Question about Mitsubishi Montero Sport

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Truck starts but dies after 5 sec or so

Truck starts right up but then dies after about 5 sec or so. any help would be awesome.

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Check the fuel pressure and compression and O2 sensors

Posted on Apr 13, 2014

  • 38 more comments 
  • Casey Jones
    Casey Jones Apr 13, 2014

    after is sits for a while, i can start it and it will fire right up and run for about 15 or 20 seconds like theres no problem but then all of a sudden just die. it fires right back up and only runs for about 5 seconds before dieing.

  • Graveyard Tech Apr 14, 2014

    Have all codes checked, but remember it all starts with the O2 sensors

  • Graveyard Tech Apr 14, 2014

    Off the top I would say the catalytic converter is clogged

  • Casey Jones
    Casey Jones Apr 14, 2014

    it doesnt run long enough for the check engine light to come on and ive checked for codes and it will not run long enough to scan. i'll check the catalytic converter.. thanks

  • Graveyard Tech Apr 15, 2014

    Do you have the 3.5 V6? What year? How many miles?

  • Graveyard Tech Apr 15, 2014

    Be prepared for new parts could be defective!

  • Graveyard Tech Apr 15, 2014

    If you could do this: Autozone has a scanner, on sale, for 99.95 untill May 5th.

  • Graveyard Tech Apr 15, 2014

    This scanner has " live data"; while it runs. Plug it in, fire up the engine, pushe the down arrow as you watch the voltage reading for that 5 seconds , check if a voltage is NOT moving.

  • Graveyard Tech Apr 15, 2014

    If the voltage moves slow that is a good replacement item!

  • Graveyard Tech Apr 15, 2014

    I know 100 bucks is high , but this scanner you could use it on anything!!! Anyone who has a darned fuel injection system should have one of these!

  • Casey Jones
    Casey Jones Apr 15, 2014

    first off its a 98 3.0 with around 188k miles. i have a code reader but the check engine light isnt on so its not reading any codes. i could go and start it right up and it would start up and seem like its running perfect for like 15 to 20 seconds and then its like you turned the key off and dies. start it right back up with no issues but then only runs for 5 to 10 if that. I'll look into getting the other scanner i looked it up and ive got the model below that one. thanks for the tip and im always looking for a deal that will help make this truck maintanance easier. thanks again.

  • Graveyard Tech Apr 15, 2014

    Get the one with live data, you can freeze the readings. Maybe take a video of what little runtime you get

  • Graveyard Tech Apr 15, 2014

    Then playback what info you receive and watch for a drop in voltages, especially long term fuel trim. You could sell the other scanner to recoup some money.

  • Casey Jones
    Casey Jones Apr 16, 2014

    thanks for the suggestion im gonna get the new reader asap and see what it turns up. thanks again

  • Casey Jones
    Casey Jones Apr 19, 2014

    ok ive bought the new scanner and ive noticed that the ling term fuel trim is reading 0. what is that exactly

  • Casey Jones
    Casey Jones Apr 19, 2014

    theres a second reading on the scanner and ive noticed when it runs the longest the % of both fuel trims sometimes reaches 25% just before it dies and once i start it back up the voltage on the o2s11 rises and the truck smokes when it starts up

