mothballed 3000GT twin-turbo

Does anyone know someone who can tune a 1991 Mitsubishi 3000GT twin-turbo? The car has been sitting for years. We've changed wires, plugs, filters, etc. The car runs, but it won't hold an idle--falls to about 200rpm, then surges up to about 600rpm. Evens out on the highway, but the boost will peg the gauge.

Exposed metal parts have a patina of very light, white corrosion. It was in England for a while, and was shipped back to Montana. I'm assuming that the corrosion was from brief exposure to salt air. No leaks. The car and the paint are in perfect condition. Mileage is only 34K, if you can believe it. Red leather interior, pearl white exterior. Looks like new.

No idea how to tune it. I'm pretty sure the injectors need to be replaced.

Any advice, info, will be greatly appreciated.

Ronin wrote:

Does anyone know someone who can tune a 1991 Mitsubishi 3000GT twin-turbo? The car has been sitting for years. We've changed wires, plugs, filters, etc. The car runs, but it won't hold an idle--falls to about 200rpm, then surges up to about 600rpm. Evens out on the highway, but the boost will peg the gauge.

Exposed metal parts have a patina of very light, white corrosion. It was in England for a while, and was shipped back to Montana. I'm assuming that the corrosion was from brief exposure to salt air. No leaks. The car and the paint are in perfect condition. Mileage is only 34K, if you can believe it. Red leather interior, pearl white exterior. Looks like new.

No idea how to tune it. I'm pretty sure the injectors need to be replaced.

Any advice, info, will be greatly appreciated.

My advice is that it is beyond repair, and that you should give it to me for disposal, lol .

I love, absolutely love 3000gt vr4s. I've wanted one for-e-ver.

Seriously though, I'd guess that it should run fine on the stock tune unless it is heavily modded. You probably have a sensor or something out of whack. I wonder what kind of scanners are out there for a '91. Do they even have an OBD interface? I wonder if they are programmable or if you have to burn a chip.

stealth316.com if you dont know about it. There is a ton of 3si info on that site.

I'd love to play with that car though, but I'd have to dust over some very old knowlege to be really helpful.

The car is totally stock, and the owner would like to keep it that way. Personally, I'd probably try to figure out how to re-wire it so that it could maybe take a new Mitusbishi ECU. No OBD port. There's a port, but for something besides OBD. Tried the Dodge dealership, but they know less about it than we do. It's the kind of car that normally lives in dog years, and by that standard it is a very old dog indeed.

I'd love to have it myself, except that I am too tall and long legged for it. The red leather interior is perfect, and it's a gas having a separate cassette player and CD player.

Looking at the electronics, though . . . it's like trying to figure out how to play vinyl on an Ipod. 1991, man. Most people didn't even have a computer in 1991. The Internet, for most people, seemed like a fad. And the 3000GT, twin-turbo, and the Supra ruled. I was in Japan at the time, drooling over the new Skylines that had V8's.

Ronin wrote:

The car is totally stock, and the owner would like to keep it that way. Personally, I'd probably try to figure out how to re-wire it so that it could maybe take a new Mitusbishi ECU. No OBD port. There's a port, but for something besides OBD. Tried the Dodge dealership, but they know less about it than we do. It's the kind of car that normally lives in dog years, and by that standard it is a very old dog indeed.

I'd love to have it myself, except that I am too tall and long legged for it. The red leather interior is perfect, and it's a gas having a separate cassette player and CD player.

Looking at the electronics, though . . . it's like trying to figure out how to play vinyl on an Ipod. 1991, man. Most people didn't even have a computer in 1991. The Internet, for most people, seemed like a fad. And the 3000GT, twin-turbo, and the Supra ruled. I was in Japan at the time, drooling over the new Skylines that had V8's.

