I'm trying to data log with DataMaster so I can tune my new engine and the ECM won't go into closed loop. My BLMs just sit there at 128 not changing at all. What could be causing this? Also, on a somewhat unrelated note, my engine had a cold start injector switch but I did not see a cold start injector anywhere on that intake. What is that all about?

 

Lots things could be keeping it from closed loop. Might not be getting hot enough. There are also some closed loop timers that need to time out......might also be something wrong with your bin......got any codes?

Cold start injector is a special injector on the pass side of intake, actually bolts into the runner, (i think), and has a special connector. Gets fuel from the LeftRear end rail, via small tube attached to the injector.

 

Is it like mine where you have to remove the 10k resistor after datalogging has begun or else it will keep the ecm in a weird mode - high idle, whatnot.

 

Several things can cause your car to get stuck in open loop. I had the same problem with my 1991 L98. GM dealer wouldn't look at it. My mechanic couldn't figure it out. So, I found a new mechanic. He discovered it was the fuel injectors, which are a common problem on our cars. I ordered replacements from SouthBay Fuel Injectors. Cleaned out my TPI, then had my new mechanic replace some sensors, replace the schrader (spelling?) valve, and add an adjustable fuel pressue regulator while he was at it.

 

I understand what the cold start injector is/does, but what I'm saying is that the original engine had a cold start injector switch on the front of the intake manifold, but it did not have a cold start injector. Also, the injectors I have now are from South Bay and I just installed them not long ago.

 

Many folks remove that injector, and just plug it off. Should be 1 plug where the injector goes, and a plug at the end of the left fuel rail, where that injector gets its fuel source. The cold start switch is what enables the 9th injector, depending on temp. Thus this injector is NOT ecm controlled. So for cold start enrichment, most folks just add some more crank fuel in the bin calibration.

On the other note, i find it very hard to believe that another poster had injectors preventing closed loop operation. The injectors can certainly go bad, but they are just told to open/close from the ECM. If they were all bad, your engine would not run at all.

 

I agree. Bad injectors wouldn't prevent closed loop. They're not controlling anything. They're being controlled by the ecm!