jordankeck

Guys, I need some help with my 93 Z28. I recently swapped in a 6-speed, and when I installed a 6-speed PROM, the car runs like crap at idle. Before the swap, the car did have a VERY light flutter in the idle and at lower RPM's before the PROM swap, but the car did not have the idle issues that I now have. I uploaded .uni files of an old log with the auto trans, and also one from after the T56 swap. Can anyone look over the data and help me understand what's going on?

https://docs.google.com/open?id=0B7x...2ZlaVJ6dGFPLXc
https://docs.google.com/open?id=0B7x...zYtTW4td3RSRjQ

Thanks!
Jordan

Injuneer

Since the swap, it's idling way too low. Are you sure you have the right PROM? There is no "target" idle speed shown in the data log. It is "0" so the ECM has closed down the IAC valve to "0" and I would assume the engine is idling (at 425 - 500 RPM) on whatever air can get past the closed throttle blades and the PCV system. The program appears to be incomplete. The spark advance is only 14*. I have never seen an LT1 idle that low, so I don't know if that is the normal advance pulled off the stock program table at such low RPM, or another programing problem. Stock T56 programming is 800 RPM fully warmed up.

The A4 log shows the correct 650RPM target idle speed, and the IAC valve is opening to 20 counts to hold the idle there. The spark advance is 25*, which would appear normal.

With the engine idling that low, and unable to adjust the idle speed using the IAC valve, it's going to feel a lot rougher, and RPM will be moving around a lot more.

You have a problem with fueling in both data logs. In both cases, the long term fuel corrections are down at 108 on both sides (lowest permitted in stock programming), pulling 15% of the fuel the ECM would normally supply. Have you ever addressed this problem, even before the trans swap?

The logs also show a significant different in coolant temp and inlet air temp.

4L60:
Date - 3/20/12
Coolant - 193.6*F
Inlet Air - 123.4*

T56:
Date - 5/9/12
Coolant - 163.9*
Inlet Air - 68.9*

Were the ambient conditions that much warmer in March?

jordankeck

I picked the PROM up from another forum member that told me he pulled it from a running 93 M6 car. I told him that I had issues after installing the PROM and he assured me the PROM was good. Obviously from what you are telling me, the PROM is missing key programming to operate properly! Any idea how those parameters could be missing from a stock PROM?? It sounds like I need to get a different PROM.

As for the temperature difference, we did have a REALLY warm winter. I know we had some days in the 80's and it was probably in the mid-50's when I made the log today.

I did not address the fuel issue. When I bought the car, I was told the fuel pump was bad and replaced it with an OEM equivalent. I also replaced the fuel pressure regulator and fuel filter. Any idea what my issue could be based on the data log and the details that I have given you?

Injuneer

Could be a s simple as your injectors being larger than the PROM is programmed for.

jordankeck

I just wanted to update this post that my idle issue is fixed. The 93 ECM has an ORANGE/BLACK wire running to connector A, position 21 that is for the auto Trans Position Switch. As soon as I pulled that from the ECM connector, the car idles PERFECTLY. I have not ran a data log yet but I took the car for a quick spin and the car seems to run great.

I took a look at my injectors to see if there was any text on them to identify if they are stock or not. Is there an easy way to tell what injectors I have? Mine look like the standard injectors shown on Rockauto with the metal base and plastic upper body: