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1G 91 Talon TSi stalls at idle

MyTalonTSi1991

Probationary Member
18
5
Jul 12, 2019
Bloomington, Illinois
I have a full stock configuration 91 TSI FWD Automatic.
Car has been running absolutely perfect and it randomly in the last month or so has started sputtering at idle and stalling.

Most of the time it drives fine with no issues but sometimes it gets very unhappy and refuses to idle. Yesterday it stalled and had a hard time starting, had to give it part throttle to get going and the tach was kind of jumping around which it never did and it took me a good probably 5-10 minutes of this to get it to stay running and idle on its own. Got it running and proceeded to drive it back to my garage and it drove just fine. It did this a couple weeks ago, originally suspected bad gas so when the tank neared empty I put in a bottle of Lucas and fresh 93 ethanol free fuel. At that time since I had some spare parts on hand, I replaced the plugs, wires and Idle motor, idle is about 750 warm when in drive, if I turn on the AC it dips to about 600. I am kind of at a loss here.

The only "mod" on the car is a Walbro 255 fuel pump since when the original one went I had a hard time sourcing an OE spec one. Could it be my ECU? Coil? Bad plug wires? This one has me really scratching my head since this car has performed flawlessly up until this.
 
Last edited by a moderator:

MyTalonTSi1991

Probationary Member
18
5
Jul 12, 2019
Bloomington, Illinois
I have no check engine light, tach works but yesterday as I was trying to start the car it was jumping a bit. I had the turbo replaced in the spring with a low mile 13B and the O2 was replaced at that point. I was also thinking maybe the cat, but it has a new one of those too, just a universal hi-flow. Been on there for a bit and haven't had an issue until now. Supposed I could pull the ECU and open it up to see if there are blown capacitors?
 

Vegas Smith

Proven Member
4,673
2,474
Dec 2, 2002
Houston, Texas
I have no check engine light, tach works but yesterday as I was trying to start the car it was jumping a bit. I had the turbo replaced in the spring with a low mile 13B and the O2 was replaced at that point. I was also thinking maybe the cat, but it has a new one of those too, just a universal hi-flow. Been on there for a bit and haven't had an issue until now. Supposed I could pull the ECU and open it up to see if there are blown capacitors?
I would do that.
 

1990TSIAWDTALON

Moderator
8,323
4,201
Nov 14, 2013
Independence, Kansas
If you had a spare PTU, I'd try that since you mention the tach being a bit different. Check out the ECU and TCU while you are there. I think it is C106 on the TCU, that goes out (might be C110, but it is the one next to the heatsink in the TCU).
 

pauleyman

DSM Wiseman
7,016
2,006
Nov 19, 2011
oklahoma city, Oklahoma
I have no check engine light, tach works but yesterday as I was trying to start the car it was jumping a bit. I had the turbo replaced in the spring with a low mile 13B and the O2 was replaced at that point. I was also thinking maybe the cat, but it has a new one of those too, just a universal hi-flow. Been on there for a bit and haven't had an issue until now. Supposed I could pull the ECU and open it up to see if there are blown capacitors?
all good replies so far. Can you elaborate on tach jumping? That seems to be the biggest clue to the root cause. If you're talking about twitching while cranking that's normal. If it jumps a few thousand I'm gonna take a guess at ecu, transistor etc.
Pulling ecu is easy enough. If you have history on it and it's old it's highly suspect.
 

steve

DSM Wiseman
13,905
956
Feb 3, 2002
Boulder, Colorado
If the car is in fact original stock except for the fuel pump, the replacement turbo and O2, you need to have the capacitors in the ECU and the main TCU one replaced ASAP and hope that the originals haven't yet leaked and damaged the PCB.

There is not if with these, it's just when and the TCU cap usually destroys the TCU when it fails.

Also replace the metal ISC with a newer plastic version that is less likely to short a coil and burn up the ECU drivers.
 

MyTalonTSi1991

Probationary Member
18
5
Jul 12, 2019
Bloomington, Illinois
Thanks! Ill pull the ECU and take a look. When I bought the car the prior owner had put an AWD Auto TCU in it because the FWD Auto TCU was made of unobtanium. Found a couple TCU's on eBay last year that had no bad capacitors so the trans appears to be fine. I dont know anything about the ECU so ill take a look at that this week when I get over to my shop to tear into it. The tach was jumping while I tried to crank it yesterday, a couple times it jumped to maybe 2000 while trying to crank and when it did try to start and was sputtering the tach was dancing a bit. Wish I took a video!
 

