Name that ECM

[Aliasct]

So... Bought a WOT-Tech chip from Ben and am having something of a problem with the install. Laugh, I know. The ECM is located under the coolant tank in the front right quarter of the engine, right? Located it and took it out. Unfortunately, I'm seeing something different than I would have expected. I have a '93 3.1L GP.

The pictures below are what I see.




It definitely doesn't look like the ECM from this thread.

http://www.w-body.com/showthread.php/45871-WO-Tech-Chip?highlight=chip+install

Am I going crazy here?

[bszopi]

First off, welcome to the site!

Secondly, that's an OBD-1.5 ECM, so unfortunately the chip won't work. And to make things worse, those PCMs currently aren't really tunable (there is someone on here working on it though). Good news, with that PCM, it means you have a 3100 and not just a 3.1L.

[Aliasct]

Ok what the f. I thought that the 1.5 OBD was only 94-96. *growl* Guess I'll be looking at the vin number a little more closely to see what style motor it actually is. At the very least the air intake is still the old 3.1 style so I still have a restrictive intake.

I really wish I had been around when my girlfriend had the motor swapped in the car, but that was before I knew her. I guess on the bright side the tiny DIC I grabbed from a '95 will actually work.

[bszopi]

93 was the first year of the 3100 and only select vehicles received it. Oddly, I DIDN'T think the GP was one of these...

Do you have a pic of the engine? Since you say there was a motor swap, I'd be interested in seeing what is inside that thing. Posting the VIN would also be helpful in trying to sort things out.

[Aliasct]

I didn't think the GP was one of those either; I'll post the VIN on the dash. Where is the engine's VIN?

There's a lot of confusion on what happened with the engine. Engine had *something* done to it after it cracked a head (overheated). It may have been a rebuild, but may also have been a motor swap. Her family is not mechanically inclined to say the least. Now I'm just trying to figure out *why* they would have swapped the engine harness for a damn motor swap.

The air intake is definitely 3.1L though, so if a swap happened they only did the block itself.

[Aliasct]

The 8th digit in the dash VIN is "T", which means it came with the 3.1L right? Here's a quick pic of the engine bay, where you can see the top of the 3.1L intake.

[SappySE107]

Did they really wire that thing up for SFI? Correct engine, wrong PCM. That is quite interesting and I am not sure how or why they would use that computer. MPFI was never flash.

[Aliasct]

I'm going to look at the Vin on the engine, as soon as I can locate it, to verify what style engine block it is. My girlfriend said "they got something close that wasn't exactly right", so I'm hoping that there *is* a 3100 under there to justify the wiring change. I'm sad that they killed it by putting the stock intake back on though. I'll probably change it back to the OBD1 box / 3100 intake (if the engine is a 3100), but damn if I'm happy about spending more to fix their mistake.

At the very least I'm beginning to understand why they wanted so much money from her!

[bszopi]

Look on the block for a big letter. IIRC, a 3100 would be "A".

Brad via Tapatalk

[Aliasct]

Thanks Brad, I'll take a look when I get off work. Where on the block should I be looking for that letter? Radiator side? Accessory side? Throttle body side?

[bszopi]

Rear driver's side. Oddly, I just looked at the 3100 I have in the garage and it didn't have a letter, but the 3500 mocked up in the Mustang did (a "C").

[Aliasct]

Interesting development; according to my 1993 Grand Prix service manual, the California 3.1L got SFI, while the federal 3.1L got MPFI. Weird. See the pics below.
I may still convert to OBD1. Or can it be OBD1 *and* SFI? Has Ben done a chip like this...?

[Superdave]

Wow... GM sure did some weird stuff in those days. I'd love to take that engine and harness apart to see what all they did there.

the gen 3 engines were in development at this time, it could be possible that this gen 2 has some of it's goodies.


I'd personally look for a regular OBD1 engine harness and ECM, save the other stuff just in case though.

[Aliasct]

You and me both. That might be a good option, I would spend less doing that than getting the 1.5 to 1 OBD adapter and I already have a chip for it. The only difference between SFI and MPFI is the injector pulsing, right? I should be able to switch from SFI to MPFI without any big issues, I think.

[SappySE107]

It would be the injector wiring and thats about it for the SFI. Im not sure how they did the 24x sensor either for idle but converting back to the stock harness wouldn't be hard at all because it would use less sensors than it has now, not more.