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2000 Mitsubishi Montero Sport 3.6L 4WD won't run for more than a few minutes - ??catalytic converter failure??
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jtmill02
New User
Sep 13, 2011, 6:28 PM
Post #1 of 6
(4764 views)
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2000 Mitsubishi Montero Sport 3.6L 4WD won't run for more than a few minutes - ??catalytic converter failure??
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upon leaving work on sunday night, got to my 2000 Mitsu Montero Sport 3.6L 4WD and realized i had left my lights on (recurrent bad habit) and the battery was DEAD. had a friend right there who was happy to give a jumpstart. in a hurry to get home, i carelessly crossed the cables. after realizing the problem, i successfully started the car but it quickly died 30 seconds after the cables were disconnected. figured i had fried the alternator and got the car towed to my dealer.
here's where it gets funny. dealer checks it out yesterday and confirmed the alternator was shot as well as the battery. replaced both as well as a couple of fuses that were also blown. but when they started the car and let it idle, after several minutes the engine began to sputter and subsequently stopped running. after sitting for a while, it would start and run fine, but then after a couple more minutes stop. based on the way it was running, the tech felt like it was a problem with blocked exhaust. he removed the oxygen sensor in front of the catalytic converter, which supposedly allowed air to escape and the engine ran fine. replacing the sensor almost immediately killed the engine. this led him to believe the catalytic converter was bad, and that as it got hot it was clogging(swelling?) up, obstructing the exhaust.
some of this was communicated to me over the phone, and my initial impression was that it was just running like normal and somebody was just overly sensitive to some rattle or something. of note, it had been running very well before all this. when i got to the dealer, i pulled the car around from where they had parked it up to the service desk to settle up - it ran great for that brief (~30 second) drive. they explained the above to me and recommended that i leave it with them to get their exhaust guys to replace the part. i still didn't quite understand and decided to take my chances.
everything seemed great for about three or four minutes. then it happened. while idling in traffic just in front of the dealer, the engine stalled and died within 5 seconds. i was able to get it off the road and sat for a couple of minutes. it started back up and i drove in the shoulder for about another 50 yards before it died again. after a couple more minutes, i started it back up.
here's where it got funny again. when i started it for the second time, i decided to floor the accelerator to see what would happen. interestingly enough, by doing this, it would sputter but not die. on the trip back through the auto mall (~1/2 mile) it didn't die again, but would sputter for 20 seconds, creeping along at a very low speed, then surprisingly get full power again for about 10 seconds before starting to sputter again. this pattern went on until i made it back to the dealer.
so as of right now, they are confident in the problem being the catalytic converter but without an explanation of why it failed all of a sudden. it is going to an exhaust shop tomorrow where they will run their own diagnostics before possibly replacing it for around $600.
my concerns are:
- my gut tells me that it's not the catalytic converter, rather something electrical. electrical problems are clearly explainable, and the car was running great prior to my bonehead error. i'm afraid of dropping $600 unnecessarily and then starting all over to find the real problem.
- why would the converter fail?? my understanding is that the converters don't really fail on their own, they have to be fouled by fuel rich exhaust burning hot or by some contaminant. my first thought was that if the electrical were shot, possibly there were some timing or sparking problems that led to fuel rich exhaust doing thermal damage to the catalytic converter. one of the guys gave some BS postulation about the fuel formulation used here in KY and that they have been seeing a ton of failed converters - this might explain a chronic failure, but clearly something has happened since sunday.
- if the catalytic converter is bad due to an unexplainable cause which may or may not still be present, what's to keep if from failing again?
- does a failed catalytic converter actually behave this way? i would think you would have problems as soon as the car is started. the explanation that the converter was getting hot and clogging once the engine had been running doesn't make a lot of sense to me, but i don't really have any knowledge base in this area.
of note, the computer had no error codes at any point during this fiasco. also, i bought the car from this dealer and have dealt with them for 11 years. same service manager, and thus far have never had any problems or felt gouged by them.
any input would be greatly appreciated.
thanks in advance,
jason
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Hammer Time
Ultimate Carjunky
/ Moderator
Sep 13, 2011, 6:47 PM
Post #2 of 6
(4757 views)
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Re: 2000 Mitsubishi Montero Sport 3.6L 4WD won't run for more than a few minutes - ??catalytic converter failure??
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My gut is agreeing with your gut. It's not acting like a plugged Cat and appears electrical but the only way you are going to find out is by doing some testing during that period when it won't start. You need to test for spark, injector pulse and fuel pressure to isolate the cause.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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Discretesignals
Ultimate Carjunky
/ Moderator
Sep 13, 2011, 6:56 PM
Post #3 of 6
(4753 views)
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Re: 2000 Mitsubishi Montero Sport 3.6L 4WD won't run for more than a few minutes - ??catalytic converter failure??
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Usually if a catalyst is clogged to the point the engine won't run, it won't all the sudden unclog itself. It would be a first for me to hear of a catalyst being clogged only when warmed up.
To verify a restricted exhaust the best way is to screw a back pressure gauge in the O2 sensor hole before the cat. When the engine is running the pressure shouldn't be anymore than 3 psi at 2000 rpm. It might have been a coincidence the engine ran with the O2 sensor out. Did he unplug the O2 sensor connector to see if the engine ran better with the O2 sensor screwed into the exhaust?
Crossed battery connections might of nailed your engine controller or any other solid state device in the electrical system. The problem really needs to be diagnosed again to see what is actually missing when the engine doesn't start after it has stalled.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
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jtmill02
New User
Sep 15, 2011, 2:21 PM
Post #6 of 6
(4709 views)
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Re: 2000 Mitsubishi Montero Sport 3.6L 4WD won't run for more than a few minutes - ??catalytic converter failure??
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UPDATE - Car went to exhaust shop yesterday morning. They quickly ruled out the catalytic converter as the problem - all the exhaust testing was fine. Back to the dealer, where they apparently spent a good part of the day trying to figure out the problem. They finally decided the problem is a fried fuel pump control module. This makes more sense to me given the mechanism of damage, so I was satisfied with the explanation, even though I don't have any idea what a bad fuel pump control module would act like. The part will take a couple days to come in but will cost half of what replacing the cat would.
Thanks for everyone's input. I'll update when the part gets replaced.
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