Mitsubishi Diamante Maintenance and Repair

tmiccichetmicciche Member Posts: 1
I have been told by the dealer that my heater core needs to be replaced. It was leaking antifreeze onto the passenger side floor. The car only has 45,000 miles on it so this seems like something that may have been a manufactors defect. I was wondering if anyone else had this problem and if mitsubishi had recalled this part.


  • msmdiamantemsmdiamante Member Posts: 3
    Please help? Ms Molly Diamante won't start. She's a '93 with DOHC V6 just like many 92-95 Diamantes and 3000 GT's. We made her battery go dead. We had her battery tested and charged. It's ok. Everything works, lights, radio, etc. However, when we turn her key. She clicks once and doesn't even try to turn over. She ran just fine before we ran the battery down. We have activated, set off, and de-activated her alarm. She still won't start. Please anyone? Can you please tell us how to get her started? Do we need to pull a plug or press a button to reset her ignition from being locked by the alarm?
  • mikeshaftmikeshaft Member Posts: 1
    I too have 2001 Mitsubishi Diamante, and I heard from
    different Diamante owners complain about their heater core had to be replace. I have 55,600 miles now and thank God
    I have met that problem yet but I had to replace two of my engine mounts . That cost me 563.00 at the dealer. The
    other day I had to replace the head gasker that was leaking, thank God that was under the power train warranty
    and also replace the oxygen senor. Last year the steering rack wwnt. That cost me $1500.00. Only , I almost forgot the tranmission pump seal has to be replace, that was under the power train warranty. This car ride nice, but never had a car break down so much. Hopefully in two years
    I will buy an Honda Accord. Mitsubishi sucks. I need a car that will lastme. I suggest you trade your car in for a Honda Accord or Toyota Camry. You can't go wrong. These cars have no resell value.
  • mrcamfmrcamf Member Posts: 1
    I was wondering if someone else has experienced the same problem....last week I turned my car on and the check engine light came on. Also when I looked at the dashboard, the indicator that tells you what gear you're in started switching in between neutral and drive. I drove my car to work and instead of it taking off when I hit the gas, it feels like it's sluggish, like something is holding it back. I figured it was a transmission problem, so I took it to a repair shop that specialized in those problems. The place I took it to told me that the car locked the transmission in 2nd gear for whatever reason, and that they wouldn't know what the real problem was until they physically removed/ inspected the transmission itself for 400 dollars. Before I hand someone half a grand, has anyone else experienced the same problem? Should I go to the dealership??? Any advice or opinions would be appreciated. Thanks in advance.

    C. Foster
  • tlyetlye Member Posts: 1
    Have a 98 Diamante, heater core leak at around 38K to 40K miles, was cover by extended warranty.
  • mike2002diammike2002diam Member Posts: 1
    Hey, did you find out what the problem was? I've just gotten the same thing on my 2002 Diamante, and if you know what's wrong it would make things easier for me as well. Thanks for any info you have.
  • precise86precise86 Member Posts: 2
    is it a first gen Mitsu Diamante? If it is it has a HISTORY of a failing TCU (Trans. Control Unit). there are articles complaining of relays and diodes in the tcu failing ALL th Time. Its like a serious issue with these types. Unfortunately by the time the TCU fails, 99(% of the time the warranty for the vehicle has runout. Getting a new one from the dealership WILL cost u an arm and a leg. Mine is in the same dilemma and I an still trying to find one on the net.
  • hlgramjrhlgramjr Member Posts: 2
  • hlgramjrhlgramjr Member Posts: 2
    Transmission Control Unit
    A Transmission Control Unit is a device that controls modern electronic automatic transmissions. A Transmission Control Unit generally uses sensors from the vehicle as well as data provided by the Engine Control Unit to calculate how and when to change gears in the vehicle for optimum performance, fuel economy and shift quality.

    Electronic automatic transmissions have been shifting from purely hydromechanical controls to electronic controls since the early 1990’s. Since then, development has been iterative and today designs exist from several stages of electronic automatic transmission control development.

