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Jun 11, 2023 | 07:30 PM

#46

rla2005

Fleet Owner

Joined: Oct 2005

Posts: 20,789

Likes: 1,753

From: Kentucky

Already answered your question concerning Code 13. You are failing the low speed portion of the test. It is not an indication the idle RPM is low.

Jun 12, 2023 | 05:30 AM

#47

Bigredf1505.0

Thread Starter

5th Wheeling

Joined: Jun 2023

Posts: 28

Likes: 1

Quote:

Originally Posted by danr1

Back in post #34 Randy asked the result of unplug the IAC with the engine running, did not see where you post the effects of doing so.

If you have not done so yet, knowing what if any change that makes would be helpful.

Apologies if I missed it.

had no effect. Hadn't tried again since got new iac.

Jun 12, 2023 | 05:40 AM

#48

Bigredf1505.0

Thread Starter

5th Wheeling

Joined: Jun 2023

Posts: 28

Likes: 1

Quote:

Originally Posted by rla2005

Already answered your question concerning Code 13. You are failing the low speed portion of the test. It is not an indication the idle RPM is low.

am I doing the test wrong? When 8cyl comes up I do the steering wheel turn, then mash and release brake, then wait for code reader to say 10r then hit throttle. Am I supposed to wait to hit throttle or something? Is it a failure on my part or the engine/computer? If it were a sensor wouldn't it have another code or check engine light? That is what makes me think the lower intake gasket because high idle is like a vacuum leak. But I don't have anymore vacuum leaks and when I spray starting fluid around intake get nothing. Maybe the throttle body itself?? Or am I just expecting to much for the truck to idle at normal rpm in park. Do you think this would be a problem if I go ahead and start driving it?

Jun 12, 2023 | 05:54 AM

#49

Bigredf1505.0

Thread Starter

5th Wheeling

Joined: Jun 2023

Posts: 28

Likes: 1

Quote:

Originally Posted by rla2005

Code 13 KOER indicates the computer cannot control the idle RPM in the lower range during testing.

A small vacuum leak will cause no load idle RPM to be too high. Under load, in drive/reverse, the effect of the small leak is less noticeable.

How do I test for this? I repaired all visible vacuum leaks.

Jun 12, 2023 | 06:17 AM

#50

rla2005

Fleet Owner

Joined: Oct 2005

Posts: 20,789

Likes: 1,753

From: Kentucky

Quote:

Originally Posted by Bigredf1505.0

Code 13 has nothing to do with human interaction during the KOER tests. As I have stated before the computer is testing the idle RPM in an upper range and lower range. Code 13 is flagged during the lower RPM range because the computer cannot control the RPM via the IAC since the "base" idle RPM is too high.

Quote:

Originally Posted by Bigredf1505.0

If it were a sensor wouldn't it have another code or check engine light?

Your issue with the high idle is most likely not caused by a sensor...more likely you have a vacuum leak. Less likely someone has jacked with the throttle stop screw since the RPM in Drive appears to be okay.

Quote:

Originally Posted by Bigredf1505.0

That is what makes me think the lower intake gasket because high idle is like a vacuum leak.

There is also a throttlebody gasket as well as IAC gasket. The throttlebody itself can be worn at the shaft or blades which introduces unmetered air, aka vacuum leak.

Quote:

Originally Posted by Bigredf1505.0

But I don't have anymore vacuum leaks and when I spray starting fluid around intake get nothing.

Another example for not using the spray method to find a vacuum leak on an EFI vehicle with dozens of feet of covered vacuum lines and external vacuum operated mechanisms that can and will introduce unmetered air.

Quote:

Originally Posted by Bigredf1505.0

Maybe the throttle body itself??

That is also another possibility as stated above.

Quote:

Originally Posted by Bigredf1505.0

Or am I just expecting to much for the truck to idle at normal rpm in park.

It is not an unrealistic expectation for the truck to have a normal Park/Neutral idle RPM as well as in Drive.

Quote:

Originally Posted by Bigredf1505.0

Do you think this would be a problem if I go ahead and start driving it?

You could start driving the truck, but I would still work on identifying where the extra air is coming from soon.

Jun 12, 2023 | 06:18 AM

#51

toolman60

More Turbo

Joined: Apr 2018

Posts: 551

Likes: 151

From: King and Queen Virginia

Mechanics stethoscope to listen for leaks,propane torch on but not lighted to move along all possible places for vacuum leak and listen for increase in RPM, Carb cleaner spray same as propane, spray all possible areas for leak,EVAP smoke machine,King Edward Cigar blow the smoke into vacuum line. Or air compressor with regulator on it set at 2 psi and soapy water mixture. With the air compressor method you do not have to deal with running motor.

Jun 12, 2023 | 06:25 AM

#52

rla2005

Fleet Owner

Joined: Oct 2005

Posts: 20,789

Likes: 1,753

From: Kentucky

Quote:

Originally Posted by Bigredf1505.0

How do I test for this?

Process of elimination. Unplug and cap all of the vacuum lines at the vacuum tree on the upper intake manifold, as well as the one on the rear for the PCV valve, except the fuel pressure regulator and MAP sensor. Start the engine, then unplug the IAC. If the idle RPM returns to normal or the engine stalls the vacuum leak is external to the engine. If the idle RPM is still high, the vacuum leak is on the engine.

You can use a hand held vacuum pump/gauge to test each vacuum circuit. Some folks have built their own smoke machine to test for leaks. Just to verify, I would also check the the throttle stop screw to see if someone has jacked with it. Some folks think it is an idle adjustment screw. Look for signs of the blue loctite being compromised. As stated before messing with that screw also affect the idle RPM in Drive.

Quote:

Originally Posted by Bigredf1505.0

I repaired all visible vacuum leaks.

Now is the time to find the hidden ones.

Jun 12, 2023 | 06:26 AM

#53

rla2005

Fleet Owner

Joined: Oct 2005

Posts: 20,789

Likes: 1,753

From: Kentucky

Quote:

Originally Posted by Bigredf1505.0

had no effect.

Another sign you have a vacuum leak.

[/QUOTE]Hadn't tried again since got new iac.[/QUOTE]

You should test again.

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Jun 12, 2023 | 07:50 PM

#54

Bigredf1505.0

Thread Starter

5th Wheeling

Joined: Jun 2023

Posts: 28

Likes: 1

Rla2005, thank you so much. I need the truck as a only running vehicle right now and will be running it. Will update when I work out this little grimlin causing the high idle. I think you gave me all I need to work it out, and will be, as soon as I get another vehicle going for work. keep a look out for the update.