Well, I think I'd start with finding a chiltons or similar for it. They have pretty good troubleshooting charts in them for various conditions. Break out a multimeter and start checking sensor voltages, and resistances. I'd guess that it is going to be something like a cam / crank position sensor, ignition module / coil might be a good suspect, fuel injection system possibly. Even though old, the computer systems were still there, just not as friendly to diagnose and work on. I fought some ignition problems on my '86 Buick and let me tell you, you have to go pretty old skool to figure some of that crap out but it is still computer bits and pieces.

Yeah, we're doing all that. Unfortunately, the owner, who has money, doesn't seem to understand that troubleshooting an engine like that can take a lot of man hours. So far, all the sensors look good. The cannon plugs are clean, no corrosion, etc. There's no deterioration on any of the plastic or on any of the seals--which is a surprise. But there is no way to know, at this point, what is the composition of some of the elements in the sensors. I mean, they could look good, but still need to be replaced.

Personally, I would pull the engine and transmission, and then see what I could do about modernizing the wire harness and computer. I think it would save a lot of time and money in the long run. But I know what the owner thinks. He looks at the car, and the car looks almost brand new, the engine clean, and he thinks there can't be much wrong.

Some people just shouldn't be allowed to have performance cars, that's the long and short of it. Especially people with money who drive their performance cars like little old ladies on the way to church. The cars don't like it, and it makes me grind my teeth watching them. Yesterday, I ripped by a silver-haired guy with Alberta plates driving a new, Turbo Porche--one of the limited models. He was doing 60 in a 70, hunched forward over the steering wheel, staring straight ahead like he was driving 150 through a tight S curve.

Now, I ask you. If you were driving that car, and a little, blue Subaru Wagon with a big exhaust went ripping by you, and HONKED, what would you do? I'm pretty sure he actually slowed down.

What about just cleaning the maf?

should have ODB1 under the hood

Cleaned the MAF. Cleaned all the sensors. Other than pulling codes, the shop has no equipment that can read engine parameters. Neither does the Dodge dealership. And once the parameters are read, how can you reset or adjust parameters without putting in a dedicated chip???

Most guys who have these cars, have modified them in one way or another. Many have after-market computers. But the owner wants to keep this thing stock. I don't blame him. Its condition and low mileage makes it a very rare car.

Right now, though, it is a real pain in the ass to work on.

Wile2K' thanks for the tip on Stealth 316. It's a great site, and should be a lot of help.

Ronin wrote:

Cleaned the MAF. Cleaned all the sensors. Other than pulling codes, the shop has no equipment that can read engine parameters. Neither does the Dodge dealership. And once the parameters are read, how can you reset or adjust parameters without putting in a dedicated chip???

Most guys who have these cars, have modified them in one way or another. Many have after-market computers. But the owner wants to keep this thing stock. I don't blame him. Its condition and low mileage makes it a very rare car.

Right now, though, it is a real pain in the ass to work on.

I'm thinking that "reading the paramaters" would lead to which sensor is f'd up causing it to run crappy. How do the plugs look? Any different than the others? When it starts idling down, is that right after you start it or after it runs for a bit? When you say that it pegs the boost gauge, you mean it overboosts or do you think the gauge is faulty? Stuck wastegate or whatever system it is using for boost control?

It's over boosting. The plugs and plug wires are new, and it hasn't been driven more than maybe fifteen miles total; so a little hard to see anything with the plugs. The engine sounds good, though, and for sure when it winds up it's got plenty of power. Don't want to drive it until the fueling issues get worked out (if that's what the problem is). Over boosting has to be putting it into a lean condition; you can't hear the knock, but you can feel it.

It sounds Like you could have some corrosion in the ECU common problem with the idle control on early 90s mitsubishi ECU and I have had better luck running an MBC instead of the stock solenoids for boost control on these cars.

924g63 wrote:

It sounds Like you could have some corrosion in the ECU common problem with the idle control on early 90s mitsubishi ECU and I have had better luck running an MBC instead of the stock solenoids for boost control on these cars.

Kind of what I was thinking. The IACS (Idle Air Control Solenoid) went out in my Subaru once and those are the symptoms.

