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Chevrolet Express
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High Idle

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Old Mar 11, 2024 | 7:10 AM
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Default High Idle

1992 G30, high idle, replaced the idle control valve, was running better.
Now when I drop into gear it stalls, like it’s getting no gas.
Then hard to restart.

New throttle body time?

Thanks!
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Old Mar 11, 2024 | 9:32 PM
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I'm guessing 5.7l?

You can make your own cable for the scan tool... I might have thrown out the one I made way back when.

https://charm.li/Chevy%20Truck/1992/.../Idle%20Speed/
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Old Mar 11, 2024 | 9:33 PM
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WinALDL - 160 baud ALDL reader
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Old Mar 12, 2024 | 11:02 AM
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Default Thanks!

Tried a code reader says no issues
Yes it’s a 5.7.

Last edited by Brownie289; Mar 12, 2024 at 11:06 AM.
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Old Mar 12, 2024 | 10:38 PM
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You aren't looking for a code. You need a scan tool that can look at the IAC count. There are lots of options for OBD2 but with pre-OBD2 ALDL you're looking at either expensive or DIY. I provided the DIY cheap version. Just need a serial to USB cable, the program, and a DIY cable made from some parts from "radio shack". Good luck finding a local electronics store.
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Old Mar 13, 2024 | 7:40 PM
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Yes thank you I used a scan tool. Count was 1 - 2. Meaning ok.

I did disconnect the battery after too, supposed to clear the ECM.?
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Old Mar 13, 2024 | 7:48 PM
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The only thing I have done to it was change the idle control valve…
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Old Mar 14, 2024 | 12:44 AM
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Originally Posted by Brownie289
Yes thank you I used a scan tool. Count was 1 - 2. Meaning ok.

I did disconnect the battery after too, supposed to clear the ECM.?
1-2 is too low isn't it? Charm says 5-30. Do you have a vacuum leak? Bad PCC?
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Old Mar 14, 2024 | 6:03 AM
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I haven’t really focused on a vacuum leak, just because this came on suddenly after I changed the idle control valve, actually it ran better after I changed the valve, took it for a ride performed well. A few days later this problem developed.

The book that came with the reader said a flash of 1 then 2 meant no issues.
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Old Mar 14, 2024 | 2:32 PM
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Code 12 indicates the computer's self-diagnostic system is functioning properly.

It does not indicate "no issues", since you will still see code 12 along with other trouble codes.

Last edited by mountainmanjoe; Mar 14, 2024 at 2:34 PM.
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