  • Graveyard Tech Apr 20, 2014

    Basically, fuel trims are the percentage of change in fuel over time. For the engine to operate properly, the air:fuel ratio needs to stay within a small window of 14.7:1. It has to remain in this zone under all the various conditions an engine encounters every day: cold start-up, idling in heavy traffic, cruising down the highway, etc. So, the engine computer is trying to maintain this proper air:fuel ratio by fine-tuning the amount of fuel going into the engine. As it adds or takes away fuel, the oxygen sensors monitor how much oxygen is in the exhaust and respond by telling the computer. The oxygen sensors could be likened to the computer's "eyes" that watch the mixture of oxygen in the exhaust. The computer monitors this input from the heated oxygen sensor(s) continuously when in closed-loop. If the o2 sensors inform the engine computer that the exhaust mixture is lean, the computer adds fuel by lengthening injector pulse, or "on-time", to compensate. Conversely, if the o2 sensors inform the computer that the exhaust is rich, the computer shortens injector pulse, adding less fuel to compensate in order to bring the rich condition down. This change in fuel being added or taken away is called Fuel Trim. Really, the oxygen sensors are what drive the fuel trim readings. Changes in o2 sensor voltages cause a direct change in fuel. The short term fuel trim (STFT) refers to immediate changes in fuel occurring several times per second. The long term fuel trims (LTFT) are driven by the short term fuel trims. LTFT refers to changes in STFT but averaged over a longer period of time. A negative fuel trim percentage indicates a taking away of fuel while a positive percentage indicates an adding of fuel. Think of it like this: You're driving from the beach at sea level into the mountains. On a short-term basis, you may go up and down several hundred feet at a time as you ascend the mountainous terrain. But, over the long-term, you are actually ascending from low to high altitude several thousand feet, gradually. It's similar with short and long-term fuel trims. STFT are immediate ups and downs in fuel, while LTFT are what is occurring over a longer period. A normal STFT reading will generally fluctuate between negative and positive single digits 2-3 times per second. Usually they'll stay around positive or negative 5%, but they may occasionally go up towards 8 or 9% depending on the efficiency of the engine, age of the components, and other factors. A normal long term fuel trim reading will appear to stay the same, giving a long term average of fuel added. It, too, should be close to zero, positive or negative single digits under normal circumstances. It will fluctuate much slower, possibly appearing static. Normal STFT Reading If you experience ST or LT fuel trims that are in the double digits positive or negative this would indicate a abnormal adding or lessening of fuel. This could be due to leaking fuel injectors, an unmetered air leak or something similar. For example, if the o2 sensors are reading lean due to, say, a vacuum leak, the engine computer will compensate by adding fuel. Lean STFT Reading The STFT will start to climb immediately to reflect the computer adding fuel. While the computer is adding fuel it still watches the o2 sensors until the o2 sensors are indicating that the lean condition no longer exists and proper air:fuel ratio is met. The computer will maintain this heightened addition of fuel until the leak is corrected. The scan tool will show STFT readings that are in the positive double digits, indicating that the computer has been adding too much fuel for normal operation. After a while the LTFT will also reflect this relative addition in fuel. Now if the vacuum leak is bad enough, the computer will not be capable of adding enough fuel to achieve proper air:fuel ratio. It will add fuel until the STFT reaches it's max calibration, usually 25%. Then a code is set in the computer indicating that the engine is running lean (P0171 or P0174) and the STFTs have maxed out. The opposite would be true if an engine was running rich due to a fuel leak (P0172, P0175). Rich STFT Reading Keep in mind that the computer has no idea if the o2 sensor is reading properly in some cases. For example if an o2 sensor was sticking rich, the computer would assume it was reading correctly and begin taking away fuel to compensate. This is referred to as a "false rich" condition. The computer would be leaning the engine and setting a possible P0172, P0175. The codes would indicate the engine was running rich but it ACTUALLY is running lean. If you use only the false rich codes to diagnose and don't observe all the fuel trim and o2 sensor data, you may make a false diagnosis. Also, each bank has it's own fuel trim reading. If your engine is a 4 cylinder, then it has only one bank, Bank 1. On a V-style engine you can isolate which bank is running rich or lean by watching that bank's fuel trims. If one bank is running properly, and another isn't you can narrow down a developing problem to one side of the engine or the other.

  • Graveyard Tech Apr 20, 2014

    Your injectors are dumping a lot of fuel!!!

  • Graveyard Tech Apr 20, 2014

    Have you changed the 02 sensors through the life of the vehicle?

  • Graveyard Tech Apr 20, 2014

    Have you replaced anything on the engine?

  • Graveyard Tech Apr 20, 2014

    You might have injectors stuck open letting an excessive amount of fuel into the cylinders. This will foul out the spark plugs, the unburnt/ compressed fuel will be a fog coming out of the exhaust pipe. In short, you may be changing the spark plugs , injectors and all of the 02 sensors.

  • Graveyard Tech Apr 20, 2014

    When you change sensors, on the engine, reset the ECU by removing both positive and negative terminals, from the battery, and hold them together for 20 seconds.

  • Casey Jones
    Casey Jones Apr 22, 2014

    i changed the front sensor last yr and ive replaced numerous parts such as the crankshaft sensor, water pump kit etc. the weird thing is about it all is the vehicle was getting but maybe 8 mpg and drove sluggish up until the weekend it died. it was almost like a vaccum or something unclogged or something cause tthat weekend i drove it 50 miles and barely moved the gas gauge. then that sunday was turning my truck around to change the oil and i died turning around in the road. and wouldnt start back up. i changed the crankshaft sensor and reset the timing. started right up and had a squeak. that was when it started the 15 sec run and then die. i then got a water pump kit including the w/p, timing belt, pullys etc. about two or three weeks before it died i had changed both exhaust manifolds, replaced the y- pipe that connects the exhaust. ive spent a pretty penny on this truck and im just ready to get some actual money making use instead of high parts bills. the main thing that has stumped me the most is the fact that it fires right up everytime but then dies and throws no codes.

