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Good afternoon guys. What all is involved with changing out the ECM on a 1995 SL? Can I simply just install the new one and call it a day or does the dealer need to program it to my certain vehicle? Thanks for any advice!
 

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No programming required, but you do need correct ECU number that’s shown on top cover. Or have yours rebuilt.

This link shows how to remove yours.
 

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As stated, no programming needed. 2G ECU failure is not nearly as common as 1G. I would want to check all the output devices for problems before I installed a replacement. Make sure there isn't something going on in the car that will damage the new one.
 

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As stated, no programming needed. 2G ECU failure is not nearly as common as 1G. I would want to check all the output devices for problems before I installed a replacement. Make sure there isn't something going on in the car that will damage the new one.
Do you know off the top of your head what items would damage the ECU? I have heard that the ISC/IAC can damage an ECU. Anything else that I need to look out for? Thanks.
 

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Anyt
Do you know off the top of your head what items would damage the ECU? I have heard that the ISC/IAC can damage an ECU. Anything else that I need to look out for? Thanks.
Any output device the ECU directly controls... These are mostly items powered by the MPFI relay, and grounded by the ECU to energize them. That list includes IAC, injectors, any emission or other solenoids, VIC motor, etc.

Any such device that fails to an open circuit simply won't work, and will cause no damage. Any device that fails to a direct short, (thankfully rare) will let the smoke out of the driver circuits in the ECU.
 

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From your ignition thread and this one, seems you have a stalling problem and are making assumptions and asking questions based on them. You might have better results if you gave details on how and when car stalls for others to suggest best procedure of what and how to check.
 

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From your ignition thread and this one, seems you have a stalling problem and are making assumptions and asking questions based on them. You might have better results if you gave details on how and when car stalls for others to suggest best procedure of what and how to check.
Thanks for responding guys! Yeah I’ve been making assumptions based on info I’ve read and some experience I’ve had with other vehicles. I will list below the details and issues that I’ve been having.

I bought the car back in January and drove it for about 3-4 weeks without any issues. Then one morning when the temperature was about 33-35 outside the car wouldn’t start, it would crank over but not start (could wait a few minutes or days and it would start). I took it to a shop and they looked over it and said they weren’t sure but they believed it was the ECU (didn’t hold much weight since they didn’t even take it out and look at it). This same shop put in a coolant reservoir as it was leaking. On the way back on the interstate going 70 the car just shutoff. I waited a couple minutes and it started up again and drove home. The trip was about 5 miles and the car shutoff on me 3 times. Battery, alternator, and starter are all good per Autozone test. Ole Catfish at Autozone mentioned it could be coolant temp sensor and since it’s cheap I installed it Saturday morning. Car drove good all weekend and all week until today it shutoff on me twice. Haven’t had the tough starting issue since, I believe, it’s been warm but now car periodically shutoff/stalls. Tested compression in front 3cylinders and they’re good at 160. Will test rear cylinders this weekend. Will be doing a block leak test just to somewhat know if head gasket issues. The car does have a slight shimmy at idle so not sure if it’s a miss, fuel issue, ECU, etc and Idon’t know for sure if the stalling and shimmy are related. I will check ignition/screw at column and pull out ECU to see if it’s damaged. Previous owner changed items below within the last 15,000 miles: coils, plugs, wires, crank and camshaft sensors (duralast brand), fuel filter, regulator, injectors, ignition control module, idle air control module, alternator, harmonic balancer, timing belt and water pump. I know it could be a lot of items causing my issues so I’ve been trying to find the most logical fix and work from there. Thanks and sorry for rambling.
 

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Discussion Starter #9
Anyt

Any output device the ECU directly controls... These are mostly items powered by the MPFI relay, and grounded by the ECU to energize them. That list includes IAC, injectors, any emission or other solenoids, VIC motor, etc.

Any such device that fails to an open circuit simply won't work, and will cause no damage. Any device that fails to a direct short, (thankfully rare) will let the smoke out of the driver circuits in the ECU.
Thanks RealMcCoy. Very informative answer, I appreciate the help!
 

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Good write up covering details of your problem and what has been done to this point. Since your problem is erratic and unlikely to show when testing as RealMcCoy suggested, it’s going to be harder to locate. I now see why you were mostly working from assumptions. Also you need to keep in mind items replaced by previous owner, although few miles since done don’t eliminate them from being the problem because of parts quality these days.

To me the key points of your write up is fact that engine will quit at any time and restart shortly after, also it may do it few times in a row. Need to find way to determine if spark or fuel lost at stall point. What would be nice is a in car fuel pressure gauge (even if temporary) that when engine stalls while driving a quick glance at gauge would answer if pressure was lost.

In meantime maybe try to pull any stored codes from ECU looking for possible clue.
 

