C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

TECH 1 GURUS....HELP!

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Old Mar 30, 2004 | 03:40 AM
  #1  
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Default TECH 1 GURUS....HELP!

No idle at start up...slowly improves on warmup to about 650.

Here are some numbers from my tech1
engine off: throttle 0%-.60volts 100%-4.06 volts (max)
L/R 02 both 453
0 RPM-4 degrees advance (when it was running this went to about 24)
L/R pulse width 23.2 mSEC
IAC 145 Learned 32

I'm not sure what any of this means (except timing advance)...but it appears my TPS is working ok....how about the rest?...or is there some numbers I can get for you to help me diagnose this problem.

Car used to idle up on start up til it warmed up...then settle down to a good idle. I've cleaned the TB and IAC. Think my IAC is shot? Also, I get a bit of pop on returning back to idle after reving a bit. :confused: :banghead:
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Old Mar 30, 2004 | 06:38 AM
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Default Re: TECH 1 GURUS....HELP! (emoshn)

The Tech-1 is bi-directional -- that means, along with reading parameters, it can send commands to various components.
The Tech-1 can send a command to the IAC to tell it to increase or decrease the idle speed. If you tell the Tech-1 to increase idle speed and it does, then you know the Tech-1 is controlling the idle speed by moving the IAC. This tells you the IAC is working. If the idle doesn't change when you command it through the Tech-1, you need to find out why.

Tom Piper
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Old Mar 30, 2004 | 12:09 PM
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Default Re: TECH 1 GURUS....HELP! (Tom Piper)

The Tech1 will not increase the idle. I've tried that. I know I can set the idle up or down when in the IAC adjust mode...but very little happens. It appears to want to but as soon as I exit that test, it goes back to the idle it was at. Does that mean my IAC is bad?
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Old Mar 30, 2004 | 04:26 PM
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Default Re: TECH 1 GURUS....HELP! (emoshn)

I'm not sure why your IAC is at 145counts but it should be around 20counts.

You might pull the IAC and clean it & the bore and clean the TB.

Also check for a vacuum leak.
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Old Mar 30, 2004 | 04:39 PM
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Default Re: TECH 1 GURUS....HELP! (65Z01)

The IAC count is with the engine off. How does one adjust the IAC count...it was doing this before I cleaned it and TB, checked connections, checked for vaccuum leaks. Does it have anything to do with Block Learn. Seems like I read somewhere that I have to activate Block Learn and drive the car to get it to reset?

I have no codes in either the ECM or CCM.

I just went out to the garage and started it again. Ran Fine. Just like it supposed to!!!!

Must be an intermittent problem. Guess I'll buy a new IAC and connector and replace it or have it on hand if it starts acting up again. Oxygen sensor too. Does the 92 have one or two oxygen sensors?

When it comes to the TECH1...guess I'm gonna have to learn by guess and by damn. :)
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Old Mar 30, 2004 | 04:57 PM
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Default Re: TECH 1 GURUS....HELP! (emoshn)

The 92 has two, one wire .....O2 sensors.
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Old Mar 30, 2004 | 05:19 PM
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Default Re: TECH 1 GURUS....HELP! (ittlfly)

Thanks . Do you know how to test them with a TECH1 to see if they are functioning properly? Is there a code that will set if they aren't?
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Old Mar 30, 2004 | 07:16 PM
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Default Re: TECH 1 GURUS....HELP! (emoshn)

Never having the $ to afford a TECH-1, I can't says as how to check the O2's with it. If you can access their input to the ECM, the mv should be "swinging" across 450mv. .....spending as much time below as above that number. Also, if the O2's are spending to much time on one side of the 450mv, the BLM's will be above or below 128 depending on the A/F ratio that the O2's are seeing. Hope that makes sense.
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Old Mar 30, 2004 | 07:53 PM
  #9  
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Default Re: TECH 1 GURUS....HELP! (ittlfly)

It shows the 128 figure...without running. so that would be the history. BLM is BLOCK LEARN MODULE?
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Old Mar 30, 2004 | 09:22 PM
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Default Re: TECH 1 GURUS....HELP! (emoshn)

It shows the 128 figure...without running. so that would be the history. BLM is BLOCK LEARN MODULE?
As I recall (shooting from the hip here..books in the garage) ...the BLM's = block learn module.....are long term memory and stored in the ECM until the current is removed. (disconnected battery) .... there are 16 or 17 cells comprising the matrix. As the car accelarates, the ECM accesses each cell for fuel trim. The trim is stored as a direct result of the short term intergrator movement. If the intergrator(s) spend to much time on one side of 128, the long term is changed in THAT CELL.
So to answer your question, if the car is off you are looking at the long term stored memory;BLM in THAT cell.
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