I bought a 1990 IROCZ 5.7 TPI w/G-92 over a year ago, and have been wating to work it into my plans since. I finally got to put it back together after it came back from the body shop. Some drivability problems have appeared that confound me:

1) Idle quality in open loop is acceptable, but deteriorates in closed loop.

2) My Snap-On scam tool says "mismatched"

3) Torque Converter lockup appears to be erratic

4) The PROM in the 7730 ECM is a Hypertec 120322

5) I have a spare 7730 ECM from a V-6 car, and I notice the PROM is much longer and fills the entire PROM area, and has a blue "carrier".

6) It used 5 gallons of gas in 63 miles

My question is; Should I get an original type PROM?

Fuel pressure regulator, and MAP sensor have been replaced.

 

es, if for nothing more than a base line.

 

Have you done a basic tune up on it? A bad O2 sensor could be causing the crummy idle in closed loop. I'd try to find an original Prom for it but the Hypertech one should run it "ok".

Look carfully at your prom that is currently in there. See if perhaps the stock blue carrier is attached to the side of the board that the Prom is attached too. The other stuff like Limp home mode are not on the prom and I can't imagine that Hypertech would eliminate them.

 

The Hypertec PROM only seems to use about one half of the PROM location on the ECM. The stock blue carrier is missing.

I am unable to read any engine data because the Snap-On scan tool cannot seem to read the info "mismatch" is all is says when I attempt to connect it. I am wondering if the Hypertec PROM is causing this?

 

You are looking in the right direction.

 

It sounds like you have something similar to the picture below. If you do, then from I can tell, you don't have a memcal hooked up on it. You need an AUJP memcal (90-92 350 auto), and you need to either use that memcal instead of the hypertech, or mount the memcal on the 90 degree pins that the hypertech has.

The car will not run right until you do one of those two options. Do not use a 305 memcal, or a V6 memcal, they won't work right either.

 

For some reason I was unable to view the attachment. My computer wants to know what program I want to use to open it?

I have the feeling I need to locate or just buy the correct GM part.

 

Just buy a stock GM 350 chip from the Dealer for about $50. That will give a base line to work from.

 

Let me try to post the pic differently....

 

Not sure why its coming up as a link instead of displaying the picture. Try opening it with Microsoft Paint, it should work fine.

 

What kind of file are you trying to attach? Nevermind, it's a jpg. The download works fine for me. I can see the pic of the Hypertech mem-cal adapter.