Idle is working, Knock on deceleration

[willn]

So, I was finally able to get the idle hammered out and the truck will go into gear and not die.

The next issue I am having is that whenever I rev the RPMs to about 2K or higher and then when it drops back down, it will drop too low and then stall. This also happens when I am going around corners and the RPMs drop.

The second issue is that when I let off the throttle and the RPMs drop, I am getting knock. So, basically on deceleration. It is shown in the log on frame 702.

My initial thoughts are the engine compensation needs to be increased, but as you can see in the tune, I have increased this way above any values I see in other tunes for similar mods.

Any ideas?

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[joecar]

Hi willn,

You attachments are not working... see post #2 here, go from step 5 onwards: Hosting-an-Image (https://forum.efilive.com/showthread.php?3064-Hosting-an-Image&p=38410&viewfull=1#post38410)

[joecar]

Knock on decel is strange... have you checked that exhaust is not hitting someplace...?

[willn]

Sorry, they are fixed. It was because of me posting and then my session timed out.

Exhaust is solid. Nothing loose at all. It is loud, however. Could it just be that the vibration from the loud exhaust?

:confused: :confused: :confused:

[joecar]

No, not vibration... knock has a very narrow frequency range, this is what the knock sensors and PCM are tuned to.

[willn]

So, I think I might have possibly figured out the stalling issue somewhat. I added more timing in the {B5932} Base spark in gear, and the stalling only happened once.

I would like to cure it completely, so my next two thoughts are to adjust the {B4338} Engine Compensation to see if maybe that will help more.

The knock issue is still there though and hasn't changed. It only happens when I hit the throttle and then let it go to 0%.

New logs below. In the first part of the log, I was getting some pretty good knock. I am confused as to what that could be. Any ideas?

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[joecar]

I'll take a closer look at your files today...

[willn]

Is there any way to tell if the IAC is bad or if it is working correctly? I am not sure what to look for in the steps, i.e. should it be at X amount of steps at a certain RPM?

Also, if I needed a crank relearn, would it throw codes?

[joecar]

At idle, IAC steps should be somewhere between 30 and 60.

You can command IAC steps from the scantool to see if it responds (idle speed changes).

[willn]

Wow, I never see that low. Mine are always above 100. I bought a new IAC, so I am about to try that.

[willn]

So I took a log and compared the Desired airflow GM_IACDES_B and compared it with the Calculated Air Flow Rate GM_DYNAIR and they were way different.

Should these be the same? Does this mean that the VE table is off or I need to add more air to the desired airflow table?

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