Stock Chip

[whiner]

Is there any way to identify the stock GM chip in a TB?
Is there a GM part # on the chip.

 

[ijames]

There is a delco part # but I don't know what they are. There will also be 3-4 letters and 4 numbers, giving the broadcast code and maybe the checksum. Anyway, if it is CMW602 that's the 86 chip, ACXA is the late 86-all of 87 production chip, BBKJ is the emissions recall chip from 1989 or 1990. Don't remember what the 89 TTA chip was.

 

[davelostmissing]

Can anyone summarize the differences
ACXA vs BBKJ
Which is more driveable?
Dave

 

[xrunner123]

BBKJ = Recall factory chip (emissions)
ACXA= 1987 OEM factory chip

 

[dennisL]

Driveability is the same with both chips. The changes to the BBKJ chip were made for emissions and don't affect performance. One or two of the changes might improve warm-up idle slightly but the others are for closed loop learn control (BLM stuff).

None of the changes affect the ability to “melt tires”.

Dennis

 

[DavzGN]

The both versions of stock chips have too much timing for today's Fuel.

David

 

[84gnguy]

The both versions of stock chips have too much timing for today's Fuel.

David

this is true...they are good to have around to pass emissions

 

[davelostmissing]

Thanks Guys
I don't remember getting a recall notice for this?
So neither chip is good for 91-94 octane?

 

[ijames]

Some people think the emission chip does not idle as well as the original. It is a hair leaner everywhere but wot (they tweaked the O2 sensor thresholds slightly), goes closed loop at a lower engine temperature, and may start learning the blms at a lower engine temp as well. I went ahead and used the emissions chip as the base for all of my chips and have never noticed any issues. The stock chips used 21-22 deg of advance at wot (depending on coolant temp), which is a bit much for today's 93 octane pump gas at stock boost levels on a stock motor. Most tuners run 19-20 deg at wot for 93 octane these days, or just turn the boost down a little with the stock chip (oh, the stock chips also expect a 195 thermostat so the fan on/off temps are up there ).