I'd also check the old rubber hoses and the rubber intake, sounds like a vacuum leak or leaky intake after the MAF. There are so many things it could be but really shouldn't take more than an hour to test the system for leaks and check the sensors and valves that pertain to idle, (IACV, 02, CTS) a volt meter should clear that up quickly.

The older wiring should be simpler than "modernizing it" no reason to fix something that isn't broken in my opinion and the older systems are much simpler. No need to add complexity.

The idle is one problem. Overboost is another. All sensors and hoses have been checked as well as possible.

idle problem and overboost sound like two problems that could share one culprit... air leaks! Wastegates are as simple of a mechanism as they get, should be able to solve that issue fairly quickly.

The things that can cause overboosting should be simple to diagnose. A turbo, a wastegate and a hose. Should be pretty simple to figure out what's not working. Obviously if there is a boost solenoid or MBC bypass those for now and ensure that the basics are working.

Solve the simpler of the two problems and see if that fixes the second one as well.

I would assume this can all be solved with a leak tester of somesort, a FSM and a multi-meter.

just my $.02

the 3.0l mitz ecu's (for some reason or other) have to re lean if the batt is dead and they sit for about 6 months. they put those exact engines in the dodge dynasty and the spirt, i had a spirit with the 3.0l that has issues like that. the over boost can be , like mentioned LEAKS more than likly.

Well, considering that a village of mice were living in the engine compartment, it's certainly possible that there is an air leak somewhere. Haven't been able to find one , though. Found some mice skeletons. I'm not sure what it's got for a boost controller or where it might be. Not sure about how a bad waste gate might affect the boost, seeing as how it is a twin turbo (if one waste gate on one turbo is broken what will that do to the overall boost?). There's only one boost gauge.

Chances are that the boost/idle problems will be resolved with new hoses and injectors. But that still doesn't solve the problem of somehow being able to pull parameters off the ECU, and then to adjust those parameters. I mean, how do you re-chip if you don't know what needs to be re-chipped???

To be honest, the big problem is that no one feels like putting in the time and energy to figure out the car well enough to re-tune it. It's a one-time-only deal. These cars are far and few between, especially around here. Unfortunately, there's no one else to send it to--not anyone close, at any rate.

b1r - TS wrote:

idle problem and overboost sound like two problems that could share one culprit... air leaks! Wastegates are as simple of a mechanism as they get, should be able to solve that issue fairly quickly.

The things that can cause overboosting should be simple to diagnose. A turbo, a wastegate and a hose. Should be pretty simple to figure out what's not working. Obviously if there is a boost solenoid or MBC bypass those for now and ensure that the basics are working.

Solve the simpler of the two problems and see if that fixes the second one as well.

I would assume this can all be solved with a leak tester of somesort, a FSM and a multi-meter.

just my $.02

+1

DoodieHead wrote:

924g63 wrote:

It sounds Like you could have some corrosion in the ECU common problem with the idle control on early 90s mitsubishi ECU and I have had better luck running an MBC instead of the stock solenoids for boost control on these cars.

Kind of what I was thinking. The IACS (Idle Air Control Solenoid) went out in my Subaru once and those are the symptoms.

Had the same problem with my 87 IROC Z camaro...

If the car is totally stock why do you want to retuned it? You just need to find what is malfunctioning to make it run bad. There are lots of ideas already mentioned to try out before worrying about changing the computer parameters. If the owner wants to keep it stock then the stock tune would probably be the best to use.

There are definitely tools out there that let you "see" all of the sensor voltages / readings. In my Buick it is a Scanmaster.

Here, peep this...

http://www.3sx.com/store/comersus_viewItemBundle.asp?idProduct=26228

Consider something like that, he could perm mount it and then all of the sensors are just a button away. It is a very nice logging tool which will show tons of information. Turbo Buick guys have been loving these things for years. I'd suggest searching for it on ebay or some 3si sites to see if you can find something similar (if 3si guys favor something different) or if they like the scanmaster, maybe find a used one.