    The evolution of the modern automatic transmission and the integration of electronic controls have allowed great progress in recent years. The modern automatic transmission is now able to achieve better fuel economy, reduced engine emissions, greater shift system reliability, improved shift feel, improved shift speed and improved vehicle handling. The immense range of programmability offered by a Transmission Control Unit allows the modern automatic transmission to be used with appropriate transmission characteristics for each application.

    Input Parameters
    The typical modern Transmission Control Unit uses signals from engine sensors, automatic transmission sensors and from other electronic controllers to determine when and how to shift.

    Vehicle Speed Sensor
    (VSS) This may also be known as an output speed sensor (OSS). This sensor sends a varying frequency signal to the Transmission Control Unit to determine the current shaft speed of the output shaft or differential in a typical vehicle. The Transmission Control Unit uses tire size, gear ratios and final drive ratio to calculate the current vehicle speed.
    Turbine Speed Sensor
    (TSS) This may also be known as an input speed sensor (ISS). This sensor sends a varying frequency signal to the Transmission Control Unit to determine the current shaft speed of the input shaft or torque converter. The Transmission Control Unit uses this shaft speed to determine slippage across the torque converter and potentially to determine the rate of slippage across the bands and clutches.
    Transmission Fluid Temperature
    (TFT) This may also be known as Transmission Oil Temperature (TOT). This sensor determines the fluid temperature inside the transmission. This allows the Transmission Control Unit to modify the line pressure and solenoid pressures according to the changing viscosity of the fluid based on temperature. This can provide for more appropriate shifing in extreme temperatures and allow for temperature failsafe systems to take control.
    Output Parameters
    The typical modern Transmission Control Unit sends out signals to shift solenoids, pressure control solenoids, torque converter lockup solenoids and to other electronic controllers.

    Shift Solenoid
    Modern electronic automatic transmission have electrical solenoids which are activated to change gears. These solenoids range from very simplistic control in older automatic transmission designs to extremely complicated in very new automatic transmission designs. The way in which the soleniod is activated and when it is activated is chosen by the manufacturer of the transmission and can vary greatly from vehicle to vehicle.
    Pressure Control Solenoid
    Modern electronic automatic transmissions are still fundamentally hydraulic. This requires precise pressure control. Older automatic transmission designs may only use a single line pressure control soleniod which modifies pressure across the entire transmission. Newer automatic transmission designs often use many pressure control solenoids and sometimes allow the shift solenoids themselves to provide precise pressure control during shifts by ramping the solenoid on and off. The shift pressure affects the shift harness and shift speed.
    Torque Converter Clutch Solenoid
    (TCC) Most electronic automatic transmissions utilize a TCC solenoid to lock the torque converter electronically. Once locked, the torque converter no longer applies torque multiplication and will spin at the same speed as the engine (assuming the converter is fully locked). This provides a major increase in fuel economy and modern designs attempt to provide partial lockup in lower gears to improve fuel economy further.
    This entry is from Wikipedia, the leading user-contributed encyclopedia. It may not have been reviewed by professional editors (see full disclaimer)
  • deavendeaven Member Posts: 1
    Where is the internal Check Engine Light connection? Auto zone offers free Check Engine Analysis, but could not locate the connection to plug in their "meter". Does anyone know where it is located?

    I was told the the Check Engine light can come on if the gas cap is not fully tight. In that case once the cap has been tightened will the check engine light go off or does it have to be reset?
  • diamoneydiamoney Member Posts: 13
    I had the same deal with my Diamante.. Last January,and the connection is behind that little clip on the dash next to the sterring column.. I had to replace two timeing sensors and also the CO2 sensor.. Not a cheap fix, nor a quick one..

    Back to the heater core guys.. Yeah, I have a 2000 LS and I also had to replace my heater-core at about 60K.. Not a cheap fix.. especially in the dead of winter..

