O2 sensors not getting hot enough or reading right. Could be. 
That could be why, either way you look at it. 
LT1 computer stuck in Open loop mode.
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LT1 computer stuck in Open loop mode. Any one have any idea why. I have aftermarket everything including the 32 lbs injectors. 355 LT1 with a serious cam .584 lft XFI
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I checked the scanner and it says that when I put it into closed loop mode manually with the scanner that my O2's are working properly and then I checked everything else. Everthing looked like it was working properly 
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Staging Lane
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I had a similar problem a while ago. No codes thrown, the computer showed closed loop, but the BLMs were locked. I logged a run with Datamaster and checked the engine bit display. It was showing an intermittent injector fault.
Staging Lane
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Originally Posted by ZEX-Z
What is an intermittent injector fault? What do you mean BLMs are locked?
The intermittent injector fault came up in Datamaster under the Engine Bit Display.
'Injector Fault Detected This Run Cycle'
It occurred on just about every run cycle on mine which caused the computer to lock the BLMs.
I'm thinking on mine that it was an injector plug that wasn't seated properly. Checked each of the injectors with a stethoscope, heard some funny noises from one, tugged on the harness and reseated the connector. That cleared up the strange noises on the injector and cleared the fault bit.
This doesn't necessarily relate to the problem you had, but it does show how the computer can have a fault code that doesn't turn on the check engine light.
So which sensor cleared the open loop problem?
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I replaced the map sensor, coolant temp and the O2 sensors. What year is your car? Did it fix the problem when you reclipped the injector back on or did it turn out to be the computer or the injectors themselves.Who might have a datamaster? How was your car running when this happened to you? Was it doing the same thing?
Staging Lane
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My car is a 94 so it's OBD1. It was running rough and the fueling was way off. I don't know if this is the same type of symptoms you are or were having.
Don't know if it was reclipping or moving the wires that fixed the problem, but it cleared it up and ran right afterwards.
Datamaster is software from TTS Power systems and works on 92-95 LT1s with OBD1. If you have a later PCM, you would have to use some other software that someone else on here could probably recommend. It also requires a cable to plug from your computer to the under dash connector.
Depending on the scan tool you used, it may not show all of the data from the PCM which was how I found my problem.
The shop you had the car dyno tuned at should have some way of scanning the PCM if they're around you.
What are the symptoms of the problem you are having? How do you know it was stuck in open loop?
Don't know if it was reclipping or moving the wires that fixed the problem, but it cleared it up and ran right afterwards.
Datamaster is software from TTS Power systems and works on 92-95 LT1s with OBD1. If you have a later PCM, you would have to use some other software that someone else on here could probably recommend. It also requires a cable to plug from your computer to the under dash connector.
Depending on the scan tool you used, it may not show all of the data from the PCM which was how I found my problem.
The shop you had the car dyno tuned at should have some way of scanning the PCM if they're around you.
What are the symptoms of the problem you are having? How do you know it was stuck in open loop?
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Well it was stuck in open loop mode but it goes into closed loop now. but the problem lingers around still with no codes. It starts very easly. Runs great until it goes into closed loop then the car freaks out and starts backfiring over 3000 rpms. I checked the plugs and i am getting lean conditions in closed loop mode. Fuel pressure is at 44 and at wot it is 45-46. I have 32lb injectors. The car has been tuned and it just started doing this one day. I think the computer is screwed up. I even put brand new O2s in after I was having this problem. What else can I do? no check engine lights or anything. I was told I am getting a lean pop. Which is a lean backfire... My idle is up as well. But when the car is in open loop it runs bad ***.?