Thanks to everyone for being so helpful. All of your suggestions are useful. At this point, it's up to the owner. He doesn't want to sell it, and he doesn't want to put any money into it.

Accustomed as I am to Subaru ECU's, and to RomRaider and ECU Flash,without a way to monitor whatever it is that the computer is trying to do, it feels like driving blind.

Ronin wrote:

Thanks to everyone for being so helpful. All of your suggestions are useful. At this point, it's up to the owner. He doesn't want to sell it, and he doesn't want to put any money into it.

Accustomed as I am to Subaru ECU's, and to RomRaider and ECU Flash,without a way to monitor whatever it is that the computer is trying to do, it feels like driving blind.

Technology has a way of making us lazy sometimes. All those scanner are is simple logic controllers. Someone has built programs to read voltages and then tell you as a user what that means in car terms. It's no harder to get a multimeter and the FSM and then you become the logic controller.

Take your car that you are familiar with and teach yourself what to look for, then move onto the car that is unknown.

I must say that if someone is paying you for your service, you should really know how wastegates work and how twin turbo cars are setup in comparision to a single turbo setup (I guess I just consider these items very basic, and necessary to work on such a car). Worst case be decent and admit to the owner you are not familiare with the applications and don't charge him for all of your time researching and learning.

If you need a hand PM me and I can stop by and help you out. Seems like it should be pretty simple to get fixed and I'd be happy to lend a hand if our schedules work. This isn't think kind of thing that a new ECU or some tuning will take care of. Do you have an air compressor at your shop? I have some leak testers I could bring over depending on the size of his piping I can also whip up a new one if I don't have the right size.

I have a boost leak tester for a TDo6 should be around the same size I dont know how well it would work for you but if you need it pm me.

Nah, I'm not a professional mechanic--at least not on cars. Once upon a time, I had three MOS in the Marines that included Avionics, Electrical, and Mechanical (helicopters). And I spent a lot of time in Japan, even wrote for a major Motorcycle magazine. My father-in-law was one of the big honchos for Mitsubishi, and himself an engineer.

So the shop that is working on the 3000GT asked me for my .02, and I thought, why not ask people on this forum. The mechs who are doing the work have covered most of the ground mentioned here, but it helps to know that we have not gotten off on tangents. Thank you again everyone. More important, a few of you have offered short cuts to people who know these cars backwards and forwards.

Basically, I am the peanut gallery looking over the shoulder of the guys who are doing the actual work--which is kind of fun . . . for me. Despite the family connection to Mistusbishi, I am not a fan of Mitsubishi stuff. I much prefer Subaru and Nissan, especially Subaru.

This 3000GT, however, is a really nice car. Clearly way ahead of its time in 1991. The guys who are working on it are two of the best mechs I've ever met in my life. They are at home with any kind of performance vehicle. But what they like to do best is to re-build American muscle with a great blend of Old Skool and state-of-the-art. My question about twin turbos was meant to be a leading question: I can't make up my mind whether or not I like a twin-turbo configuration better than a single turbo configuration. Sorry if I just sounded ignorant.

Once this thing gets on its feet, I'm sure the owner will let me post pics, and also a brief story of what it took to figure out the problems.

sound cools! sorry if I seemed rude, for some reason I thought you ran a shop, and I was having a hard time beliving that you owned a shop and had these basic questions.

Have fun working with it and post pics when it runs.

Nah. Sometimes I wished I owned a shop--but then I look at all the crap the guys have to work on in order to put food on the table and my interest wanes in a hurry. Posing obvious questions on sites like this sometimes really helps because people are always quick to ask if you've tried the obvious solutions. All too often--not only with cars--it's easy to skip the mundane in favor of the unusual--more out of boredom than anything else. "Keep it simple, stoopid" is a phrase all to easy to forget, especially when it comes to the science behind these cars.