test. The CKP is directly involved in s… production so, I wonder about what it is putting out. I wonder how it ran fine before with a bad reluctor and damaged CKP but doesn’t after new is installed?

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Agree
Joe Owner
California
Joe
 

Try running a ground jumper from the module to the negative battery post/clamp. Do you have the old plug coils? If so try putting them back in. Old Guys KISS method! if it doesn't work check power. If it acts stupid check the ground.

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Tom Owner/Technician
Tennessee
Tom
 

I'd put the old coils back in and see what happens. They could be drawing more current than OE. Tom

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Scott Manager
California
Scott
 

Hi Paul, One idea that comes to mind is to take a look at the ECM's interpreted system voltage and make sure it's correct. If it's seeing something lower than actual this can lead to increased saturation time (circuit overheating). Although the attached image from a GM calibration, it is a modifier table I would assume that other engineering teams have adopted similar strategies in order to…

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Thanks
James Technician
California
James
 

Is this with the module mounted, or just plugged in ? The module has to be mounted on the bracket\heatsink so that it does not get hot. It also has to have a fresh layer of white grease under it to transfer heat away.

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Paul Technician
Arizona
Paul
 

I agree that there should be a heat sink but there wasn't one on this unit, so I'm confused, why would it need one when it didn't come with one and the engine ran ok without it?

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Eric Owner/Technician
Wisconsin
Eric
 

The mounting bracket is the heat sink. Most good replacement modules come with the bracket, I've seen modules just zip tied to the original bracket/module and those modules overheat. As far as your overheat problem, as long as the module is bolted to the bracket (did it come with the new module) you should be okay. I would be checking power and ground circuits as well as coil dwell (on) time to…

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Obie Technician
Washington
Obie
 

You stated the waveform is okay until the misfire. Can you post a picture of the waveform before and during the misfire? Someone here may have a known good to compare it with.

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Olle Instructor
Minnesota
Olle
 

Are you absolutely sure about the cam timing? Some of these critters (Honda, Mitsubishi, etc) will have too long of a coil on time if the engine timing is off.

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