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......The car does have a slight shimmy at idle so not sure if it’s a miss, fuel issue, ECU, etc and Idon’t know for sure if the stalling and shimmy are related.....
Couple things you could do to possibly narrow this down.
1) While idling pull one spark plug wire from coil at a time to see if it gets worse or no change. If no change when one is pulled you’d know that cylinder has a problem (at least at idle), then troubleshoot components to that cylinder which might lead to overall problem.
2) While idling spray starter fluid around intake manifold, plenum edges and any spot vacuum could leak. If engine smooths out or speeds up, you’ll know you have vacuum leak there.
 

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Sorry guys, been working on a lawnmower for 2 days and been in Cub Cadet mower mode. I definitely appreciate your response and I believed you nailed it in your response and I should be able to pinpoint the problem with trying what you mentioned! I would like to test the fuel pressure but these cars don’t have test ports. I’ve thought about intercepting the line before regulator? The vacuum idea I didn’t even think about and can be a few other items, The car did throw a code a while back but the shop guy said he adjusted a wire and the code hasn’t been back. This was way before the stalling and about a week after the no start issue in cold weather (code 36 ignition timing adjustment signal fault). I really think the issue is either ECU, fuel pump, PTU, or something associated. It could be the Duralast crank and camshaft sensors, I wanna say I read some items are preferred to be Mitsubishi OEM. I will run some of those tests tomorrow (got all day her) and maybe take out ECU if nothing is obvious. Thanks guys!
 

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Also I’ve thought about bringing the car to a shop that specializes in auto wiring to verify all connections. If none of these other items aren’t obvious I hope it’s not a tiny electrical connection but I sort of do hope $ wise. Just may be hard to track down.
 

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.........I would like to test the fuel pressure but these cars don’t have test ports. I’ve thought about intercepting the line before regulator? .......
There are couple adaptors available to do this, one that attaches to fuel rail on engine and another that connects to fuel line where it leaves fuel filter. Since it would be needed in the interior to allow quick view when engine stalls while driving, for safety I’d think you’d want an electrical sending unit to an electrical gauge. A little more complicated the hard piped gauge under hood.

Also I’ve thought about bringing the car to a shop that specializes in auto wiring to verify all connections.
If they understand wiring for this platform that might help, but many shops are shooting in dark because of differences in the 3S platforms from many cars. If you have a multi-meter and know how to use it, there’s several people here that can guide you with testing.
 

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I ran the block leak test this morning and it didn’t show any signs of head gasket leak. I also pulled spark plug wires from coil packs and each got worse. I pulled the ECM and uploaded the pics. It looks like there’s 2 small capacitors and 2 larger capacitors. It appears like the smaller capacitor on the left has already been soldered. It looks like both the small capacitors have leakage around them. The two larger capacitors look okay, atleast the area around them. How does the ECM look to you guys? It’s on a 1995 SL. Thanks.
 

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Yeah it looks like C103 & C104 have definitely been replaced. My only concern there would be that one leg of C104 looks like solder didn’t flow out right, which might indicate a cold solder joint. Can’t say for sure since the solder ball looks larger that the trace circle and outside edges of solder ball would’ve been on board surface & sealer area not allowing it to flow out correctly. Just too much solder to say for sure, but if cold solder joint that could cause the symptoms you’re experiencing.

Can’t tell about other two capacitors they might be original because solder is smaller and flowed out correctly. Also they’re closer to board which is more like factory installation.

Unfortunately a capacitor can fail without showing external signs, looking at them will only allow you to see failures when they're bulged or burnt. Of course if leaking electrolyte that can also be seen.
 

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Yeah it looks like C103 & C104 have definitely been replaced. My only concern there would be that one leg of C104 looks like solder didn’t flow out right, which might indicate a cold solder joint. Can’t say for sure since the solder ball looks larger that the trace circle and outside edges of solder ball would’ve been on board surface & sealer area not allowing it to flow out correctly. Just too much solder to say for sure, but if cold solder joint that could cause the symptoms you’re experiencing.

Can’t tell about other two capacitors they might be original because solder is smaller and flowed out correctly. Also they’re closer to board which is more like factory installation.

Unfortunately a capacitor can fail without showing external signs, looking at them will only allow you to see failures when they're bulged or burnt. Of course if leaking electrolyte that can also be seen.
Hey guys I just want to give y’all an update on my vehicle since y’all were helping me out and helping track down my issues. I bought a used ECU for about $300 and when I installed it, it made my car shake pretty bad just at idle but did throw a code for the throttle position switch. I sent that ECU back and found one from the marketplace for around $100, put it in and everything seems to be going good so far. I’ve driven it for 2.5 weeks with no intermittent stalling. I also noticed that the EGR solenoid top hose connection was broken off and that part came in today. I’m gonna change that and keep rolling! I appreciate all your help, thanks!!
 

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......... I appreciate all your help, thanks!!
Glad to hear you may have cured your problem for now and thanks for the followup. You’re more than welcome for any help I was able to give. (y)
 
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