General Is my ECU tuned?

[eddyspaghetti]

Hello, I have a 1997 Mitsubishi eclipse GSX automatic that won't pass smog.
I bought it in 2016 and never was able to pass smog so I had to do it the other way. Its really been a headache. It was mostly stock other than a Turbo Xs manual boost controller, cold air intake with map, boost gauge, air fuel ratio gauges with the O2 sensor NOT connected and 550cc RC fuel injectors...

things that I added last year (2025) just to be more drivable from when I just purchased the car:

T28 turbo

Evo 3 intercooler

Intercooler piping

FP ported headers

Megan racing Downpipe

Walbro 190 fuel pump

BFG dual Port BOV

I added these just to be more drivable, I don't think these are extreme modifications (remember, my GSX wasn't able to pass smog when I bought the car in 2016 almost a decade after before I added these mods.) I have all stock parts still so I am able to install these parts again if I get the ECU problem diagnosed and able to get the car snogged.

The reason I mention this is i have a big feeling the car was modded and then when sold to me they took the mods out and they left the tune installed in the ECU. I had a GS-T a long time ago that was also stock but was significantly faster than my GSX which doesn't make sense

This GSX almost drives like there was big mods and it's trying to accelerate as if they're still there.
When I took the car to go pass smog the mechanic said the lights that were flashing didn't make sense and were all over the place.

My tags expired last week and this is my only car, I don't have a tuner also. I thought of a few things I could do like maybe buy another completely stock ECU? Or I did see listings on eBay for ECU testing and repair? I'm not sure how to go about this the best way, honestly all I want is my ECU back to factory settings.

Well, any help/advice would REEEAALLY be appreciated, thank you

 

[19Eclipse90]

First step would be to remove the ECU, open it up, and snap and share some photos of the board which accomplishes two things:
1) verify it is an ECU that can be tuned
2) gives us a look at the condition of the board

Most ECU repairs are best handled by ECMTuning. But let’s figure out what current state is before jumping to that.

 

[pauleyman]

Biggest clue is you state you have 650cc injectors presently? That's not even possible with a stock ECU. The car won't run. If that is true there has to be something to compensate. Post some pics of the car and underhood. You may have more mods than you think.

 

[eddyspaghetti]

Thank you guys so much, I'm going to do that today and will post asap, hopefully we can get to the bottom of this issue

 

[99dsmer4g63]

That's not even possible with a stock ECU. The car won't run

FWIW it is possible to run 650’s with no tune. I ran 850’s in my car and drove it to the tuner on a stock black box. Didn’t beat on it and babied it there. I didn’t really notice a difference even though it obviously was pig rich.

-Daniel

 

[danl]

FWIW it is possible to run 650’s with no tune. I ran 850’s in my car and drove it to the tuner on a stock black box. Didn’t beat on it and babied it there. I didn’t really notice a difference even though it obviously was pig rich.

-Daniel

do you think it would pass smog like that?

 

[eddyspaghetti]

Hey fellas, I got stuck doing errands all day. I'll have photos tonight or tomorrow morning, just wanted to make sure, the ECU is located under the dash on the passenger-ish side?

I'll definitely look up the location, just wanted to make sure, photos coming soon, thank y'all in advance again

 

[99dsmer4g63]

do you think it would pass smog like that?

I’d assume not running as rich as it would be. The OP does complain about the car running “sluggish” though so could be 650’s on a stock ecu .

FWIW I drove the car 10 miles and was then tuned at the shop.

OP take off both side panels on the center console. It’s tucked up front under the dash. 2 10mm’s on the left and one on the right. 4 plugs on the left. Watch the hvac rod when pulling it out. You can rip it off pretty easily.

-Daniel

 

[pauleyman]

FWIW it is possible to run 650’s with no tune. I ran 850’s in my car and drove it to the tuner on a stock black box. Didn’t beat on it and babied it there. I didn’t really notice a difference even though it obviously was pig rich.

-Daniel

A mild exaggeration. 45% more fuel is a lot. In your case I am surprised it ran at all.

 

[eddyspaghetti]

I’d assume not running as rich as it would be. The OP does complain about the car running “sluggish” though so could be 650’s on a stock ecu .

FWIW I drove the car 10 miles and was then tuned at the shop.

OP take off both side panels on the center console. It’s tucked up front under the dash. 2 10mm’s on the left and one on the right. 4 plugs on the left. Watch the hvac rod when pulling it out. You can rip it off pretty easily.

-Daniel

Thank you Daniel will do this soon

 

[eddyspaghetti]

So this is where I am so far, I removed two 10mm bolts in the front, looking around for more bolts to take out, I'm not sure if there is a difference between manual vs automatic transmission, I do have auto

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[eddyspaghetti]

So this is where I am so far, I removed two 10mm bolts in the front, looking around for more bolts to take out, I'm not sure if there is a difference between manual vs automatic transmission, I do have auto

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Just noticed that is the TCU not my ECU durrrrr I'll post in a bit

 

[eddyspaghetti]

So managed to get the ECU out things I noticed:
-2 bolts in the left were completely loose
Seems to have had clear tape from some warranty I assume, it was sliced open, like if previous owner opened the ECU

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[pauleyman]

I thought you said this car is stock?