MyTalonTSi1991

Probationary Member
18
5
Jul 12, 2019
Bloomington, Illinois
So true! Its bitter sweet seeing the DSM plant, the good ole days there would be thousands of cars sitting out there. Now there are just empty lots. It was in the local news that Rivian is producing production trucks....so its good to see cars being made again...sadly nothing as cool as the Eclipse/Laser/Talon is being made there :)
 

dwb

Proven Member
31
11
Sep 9, 2021
Broomfield, Colorado
The tach inconsistencies could be caused by a faulty CAS. The idle dropping when turning on the AC sounds like an ISC issue to me.

How's your wiring? I've had to replace a lot of pigtails on my 91 due to age.
 

MyTalonTSi1991

Probationary Member
18
5
Jul 12, 2019
Bloomington, Illinois
I checked for vacuum leaks, cleaned the throttle body and the car was seeming to run OK. I put the car into "economy" mode today and then I started getting the same stalling, sputtering and dancing tach. Took about 30 mins to get the car running again to get back to my place. Pulled the battery and got the ECU out.....someone has clearly been in there. ECU # is MD166262, Board says JE3318997A and there is a chip (EPROM?) M67805 on it. The bottom of the ECU casing had a tag like it was a reman as it said "Warranty void if broken" but the top does not have this....but just says NO CHIP, WORKING in yellow salvage yard marking. Now I am completely at a loss here. Capacitors look like they have been replaced, board has some burn marks under a capacitor. Does anyone know what ECU I have? When I bought the car it had an AWD TCU and I replaced it with a good FWD TCU. I have no clue at this point.
 

1990TSIAWDTALON

Moderator
8,323
4,201
Nov 14, 2013
Independence, Kansas
Per @steve back in 2006 in THIS thread.
The MD166262 ECU is used in 91 and 92 model year turbo AWD cars. It is not a 90 ECU.
Production typically switched in June from one model year the the next.

Steve
Thanks Steve, we are lucky to have you on this forum :thumb:
Marty
 

MyTalonTSi1991

Probationary Member
18
5
Jul 12, 2019
Bloomington, Illinois
Hmmmm. so Someone has already swapped out the ECU with one not for this car....could definitely be an issue perhaps? Guess I need to find a MD165529 ECU which maps to a FWD Turbo Auto.
 

1990TSIAWDTALON

Moderator
8,323
4,201
Nov 14, 2013
Independence, Kansas
I really don't think that the AWD vs FWD will effect it. The motor doesn't know what it is powering, but I just wanted you to know what exactly you have now. :)
 

steve

DSM Wiseman
13,905
956
Feb 3, 2002
Boulder, Colorado
While there is some difference between FWD and AWD 1G ECU's, the big difference is between Manual and Automatic cars due to the different turbos, injectors, and base fuel pressure. That means the fueling and timing maps are quite different.

Do you have a good picture of the ECU? The only JE3318997A PCB's I have pictures of handy from were from Non-EPROM ECUs. The typical 91+ EPROM ECU usually has a JE331B989D PCB.

The EPROM is a 27128 chip like the one labeled E943 in this picture. A MD166262 Manual AWD and the MD166260 Manual FWD will have a E931 version EPROM and a MD165529 Auto FWD will have one labeled E932

You must be logged in to view this image or video.
 
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MyTalonTSi1991

Probationary Member
18
5
Jul 12, 2019
Bloomington, Illinois
Mine definitely didn't have that chip on it so its not EPROM. I am going to go over to the local scrap yard today, they have a few DSM's there and I am going to grab a PTU out of a car there just to see. They are non turbo cars but from what I read the PTU is the same part. Figured between the ECU and the PTU that should hopefully fix the issue.
 

MyTalonTSi1991

Probationary Member
18
5
Jul 12, 2019
Bloomington, Illinois
So I was able to grab a PTU, grabbed a set of NGK blue plug wires, got everything swapped out, car started right up, ran find. Decided to grab the car this morning and drive it to work....started off fine, came to a stop sign and when I went to accelerate it hesitated and then took off. Had the vacuum system checked, no vacuum leaks. Had an electronic shop look at the ECU, its a reman and everything with that looks good. Fuel filter looks newer. I'm totally at a loss here. Could it be a fuel delivery issue? Fuel Pump? Fuel filter? Given the randomness of the issue I would think its not the cat? It has a newer high flow cat on it.
 

MyTalonTSi1991

Probationary Member
18
5
Jul 12, 2019
Bloomington, Illinois
Is this something I can just remove/replace? The car has a brand new timing belt and everything. Is this something that impacts the timing or anything? Havent owned a DSM since 2001 so I am not very familiar with some of these things.
 

dwb

Proven Member
31
11
Sep 9, 2021
Broomfield, Colorado
The CAS (Cam Angle Sensor) is the hockey puck looking sensor on the right (pass) side of the head/valve cover, just behind the thermostat housing. Yours should be a green top.
Yes, very easy to replace but requires to set the base timing after replacement.
 
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