    Anyone know how much work it takes to replace the front rotors.. I replaced the pads last fall with lifetime ceramics, but I know the rotors need to be swapped.. LOTS-O-GRINDING..

    Muchos gracias..
  • diamoneydiamoney Member Posts: 13
    One more note, my rig also has an intermittant issue with on/off ramps.. It will seem to under-steer (from the back), if I make any sort of movement when continuing through an on/off ramp. I am not going excessivly fast, but it seems to want to sway left to right, sort of from the back.. almost to the point of loosing control.. And if I drive on Ice or snow, it seems to want to come out from under me, (fish tail of sorts) Could I guess at it? sure, maybe the rear struts, wheel drag, tires?? any help would be appreciated..
  • Mr_ShiftrightMr_Shiftright Member Posts: 64,481
    Try pumping the rear tires up (only the rears) to 2-5 lbs over suggested, just as an experiment. You might have tires with very compliant sidewalls. The rear struts would have to be pretty much blown for them to contribute to that, but you are on the right track with that as well.
  • diamoneydiamoney Member Posts: 13
    I usually run my rubber near the max posted on the side-wall.. (so close to 35-50 lbs) what is your next idea.. I tried to run less.. but it wants to get worse.. it is fine in the summer/dry-stuff... but if I hit the snow/rain.. it gets a bit exciting.. maybe new rubber???? your thoughts...
  • Mr_ShiftrightMr_Shiftright Member Posts: 64,481
    are these factory original tires? How many miles on the car?
  • diamoneydiamoney Member Posts: 13
    I bought the car in 2002 and have only replaced the front rubber.. It had 56K on it when I bought it, and now shes turning 96K.. Not sure if they are factory or not, but I would not think so.
  • Mr_ShiftrightMr_Shiftright Member Posts: 64,481
    Well at those miles you could definitely be considering rear struts. As for the tires, you'd need a tire shop to judge how strong the sidewalls are and how good the tires are. There's only a few ways the rear of the car can move around like that---weak sidewalls, worn struts, or some really loose bushings in the rear suspension (something fairly obvious).
  • jefany4jefany4 Member Posts: 8
    i bought this mitsu dia 94 with an infiniti car stereo(factory installed),when i turn it on it keeps asking for a code or it wont work...............i dont have a clue as to removing it for a serial number........any help on this
  • Mr_ShiftrightMr_Shiftright Member Posts: 64,481
    You'll have to ask the Mitsu dealer but you may be out of luck on this because it's so old...or if you can find the seller ask them if they wrote the code down somewhere in the owner's manual.
  • littlestsqawlittlestsqaw Member Posts: 1
    I am having the same problom and mitsubishi diamante did not come with owner's manual so what i do
  • cumbiamocumbiamo Member Posts: 2
    Have a 94 Diamante with 156 K bought with 17K on it. One of the bolts from the front tire has broken off and needs to be replaced. The shop says it will be $90 for putting in a $4 bolt. Is this something I can do myself. I know it involves taking the caliper off ? Not worked on cars before but with Xmas trying to save. Thanks
  • misty25misty25 Member Posts: 2
    I have a 93 Mitsubishi diamante and the other day I was getting ready to leave for work and the car stated the shut off then the same again then it just kept turning over but not starting so i waited a few minutes tried it aging it stared then shut off. Later that night when I got home I tried it again and it stared just fine today as well but I don't know what the problem is and i don't know how to find out. I only payed 500 for the car to start with so I don't want to spend more than that just to diagnose it so if anyone has any suggestions please let me know.
  • 88oldscutlassc88oldscutlassc Member Posts: 1
    Front rotors are generaly an easy job on any car for any backyard mechanic.How much did the heater core job cost,mine just went on a 2002 Diamante.It has about 53k miles.
  • rockinout88rockinout88 Member Posts: 2
    Ok i have a similar car, i dont know whether yours is DOHC or SOHC but i doubt that makes a difference. To solve my problem I had to change the battery and altenator.
  • rockinout88rockinout88 Member Posts: 2
    I have a 93 model... i took the time to call the dealership to find out how to get the code. You will laugh at this, they want you to take it to the nearest dealership and pay 45 bucks to take out the stereo to get the code, or you could take out the whole dash unit to get the serial number on top of the stereo unit and call it and then they will give you the code
  • jefany4jefany4 Member Posts: 8
    you dont need remove the dash to get the stereo out........remove cent coin tray by shifter then 2 screws in the hole,then side of center console screws..then move shifter back as fas as can then stereo should be removable......find parts number and call mits. dealer get parts dept. and tell parts dept. the stereo part number and they will give you the code!
  • jefany4jefany4 Member Posts: 8
    or go to this site for removal instructions.....hope it helps!
  • jefany4jefany4 Member Posts: 8
    hi misty,
    it could be as easy as the battery cables!
    check that all connections are clean at all the connections to the battery and the block!
    check both ends of the black cable(negative)
    check both ends of the red cable(positive)
    most times if the negative cable is loose you will experience this........i have and cleaned all connections and went from there.........good luck!
  • misty25misty25 Member Posts: 2
    I had the battery check its fine. but the other night while i was driving it the engine shut off i waited a few min got it to restart drove it a short distance then shut of then restarted drove for a while puttered then shut off then restarted and i was able to get it home haven't driven it since then cause don't know whats going on. anyone have any suggestions?
  • ss4elass4ela Member Posts: 1
    I had a similar prob w/my 92 LS, except mine would run 4 about the first 45 min (when cold) in the am, then stall,would not start until it sat and cooled 4 about 15 min. then would run 4 another 5-10 min.Mine turned out 2 be the ECU.(Engine Control Unit). Found 1 online for 425.00(joined Planet Salvage). But yours sounds like a possible fuel pump problem. As an auto tech, I have seen this symptom more than a few times leading to the electic fuel pump. Pump is universal, so it is fairly inexpensive,but is located in fuel tank,high labor. easy 2 diag.-just have mech. friend install fuel pressure guage, make sure its up 2 spec.,& make sure it holds steady pressure w/key on. if not,replace. Hope this helps,E
  • jerryterry22jerryterry22 Member Posts: 9
    I had antifreeze leakage on the driver's side carpet, odor and residue on inside of the windows -fog. (2002, 6 cyl., 3.5 liter).