 

[eddyspaghetti]

I thought you said this car is stock?

I forgot to add that when I purchased the car it was stock, things that I added were last year:
T28 turbo
Evo 3 intercooler
Intercooler piping
FP headers
Megan racing Downpipe
Walbro 190 fuel pump
BFG dual Port BOV

Just to help it get going, it really ran sluggish, still does but runs better

Things the car came with in 2016 (could not pass smog since purchasing it)

Turbo Xs manual boost controller
Cold air intake
RC 550 fuel injectors
Boost gauge

Air fuel ratio gauge( was never connected)

I added these mods but these are nothing TOO crazy. Car could never pass smog regardless

Y'all notice anything funny with my ECU?
Let me know if you guys need more photos or information, thank y'all in advance

 

[19Eclipse90]

It is an EPROM - so, tunable - with an aftermarket chip that, if its label is accurate, should be using the 550cc injectors. I’m no expert, but I don’t see anything abnormal on the board.

The wiring to the ECU, all the unconnected red wires, could be a problem. I assume that three go to the ECU and three go somewhere. You need to determine which three go to the ECU and exactly which pins they lead to. When you figure that out, cross reference those pin numbers with an ECU pinout to learn the functionality. That narrows down where you need to look for the other three wires. Then, use the diagrams to determine the destinations for the remaining red wires. You’ll identify those by checking continuity across them, which should allow you to then up with the appropriate red wires going to the ECU connectors.

 

[eddyspaghetti]

Biggest clue is you state you have 650cc injectors presently? That's not even possible with a stock ECU. The car won't run. If that is true there has to be something to compensate. Post some pics of the car and underhood. You may have more mods than you think.

I'm sorry, I meant to put "550cc RC fuel injectors"

It is an EPROM - so, tunable - with an aftermarket chip that, if its label is accurate, should be using the 550cc injectors. I’m no expert, but I don’t see anything abnormal on the board.

The wiring to the ECU, all the unconnected red wires, could be a problem. I assume that three go to the ECU and three go somewhere. You need to determine which three go to the ECU and exactly which pins they lead to. When you figure that out, cross reference those pin numbers with an ECU pinout to learn the functionality. Then, use the diagrams to determine the destinations for the remaining red wires. You’ll identify those and be able to match them up with the red wires going to the ECU connectors.

Ok I'm gonna go ahead and start off slow with what you said, this IS my 1st time doing this

I also wanted some advice, so I have a eprom and it seems pretty clear that it's tuned.
I just want to go back to factory settings, so I could smog the car. would the quickest way to do that would be just buying a stock 97 eclipse GSX automatic ECU? I do have OEM fuel injectors from GST, I think 450cc is the fuel injectors it comes with from factory, no?
Any advice to get this car smogged the quickest and easiest way would be appreciated, thank yall

 

[19Eclipse90]

Ask questions if you’re unsure. First thing is first, if you mean to begin venturing through the wiring, disconnect the battery before you start.

There’s no guarantee that switching to a stock ECU and stock injectors gets you to pass smog. Without knowing what exactly is on the chip on your current ECU, however, a stock ECU and injectors could give you a better chance.

 

[steve]

Do you have any idea how it's failing smog? That would help point in a direction as to what needs to be addressed.

 

[eddyspaghetti]

Ask questions if you’re unsure. First thing is first, if you mean to begin venturing through the wiring, disconnect the battery before you start.

There’s no guarantee that switching to a stock ECU and stock injectors gets you to pass smog. Without knowing what exactly is on the chip on your current ECU, however, a stock ECU and injectors could give you a better chance.

Thank you man. Sometimes I do get a lil nervous asking questions haha but I will for sure
Before removing the ECU, I disconnected the battery, I read that on one of the forums here.

If I wanted to know exactly what was done to my ECU, is there a place I could possibly send it? Someone reliable, who I could explain my situation too?

Do you have any idea how it's failing smog? That would help point in a direction as to what needs to be addressed.

I'm not exactly sure Steve. But I'm just curious, would it pass smog with a Walbro 190 fuel pump?

 

[steve]

It should pass with all these mods if they were working correctly and tuned correctly. Now passing the visual inspection, not so much.

It's the job of the fuel pressure regulator to maintain a constant pressure across the injector so that they deliver a consistent amount of fuel regardless of the manifold pressure and fuel pump output. The stock FPR has issues with larger pumps because it can't send enough volume back to the tank to fuel pressure rising under low load with a bigger pump. That's usually not an issue until you have a 255lph or bigger pump. The next bottleneck is the return plumbing in the tank with much larger pumps not flowing enough.

That look like one of the DSMChips that Keydiver used to make. It looks to have modified fuel and timing maps and I can't say how well they will smog.