Cold Start Auto Rev

[MechEngineer17]

Hey everyone, I finally got a quick video update of my truck doing this funky idle-up rev when it’s under 38 degrees.

Still not sure as to why or what it is doing, but it is going to about 1000rpm, then back to idle on and off.

It drives fine, and the exhaust brake cuts on and off as usual when driving or at temperatures over 40 degrees.

I attached a quick YouTube video of it in action. It’s almost as though it doesn’t want to stay in high idle.

Thanks in advance.

https://youtube.com/shorts/lnuI0zJz_...CMiOmarE6JChQQ


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[AK Bob]

Hey everyone, I finally got a quick video update of my truck doing this funky idle-up rev when it’s under 38 degrees.

Still not sure as to why or what it is doing, but it is going to about 1000rpm, then back to idle on and off.

It drives fine, and the exhaust brake cuts on and off as usual when driving or at temperatures over 40 degrees.

I attached a quick YouTube video of it in action. It’s almost as though it doesn’t want to stay in high idle.

Thanks in advance.

https://youtube.com/shorts/lnuI0zJz_...CMiOmarE6JChQQ


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Very strange; I don’t like the amount of black smoke for such a small RPM change either.

I was wondering if perhaps the diet plan is the cause.

Do you have a functioning grid heater?

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[MechEngineer17]

Very strange; I don’t like the amount of black smoke for such a small RPM change either.

I was wondering if perhaps the diet plan is the cause.

Do you have a functioning grid heater?

Yes, I currently do have a functioning grid heater.

However, I will be doing the Banks Monster RAM and the grid heater relocation tomorrow morning.

When driving and idling any other time, the truck does not smoke unless I put my foot in it, but I rarely get on it, so it hardly ever smokes.

Only when it does this weird rev does it smoke this way.


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[watersupply189]

Did you try and unplug your exhaust pressure sensor as Nelsen03 stated he did on the above post?


2016 Ram Laramie 3500, G56, 6.7, CC, 4x4

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[MechEngineer17]

Did you try and unplug your exhaust pressure sensor as Nelsen03 stated he did on the above post?


2016 Ram Laramie 3500, G56, 6.7, CC, 4x4

This morning I did not, I wanted to see if it would do it again based off of outside temp with the sensor plugged in.

I will do it again in the morning this time with the sensor unplugged.

Now that I know this only happens under a certain temperature I can hopefully repeat the results in the morning but I will unplug the sensor first and give it a shot.

I just wonder why the sensor would only cause issues when trying to high idle when it’s below 40 outside.

High idle is totally fine when it’s above 40 so I will be stumped if it solves the issue.


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[MechEngineer17]

Did you try and unplug your exhaust pressure sensor as Nelsen03 stated he did on the above post?


2016 Ram Laramie 3500, G56, 6.7, CC, 4x4

Okay so I have an update. Saturday I installed the Banks monster ram with the grid heater relocation which went well.

So after driving it Saturday night I let it sit all night unplugged the exhaust pressure sensor and tried a cold start and it did not do the mystery rev/lope.

However it was about 40 outside.

So I tried again this morning with it unplugged because it was 36 and sure enough it started doing the rev/lope after about two minutes of idling.

So it must not be the sensor. However I bought the truck already tuned with a RaceME so my best guess is that it has box tunes.

Could this maybe be a reason for this issue or more likely mechanical?


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[kgharrin]

Can you observe desired and actual fuel rail pressure during the event and report back?

I wonder if your FCA (fuel control actuator) sticks when put under a load from your exhaust brake during warmup.

This would likely happen in cold weather until the control valve warms up.

As others have mentioned, another parameter to report back with is the actual vs. desired VGT position.

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[MechEngineer17]

Can you observe desired and actual fuel rail pressure during the event and report back?

I wonder if your FCA (fuel control actuator) sticks when put under a load from your exhaust brake during warmup.

This would likely happen in cold weather until the control valve warms up.

As others have mentioned, another parameter to report back with is the actual vs. desired VGT position.

Is there an easy way to gauge the fuel rail pressure using the RaceME Ultra, or would that require me to have an MM3 system?

And also the VGT parameter I am not sure how to gauge that as well, but I can do some research.


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[MechEngineer17]

Can you observe desired and actual fuel rail pressure during the event and report back? I am curious if your FCA (fuel control actuator) is sticking when put under a load from your exhaust brake during warmup.

In cold weather this would be more likely to happen until the control valve warms up.

As others have mentioned, another parameter to report back with is actual vs desired VGT position.

Excuse my ignorance LOL it’s all pretty new to me still.

I was playing with my RaceME Ultra on lunch, and I was able to find actual rail pressure and VGT info, so tonight, I will configure a screen accordingly so I can put all the readings.

I need to come morning time tomorrow; so I can give everyone good findings and not just a basic response.

I appreciate all the help so far!


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[AK Bob]

Is there an easy way to gauge the fuel rail pressure using the RaceME Ultra, or would that require me to have an MM3 system?

And also the VGT parameter, I am not sure how to gauge that as well, but I can do some research.

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Not sure if the RaceME Ultra is the same, but with the MM3, you choose the PIDs and record a data log.

Import the captured data into Excel and plot a graph.

If you have a higher-end scan tool, you can simply pick the PID, and it will plot a graph.

See attached examples.

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