    The Mitsubishi Service "greeter" told me the the heater core was on the passenger side and that the dampness under the driver's feet might be from a hole - going through water!

    I had a mechanic who fixed only heater cores replace it.
    He told me he had to remove the entire dash and huge number of fasteners.
  • diamoneydiamoney Member Posts: 13
    I had the same thing happen right when I picked up m rig.. (2002) they made me pay for parts, but the labor was picked up.. any yeah, it does not sound like a fun one..
  • diamoneydiamoney Member Posts: 13
    I have a 02 Diamante, anyone ever install an XM/Sirius radio in their rig? If not, know anyone who may have taken on this task?
    My question is this, what hardward did you need and where did you install it?
  • ldelaneyldelaney Member Posts: 4
    Just before I stop, the transmission does a hard downshift and sometimes lurches forward. Major transmission company overhauled but still does same thing only not as bad. They reflash the tranny, works fine until shut off, then does same thing when restarted. What gives? :mad: :confuse:
  • manybrewsmanybrews Member Posts: 3
    that is due to worn lower "pillow" bushings in the rear knuckle.
    they can be replaced seperatly.
  • crobertsoncrobertson Member Posts: 2
    I recently bought a 03 Diamante (which I dearly love, so far). I had to get the owners manual myself, but it doesn't give the recommended mileage for maintenance, only what to do and how to do it. would someone happen to have
    that info, it surely wouldn't be very much. I've already tried the maintenance program from edmunds, they don't have any info. I sure would appreciate it!!
  • diamoneydiamoney Member Posts: 13
    Heater core was between 400-500 bucks..
    I did the rotors on all four, and replaced the pads in the back for under $200.00, and about 2 hrs..

