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400 SBC TBI tweak

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Old Mar 21, 2017 | 09:32 PM
  #51  
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Re: 400 SBC TBI tweak

Thanks for bearing with me, epic fail on my part. In my defense...who the heck makes 2 white wires power/ground and black the sending wire??? lol
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Old Mar 22, 2017 | 02:24 AM
  #52  
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Re: 400 SBC TBI tweak

I do see the green box but I don't know what color wire you need to tap without seeing a schematic.
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Old Mar 22, 2017 | 06:57 AM
  #53  
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Re: 400 SBC TBI tweak

Originally Posted by Mark Uptergrove
Thanks for bearing with me, epic fail on my part. In my defense...who the heck makes 2 white wires power/ground and black the sending wire??? lol
Because the O2 heater has no polarity, the wires can be connected to power & ground either way. Although the black wire should have been purple, as that is the color GM uses the EFI harness for the O2 signal.

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Old Mar 25, 2017 | 02:30 PM
  #54  
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Re: 400 SBC TBI tweak

Another tip that shows you are running off a correct .bin is key on engine off you should see a blink of the CE light then solld on. No blink says you are not running off the .bin.
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Old Apr 9, 2017 | 04:16 PM
  #55  
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Re: 400 SBC TBI tweak

Good info. Well, I still have something off. I can run the original al 24 pin chip (has the 400.bin on it). But when I go through the process of setting the chip type (512) erase successful, select bin, write, then verify- when I put that chip in the ecm it runs in I guess limp mode fast flashing service engine soon...crappy. what's odd is when I read the 28 pin chip it reads the same as when I read my original 24 pin (that has the 400.bin ) any thoughts?

Last edited by Mark Uptergrove; Apr 9, 2017 at 04:21 PM.
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Old Apr 11, 2017 | 12:29 PM
  #56  
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Re: 400 SBC TBI tweak

I'm back in the saddle, got my issue resolved, do any of these need tweaking? I have a new 195F thermostat in it, ill have some log data shortly.
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Old Apr 11, 2017 | 02:46 PM
  #57  
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Re: 400 SBC TBI tweak

The mv settings look normal
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Old Apr 12, 2017 | 08:45 AM
  #58  
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Re: 400 SBC TBI tweak

Your BPC is 156? What size injectors at what fuel pressure?
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Old Apr 12, 2017 | 01:32 PM
  #59  
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Re: 400 SBC TBI tweak

350 Injectors. Fuel pump is rated at 70psi but obviously it is regulated at the TBI
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Old Apr 14, 2017 | 08:35 AM
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Re: 400 SBC TBI tweak

What fuel pressure? Are you using stock spring? If so you may want to buy I a spring next step stronger from "top down solutions".
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Old May 1, 2017 | 01:53 PM
  #61  
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Re: 400 SBC TBI tweak

Greetings again. I am at my wit's end. I have verified grounding, the purple wire back to the ecm, replaced the O2 sensor, and I still do not get any readings on the O2 while logging. DC voltage from the purple wire to the ecm is a constant 1.4V. could this be a ECM issue or is it possible that something is wrong in the programming disabling the O2? thanks guys
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Old May 1, 2017 | 02:23 PM
  #62  
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Re: 400 SBC TBI tweak

Is there anything in the bin that would set the ecm for open loop only operation?
Attached Files
File Type: bin
AMUR 42.BIN (4.0 KB, 7 views)
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Old May 1, 2017 | 04:13 PM
  #63  
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Re: 400 SBC TBI tweak

Check the tan wire to ECM pin D6, it is the O2 input ground. Without it there won't be a valid reading.

> and I still do not get any readings on the O2 while logging

What voltage is the ALDL reporting? If the sensor it dead or unplugged it should report about 450 mV. That is the default setting.

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Old May 1, 2017 | 04:19 PM
  #64  
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Re: 400 SBC TBI tweak

I am on o2 sensor #2, so hopefully it is the tan ground. I know the ecm is grounded, I'll trace the tan wire out. Crossing fingers this is driving me nuts.
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Old May 1, 2017 | 07:16 PM
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Re: 400 SBC TBI tweak

Originally Posted by RBob
Check the tan wire to ECM pin D6, it is the O2 input ground. Without it there won't be a valid reading.

> and I still do not get any readings on the O2 while logging

What voltage is the ALDL reporting? If the sensor it dead or unplugged it should report about 450 mV. That is the default setting.

RBob.
457mv flat lined when engine is warm
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Old May 1, 2017 | 07:20 PM
  #66  
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Re: 400 SBC TBI tweak

Bingo..d6 is open...I cannot for the life of me find or trace out the end of this solid tan wire under the hood any places to check or...do I jus cut it and ground it?
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Old May 1, 2017 | 08:08 PM
  #67  
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Re: 400 SBC TBI tweak

Originally Posted by Mark Uptergrove
Bingo..d6 is open...I cannot for the life of me find or trace out the end of this solid tan wire under the hood any places to check or...do I jus cut it and ground it?
Most likely at the back of the passenger side cylinder head (between head and firewall). Some 3rd gens also had EFI system grounds on the back of the drivers side cylinder head.

RBob.
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Old May 2, 2017 | 12:00 AM
  #68  
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Re: 400 SBC TBI tweak

After o2 grounding.
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o2ground.zip (8.5 KB, 5 views)
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Old May 2, 2017 | 09:07 PM
  #69  
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Re: 400 SBC TBI tweak

Thanks for all the input guys. The tan wire went to never never land apparently so when I grounded it bam closed loop. I do have a question about putting a heated O2 back on. Will I be good grounding the 02 Sensor to the frame or do I have to run its ground to the D6 on the ECM? (which is now grounded and working with a single wire o2)
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Old May 2, 2017 | 09:42 PM
  #70  
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Re: 400 SBC TBI tweak

With a three or four wire heated O2 sensor, the heater ground goes to the engine block (not the ECM).

RBob.
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