In Spec.?

[termite]

At least you posted! I’m willing to bet most are similar.

I want to say my 99 with the 5.7 idled around 650 at temp. It has been parked since 2016 though due to loss of oil pressure and some rust issues that made me fail inspection.

 

[east302]

@east302 do you see where it shows the IAC Relearn?

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I have the Service Manual for the 96, but it seems like it’s an off brand version and trying to navigate through it makes my eyes boil. TIA

This is from a 98 manual, but I don’t see anything specific to that relearn procedure other than this.

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This is my 98 350, first picture in park, second in drive. Closed loop but I forgot and left the a/c and radio on.

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And this is another 98 350 from a while back. Pretty sure it was in park, but the fuel trims were bad so it’s probably not a great comparison.

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[Caman96]

This is from a 98 manual, but I don’t see anything specific to that relearn procedure other than this.

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This is my 98 350, first picture in park, second in drive. Closed loop but I forgot and left the a/c and radio on.

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And this is another 98 350 from a while back. Pretty sure it was in park, but the fuel trims were bad so it’s probably not a great comparison.

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Ok, so I’ve done both IAC and TPS sensor relearns. Picture above again confirms “Desired Idle(Commanded?) to 550. My idle was/still is 650 rpm’s @temp./in gear. Thank you @east302
Have to consider vacuum leak. Or a bad IAC, although Dash Command confirmed the PID “Engine RPM” is the commanded rpm and if that’s true, why would that be my Commanded RPM(650)?

 

[east302]

If Dash Command is reporting both commanded and actual rpm, then they look to be fairly close to each other regardless of gear selection. To me, that says that the IAC valve is adjusting correctly. Seeing the IAC counts would probably confirm that.

The valve is adjusted based on the VCM’s interpretation of, among other things, engine load. See attachment.

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Intake air (MAF) plays into how it calculates that, so unmetered air seems reasonable. Wouldn’t a vacuum leak be present at idle regardless of gear selection?

In park, does the idle change when hitting the brake?

 

[Supercharged111]

Ok, so I’ve done both IAC and TPS sensor relearns. Picture above again confirms “Desired Idle(Commanded?) to 550. My idle was/still is 650 rpm’s @temp./in gear. Thank you @east302
Have to consider vacuum leak. Or a bad IAC, although Dash Command confirmed the PID “Engine RPM” is the commanded rpm and if that’s true, why would that be my Commanded RPM(650)?

If you have an idle leak, your IAC counts would be bottomed out if it couldn't correct for it. I really think you're reaching for straws here. You're looking at other peoples' commanded RPM and selectively going for what suits your desires. Since there's clearly more than 1 right answer, the only right next step is to no **** verify what YOUR truck is commanding for idle.

 

[Caman96]

other peoples' commanded RPM

So other peoples commanded RPM for a 5.7 Vortec is different than my 5.7 Vortec? Unless your saying a 96 is different than a 98 5.7 Vortec.

verify what YOUR truck is commanding for idle.

According to Dash Command my truck is commanding 650 rpm’s as noted in previous post.

 

[Caman96]

I really think you're reaching for straws here.

Of course I’m reaching for straws here, I don’t know, that’s why I’m trying to figure it out. I’ve tried everything you’ve pointed out, like TPS and that checked out.

 

[Schurkey]

Commanded idle speed and actual idle speed are essentially the same. As long as the IAC counts are reasonable...shut the hood.

If the IAC counts are not reasonable, consider vacuum leak(s), IAC problems, or "something weird" which may take effort and enthusiasm to fix.

First Guess: the computer is happy. Don't make trouble for it.

 

[Caman96]

Since there's clearly more than 1 right answer

I’m confused by this, how does a 5.7 Vortec have more than 1 right answer to what the commanded rpm is. The manual says 550. @east302 shows his at 550. T

Commanded idle speed and actual idle speed are essentially the same. As long as the IAC counts are reasonable...shut the hood.

If the IAC counts are not reasonable, consider vacuum leak(s), IAC problems, or "something weird" which may take effort and enthusiasm to fix.

First Guess: the computer is happy. Don't make trouble for it.

ok that’s fine, this all started out as a simple question of what is the idle speed for 96 5.7 Vortec. For like 8 pages, nobody could answer that. Other than specific numbers from a manual that apparently mean nothing. Seems odd. It’s ok, I learned some stuff and all good. Seemed like a logical question, but I guess no definitive answer.

 

[L31MaxExpress]

I’m confused by this, how does a 5.7 Vortec have more than 1 right answer to what the commanded rpm is. The manual says 550. @east302 shows his at 550. T

ok that’s fine, this all started out as a simple question of what is the idle speed for 96 5.7 Vortec. For like 8 pages, nobody could answer that. Other than specific numbers from a manual that apparently mean nothing. Seems odd. It’s ok, I learned some stuff and all good. Seemed like a logical question, but I guess no definitive answer.

Could be because GM put the Vortec 350 in many applications for 10 years and GM has a tendency to tweak things. A single model year can have atleast 10-15 different calibrations. GM also often releases calibration updates for various concerns once the vehicles hit the consumers. The correct answer for the right idle speed for a Vortec is whatever the commanded idle speed displayed by the PCM. The PCMs will bump the idle speed relative to charging system voltage as well.