    In response to my previous issue, the rear nuckle bushings were replaced and solved my problem.. apparently it is pretty standard on these cars.. $400.00 at the stealership.
  • diamoneydiamoney Member Posts: 13
    As the seasonal temp rises my car starts to act up a bit. In stop/go traffic on a warm/hot day, my cars idle will slow almost to a stall, then jump back up.. If I put it in neutral, it stays fairly steady, then I pop it back in gear when I need to advance. I have a little less of an issue if I switch the A/C off, but then I sweat my balls off..

    Any suggestions?? I was thinking I should replace the plugs.. I have at least 60K on them..
    If that is a good idea, how do I get to these.. I can't seem to see them when I pop the hood..

  • tonga1tonga1 Member Posts: 1
    I have a Diamante 1994 .It has a GA 12 engine, model E F12A TRHE and Chassis No F12A-3009787.

    The engine starts than after a while the engine starts to get slower and then it stall.When I pop tthe gear into parking or reversing it doesn't go anywherre.It has a rattling sound underneath the machine when it does this..Please Help
  • ldelaneyldelaney Member Posts: 4
    :confuse: Hey, the major company had to replace the tranny and tcm to fix the hard downshift problem.
    Have another problem that actually predated the tranny. 97 Diamante starts fine first thing in the am and then is hard to start most of the day after that. Replaced the IAC, MAF, throttle body, egr valve, vacuum lines, spark plugs, distributor cap, TPS and a couple of other things that I can't remember. Has an erratic idle also, sometimes around 800 then up to 1800. When it is around 1800, you can bet it will die and be hard to start. Any ideas?
  • jbnc1jbnc1 Member Posts: 1
    I bought my D in Oct. of '05, since then i've been replacing original parts about every 90 days. Last week it started running hot til one morning I was driving it on the hwy when it shut off when I took my foot off the accelerator. I have now learned that the intake gaskets were melted down to the metal allowing the fluids from the radiator to drain into the exhaust. I've had the gaskets changed, heads and valves checked, replaced the timing belt and etc., new spark plugs and wires, and new fuel filter. When I attempt to start it, it is still spitting fluids from the tail pipe. what else must be done to start her up?
  • jbooth5jbooth5 Member Posts: 1
    I have a problem with this annoying clicking sound when I start my Diamante. It only last for about 20 seconds, and it goes away. If I turn the temperature dial above 70 degrees, the clicking sound stops. If I turn the temperture below 70 degrees, the sound starts clicking. Does anyone have any ideas of what my problem might be?
  • diamoneydiamoney Member Posts: 13
    If you have automatic climate control, more than likly your bearings are going out on your blower-fan. I have had the same deal happen in other vehicles where the fan would not come on until you tapped the motor on the fan. You can deal with the 'chirping' or replace the fan or fan motor.
  • jefany4jefany4 Member Posts: 8
    here's my question..........when i use the key to open the doors(factory installed alarm)the locks open then close so quick i cant get in unless i use one hand to unlock and the other to pull the door open.........i have no remote........just the key.
    is their a cure to stop this rapid lock.......its annoying in bad weather.............thanks,Jeff
  • mdfallmdfall Member Posts: 1
    Hello all
    I have problems with my alternator. It is over charging the battery (which gets hot to a boiling point). My friend who is mechanic helped me replace the Alternator and the battery. I have both of them new. Now despite the new parts, the issue keeps coming back. I had to replace a second time the alternator and the shop agreed to give a new battery too. Today the mechanic told me that he needs to replace the Battery Relay (located in the fuse box).

