So as some of you may have read in the LT1 section, I was chasing a problem with my car running like crap and I think I found ONE of the problems...probably the biggest one. Faulty injector wiring confirmed with a noid light on cyl 7. It'll stop firing when the wire is wiggled.

When the injector doesn't fire, 02 mV shoots down to the teens. Makes perfect sense as one would assume the cylinder is shooting out a straight shot of fresh air if the injector isn't firing any fuel to cause combustion.

Here is what is confusing me. BLMs on that side are at a perfect 128 at idle...when the injector acts up and doesn't fire, or if i purposely pull the injector pigtail off, BLM's go DOWN into the low 120's. WTF! Why would the PCM be taking away fuel when 02 mV is in the teens?

 

bump

 

What do the BLMs do if you disconnect a different injector?

 

Good question, i'll try it and see (maybe even try it on bank 2 where there are no known injector problems). As soon as I can check this i'll get back to you. Thanks!

 

When it sees a huge rich swing in the AFR, It probably knows it's not running rich because it knows how much fuel was delivered, and assumes combustion did not take place. Might be a cat protect function or something?

 

You are probably on the right track. It is the opposite though. It is seeing a huge lean issue (injector stops firing, injects no fuel, cyl pushes out fresh air causing 02mV to go into the teens) and then BLM's drop below 128 so the computer starts taking AWAY fuel which only makes the lean condition worse. I think you're on the right track, I just can't reason this one out though...

My friend took his scanner back, but I can hook it up to our MT2500 at work to do what Steve9899 said.

 

You're right, I got that backwards. Low voltage is lean.