88blkiroc

I just finished swapping a L98 from a 92 GTA into my 91 Formula that originally had a LB9. I ordered a brand new PROM from the local Pontiac dealer and installed it. Once the engine was running the SES light came on, the IAC bypass opened up (making a really loud sucking sound), and we have no communication with our scanner (I own a ful service auto repair shop, the scanner is a Snap-On MT2500). I put the original 305 chip back in and everything run normally. No SES light, the data link works, and the IAC goes back to normal. Runs smooth as can be. So, any ideas on the problem? I called the dealer and rechecked the part number on the 350 chip, which is 16151348 and that correct. The computer's service # is 16198262. The only numbers I saw on the 305 chip were on the silver sticker inside one of the round holes on the top of it.
It says:
Delco
AXXF
3076

BTW, I changed all the sensors including the knock sensor & MAP sensor out with the correct ones for the 350, they are all Delco sensors. Any help is greatly appreciated.

JB22

Did you replace the ESC too?

I dunno if that would give you the problems your describing, but I know the ESC is different from the 305 to the 350

88blkiroc

ESC? Knock sensor?

JB22

Electronic Spark Control Module

ACDelco Part# 216-47
GM Part# 16128261

I think its $100 from the dealership

techno101

can you check to see what code its throwing? Do it the old fashioned way with a jump from A to B. Might help....

88blkiroc

There is no connection with the data link connector when the 350 chip is installed, even when u jump the terminals. I dont think the ESC is bad cause when I run the 305 chip there are no codes and everything runs fine.

techno101

Have you tried a spare ECM unit?

jonarotz

iTrader: (26)

I'm not familiar with the ECM# you listed but a 91' and 92' both used a speed density setup. I have the AXXF chip in my 91 Z28 with the LB9. The last 3 digits on my ECM are 730. If it runs fine with the AXXF chip I would say you got the wrong chip. The mamcal/chip contains the ESC for the speed density set ups so there is no need to purchase another. Does the new chip have a silver sticker on it?

88blkiroc

Yeah, the new chip says AUJP 1615 1348

jonarotz

iTrader: (26)

Intresting...that chip should work. Like I said I am not familiar with that ECM, I would try to find a 730 ecm and give that a shot.

88blkiroc

My ECM & the 730 are the same ones. Just updated service numbers.

JP86SS

iTrader: (1)

you're correct on the 262 being the updated 730. It is not the problem with AUJP memcal.
The data line may not be wired to the same pin as the new ecm.
ESC is built in on the 730 so the external unit is not used.
What ecm was in there previously?

D's89IROCZ

I did a LB9->L-98 swap . Didn't need to change the ESC . Although it was from a 1989 ( 165 ecm) I think it should work or you. What about VATS ...would it go that far as to not be able to communaciate. You sure the chip is installed correctly in the memcal? Not doubting you abilites by any means just saying the little things that could be wrong. Did you swap the Knock sensor ( it is different between 305 and 350 engines?

88blkiroc

I dont know, I just got the car this way. I never replaced the ECM.