    On top of that, when I drive the car on the highway (60 mph), the car over heats. When it is stopped and on idle it looks normal. Are the issues related? Please help me come up with a solution. Thanks.
  • mojicamojica Member Posts: 6
    i can put my vehicle on jackstands and it will go through all the gears and run great,but i can put pressure on the lead tire and it will act like it is slipping. any ideas if i need a new tranny or just some kind of sensor or solenoid? any ideas would b appreciated.i do plan on flushing all tranny fluid out of system first maybe,just maybe it will catch some gears,it does have a funny electronic whinny noise coming from pan,hoping it is just electrical.any idea would be great
  • mojicamojica Member Posts: 6
    i can put my vehicle on jackstands and it will go through all the gears and run great,but i can put pressure on the lead tire and it will act like it is slipping. any ideas if i need a new tranny or just some kind of sensor or solenoid? any ideas would b appreciated.i do plan on flushing all tranny fluid out of system first maybe,just maybe it will catch some gears,it does have a funny electronic whinny noise coming from pan,hoping it is just electrical.any idea would be great
  • mojicamojica Member Posts: 6
    i have same car,leave car on,if it still says code on radio with the first 4 memory buttons1-4 type in code 7707. example #1 button press till it hits 7,#2mem button press it till it says 7 and do the rest 4 the other 2 mem buttons,then press your tape button,which on mine is an > symbol then your radio will kick on.if the (off) code is on you must leave your car on 4 an hour to get (code) back will only give 3 chances 4 this,this only works on mistubishi radios,if u have an infinity radio u need to still give vin# and serial # of radio,which is why they wanna cahrge 45 dollars to do code,removal of radio.
  • jtkramer6jtkramer6 Member Posts: 1
    I have a 1997 Diamante with same issue (100k miles). Mine was carbon in the engine which I removed with SeaFoam which you can buy at Autozone for about $7. I sucked the SeaFoam up through the PCV Valve (pour in bowl and do this slowly, so engine wont die) while I jockeyed the throttle cable under hood (to keep engine from dying) to get all of it sucked up into engine intake. After all is sucked up, turn off car for 5-10 minutes and restart. It will smoke out the tailpiple like crazy for 10 mins (your neighboors might call fire dept from all the smoke!), but should smooth your idle if carbon related. My idle was smooth as glass not right after this cleaning, but after several days of driving. Seafoam is oxygen and catalytic conventer safe and will actually clean the converter, too. Your plugs should be of the 100K mile variety, but if cheap gas, carbon may be your issue. You may have also have EGR issues and check that valve and/or blockages, too. Decarboning intake and ports will help as well if you have EGR 403 code that is flagging/service engine light on. To change plug, you must remove the plenum, not as daunting a task as it seems, remove black plastic cover, bolts through plenum to block and you don't even have to remove airbox/flowmeter; leave attached and just pry/left up just out of way (but not too far too crack rubber hose from air box to plenum) to get to plugs, if truely foiled/need replacing. Replace plug wire at same time while you are in there. Good luck!
  • diamoneydiamoney Member Posts: 13
    Thanks man.. I will give it a shot..
    I actually went in and cleaned the throttle body, and valve.. It was a little tight in there, but I was able to smooth it out considerably...
    In regards to the plugs.. you were speaking about the spark-plugs correct? if so, can you clear it up for me.. I still am boggled about how to change them.. do i actually have to remove the upper to get at the rear plugs??
    any help would be appreciated..
  • diaman94diaman94 Member Posts: 1
    I have a 1994 Diamante LS, not Calif. equipped. I recently purchased the vehicle used with 135000 miles on it. The vehicle has received regular maintenance in the past (The former owner is a close friend). Following a fluid check and simple cleaning of the engine compartment yesterday (11 Oct 07), the vehicle started fine, and ran smooth. Soon thereafter, however, it began to idle very roughly, and the check engine light came on. The vehicle still runs, but has experienced a noticeable loss of power and acceleration, and continues to idle poorly. During the cleaning operation, I did manage to spray some water under the hood, but not in any excessive quantity. I am at a loss to explain this sudden loss of power and rough idle/check engine warning. Any ideas you can provide would be greatly appreciated.

    Thank You!
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