Mitsubishi used less than top quality ECU Capacitors for several Years.
If you have a 91-93 car the capacitors in the ECU are at high risk of failure.
94 and later cars have different capacitors and after selling amost 100 sets of
capacitor not one customer reported problems with a 94 or newer car. About 10%
of the 91-93 ECUS had capacitors that showed signs of leaking. The remaining ECUs
only had capacitors changed as a safety precaution.
If the Capacitors go bad the ECU will start acting funny and eventually burn
out completely. Rebuilt ECUs are from $250-$450 but only if one is
avialable most places do not actaully rebuild yours they just send you another
ECU. Investigate the ECU reapir place beacuse many do not repair ECUs at all
thye just give you a used ECU and a warranty. This is because so many mechanics
do not understand electronic so they just replace parts until the car works.
Most defective ECUs sent to repair shops are actually good, so some repair shops
inspect the ECU and if it is good they sell it to you as "repaired" with out
actually doing anything to them.
Complete list of ECU Part Numbers
I mined the dealer parts program to get EVERY ECU for domestic 3000GT and Stealths.
Use this list to make sure you don't get the wrong ECU.
For a complete list of ECU
Part Numbers Click here!:
Instructions on how to do the actual repair
TechnoMotive publishes great instructions on
how replace Capacitors on 1st Gen DSM ECUs.
3000GT/Stealh ECU can use exact same parts and instructions.
Technomotive gives the following warning signs for Bad
capacitors in ECU.
- A rapid clicking or chattering from under the dash. Usually accompanied with
the engine stalling or losing power during the noise. This is the microcontroller
going into reset over and over and over again due to a bad power supply. Every
time it resets, it will turn the fuel pump relay on and off. This could also be
a bad fuel pump relay, but not usually.
- An usual smell that seems to come from the center console. Especially if i
smells like rotten seafood. Consider that it could also be your heater fan motor,
unless accompanied with a power loss or stalling.
- Your car is older than seven years and sees a lot of extreme temperature
transitions. If you experience either of the first two problems above, act
on them as soon as possible. Even though your car may still be drivable, the
longer you let the problem go the more likely you will end up with a hole
in your ECU's PC board or with several blown components on the board. Then you
will have to dig a unit up in the junkyard or buy a new one from Mitsubishi
Digikeys sells the capacitors but charges around $10 for shipping and handling.
I used to sell capacitor sets but it took up too much of my time.
This thread has lots of great information and feedback from people who repaired
thier own ECUs.
3si Thread about Capacitor replacement
See picture below for ECU location. The 3 yellow connectors used be hooked to ECU.
I had the ECU out at time of this picture.
ECU Removal Instructions
To remove your ECU go to Jeff Lucius' webpage listed below. He has excellent directions.
Feedback from some people who have replaced Capacitors
Please note: were emails have been cut down to save space I added periods... :
.....I installed them on Saturday, two of the old ones had leaked a
little. The whole thing took about 1-1/2 hours (the old caps didn't want to come
out) and was a complete success..... it was mainly preventive, but I had noticed
a couple of problems that may or may not have anything to do with the ECU, figured
that it couldn't hurt though. I think that it actually may have gotten rid of a
warm idle problem, but only time will tell with that because it was very sporadic.
I Just installed the caps.. not too hard.. I managed to do it all within 2 hours..
twas my first time desoldering anything. Wanted to be extra careful not to screw
up. Installing the caps took me 5 min.
noticable difference? HELL YES!
no more funky idle
no more hesitation, pulls like a SOB like it should
overall.. it solved a bunch of the "little" problems the car had.
looking at the old caps, yeah they were starting to leak, underneath the caps
which is sometimes hard to see was this brownish goo. not too much, but enough
to make me worry. Fortunately the crap didnt eat thru the pcb or do any serious
I would have to recommend this to anyone with minor problems that they cant get
I have a 91 stealth and the caps NEEDED to be replaced.. Id say if your over
say the 7 year mark, pull your ecu and give it a good look to see what condition
your caps are in.
Date: Tue, 04 Dec 2001 10:47:18 -0600
From: "Mark Wendlandt"
Subject: RE: Team3S: ECU problems, part II
As has been discussed, leaking electrolyte is one of the problems with
aluminum electrolytic caps. It is not a mitsu specific problem! They use a
rubber-type seal on the bottom of the cap that ages with time/heat, etc. and
will allow the electrolyte to leak out on to the PWB. This electrolyte is a
salt solution. Everything will evaporate except the salt which is very
corrosive and conductive. This is where we start to have problems. We can
get shorts but also large voltage spikes that can damage ecu components
because of the lack of filtering.
As and electrical engineer for Honeywell, we cannot design aluminum
electrolytic caps into any military products because of their shelf life
requirements(i.e avionics sitting on the shelf for many years before needing
to be used during a time of war...)
One solution might be a solid tantalum cap, but you might have to use more
than one tantalum to replace one electrolytic because of voltage/capacitance
requirements. You get the most bang for the bug with aluminum electrolytics
when talking about voltage, capacitance and package size.
Do a google search on leaking aluminum electrolytic capacitor and you will
get hundreds of pages on the subject(big problem on older stereo
Just replace them with new aluminum electrolytics and you will get another
7+ years of service.(I've got 10+ on my '91 with original caps). It is
something that we all have to live with from VCRs to Camcorders to our