  • Casey Jones
    Casey Jones Apr 22, 2014

    thank you so much by the way for taking the time to help me with my truck issues. all the knowlege i can learn will better help me in the future and i thank you.

  • Graveyard Tech Apr 22, 2014

    You are very welcome!

  • Graveyard Tech Apr 22, 2014

    The front two (02) sensors could be bad again, I'm not sure. But, the proof is that it is capable of running, we just have to track what is shutting down during the 15 second window.

  • Graveyard Tech Apr 23, 2014

    On the fuel rail should be a relief valve, much like a tire stem. Take out the valve, use 4 to 6 feet of exact size fuel line, put one end over that relief bung( with a hose clamp) the other end into a gas can, then turn on the key and let it pump. We'll see if it pumps rel good for a while. For a test!

  • Casey Jones
    Casey Jones Apr 23, 2014

    i tried checking the data today and i realized the voltage on the number two o2 never changed from .02v. the reading of the first o2 varies around .06 but does change..

  • Graveyard Tech Apr 23, 2014

    The front should change from.200 to .700( front one might not be working properly)

  • Graveyard Tech Apr 23, 2014

    Add a CommentFirst, remove the O2 sensor, thrn degrease the bung that it mounts into, clean it and sand it wit 180-240 grit, clean it with alcohol and reinsert the O2 sensor! See if it changes in readings. The back O2 (after the Catalitic converter) won't change untill heated, around 20 minutes or do

  • Graveyard Tech Apr 23, 2014

    Add a Commenor so

  • Graveyard Tech Apr 23, 2014

    Chech the O2 sensor to see if it's white in color, if it is replace it.

  • Casey Jones
    Casey Jones Apr 23, 2014

    so i tried again today and yes the front sensor went up to around .20 but that was as high as it got concidering it only runs for a few seconds. i took the front one off and all looked fine. i also took the back one off and looked at it and it barely had any carbon on it. im actually breaking down and concidering taking it to a shop. this computer issue mess has got me more stumped than i can take. sucks too, parts are expensive enough and finding a trustworthy mechanic is hard to come by. thats why i do my own work. i just cant believe this truck with all these sensors, the check engine light is not flashing. im stumped.

  • Graveyard Tech Apr 23, 2014

    Hats off to ya, I totally understand! I do my own work as well so, I know what you mean! It took me two months to trace the problem with my5.4 Ford. I couldn't stand the $78.00 an hour investigative work on mine, I had to do it myself. I hope it is a simple fix! Let me know what they find out, okay!

  • Casey Jones
    Casey Jones Apr 24, 2014

    yea i cant stand it either. ive already replaced so much with no luck. ive just been three weeks w/o my truck and i cant stand to be without my ride. thanks again for all the help. i'll sure keep posted on what it turns up to be so maybe you could pass it along to someone else in need.

  • Graveyard Tech Apr 24, 2014

    Try one more thing! I've seen a lot of problems that have ended with a bad master cylinder. If you get a vacuum gauge. Hook it to a vacuum line, run the truck for its short time, once it dies watch to see if the vacuum bleeds off.

  • Casey Jones
    Casey Jones Apr 26, 2014

    i will look into that. that for sure sounds like an "out there" problem that i would end up having wrong. thanks for the idea ill try it out.

  • Casey Jones
    Casey Jones May 25, 2014

    well it took long enough but i got the truck looked at and it turns out the computer had been submerged at some point. i dont know if my luck had anything to do with it but at least i know or at least hopefully pointed in the right direction. he said all my sensors and relays tested fine so it let him to the computer. when purchasing another computer does it make a differance that the vehicle is 4wd or would any 3.0 computer work?

  • Graveyard Tech Jul 03, 2014

    Computers should work the same, 4-wheel is from 12volts best of luck!

  • Casey Jones
    Casey Jones Aug 17, 2014

    well it turns out the 2wd does have a differant ecu. i ended up buying another truck for parts but im thinking that my ignition advance is to far. i drive the vehicle and after a while it misfires, throws a code for multiple misfire malfunction, but only does it once or twice during a 5 mile drive. the ign adv says its advancing upwards of 40 degrees and i set the timing marks on tdc when i replaced timing belt. how would i go about dialing advance down because im also smoking real bad at low rpm.

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