87TTops

Just finished tuning the beast, and I am confused. I got startling backfire and crappy idle until I advanced all the way to what I guess is 24*. Now she runs great. This number is absurd, as I understand.

I have no idea what's in this motor. The kid I bought it from didn't seem to know what he was talking about. There was an alleged rebuild a few thousand miles ago. TPI is stock, fuel system is stock, heads are stock. Has headers. Sure feels like there's a bigger than stock cam in there, but I wouldn't know how to be sure. Those are the only two upgrades unless you count msd wires and smog and ac delete. Would a cam alone warrant PROM tuning? I just can't imagine why she would want so much initial advance.

Or is it possible something was put in wrong? Could the pulley be lying?

87TTops

OR...could there be a totally inappropriate chip in there? I don't even know where the ECM is mounted, but I'll look into getting equipment to read it.

RBob

iTrader: (1)

ECM is located under the passenger side of the dash. Stock is a silver aluminum box, although a reman may be painted black. Should have the service number 1227165 on it, although, again, if a reman could have a different number.

Get the three or four letter code off of the MEMCAL. See the sticky's on the DFI & ECM board here at TGO for pictures of that.

As for the 24* initial, is that BTDC or ATDC?

RBob.

87TTops

BTDC
Bingo! Reman ECM. Though I'm not seeing the MEMCAL. Perhaps it's under this removable plate...

87TTops

Now to find out what this means. And how to change it.
In case you can't quite read it: Delco ACXT 1099. The sticker says "Calibration Code: 0301MG" if that means anything.
Also, it says "Number: 7-7165." I'm going to assume this identifies it as a "165" for short?
According to other posts, this is the correct computer for this car. Does that rule it out as the source of my seemingly outrageous timing?

Six_Shooter

iTrader: (2)

ACXT comes up a 1987 5.0L Auto, 1227165.

How are you meansuring this 24* initial advance?

Using a timing light? Bypass wire disconnected?

87TTops

Yes and yes. It's currently set about the length of the tab behind the tab. When I started the timing session, it was so far back I could barely see it. Probably at about 11 o'clock.

xch3no2

Balancer/timing cover tab mis-match?

87TTops

That's what I was thinking at first, since the car has had some hack work done on it before I got it. But no, the real solution was much simpler than this. I've been playing with Camaros since 2003 when I got my license, and apparently I've been unplugging the EGR to set my timing this whole time. Suddenly the world makes sense, and I am pretty thoroughly embarrassed. Well at least I learned some things about my ECM today.

Since the thread is already here now, what else can I deduce from the numbers on my computer? What does the calibration code mean? Has it been modified already or just replaced, since it does say remanufactured.
Oh also, my scanner says the PROM ID is 801. Stock?