Throttle stuttering on acceleration

[03'Darin]

Hey Darin, thanks for all the research. I was firmly in the camp of "my truck doesn't do this" but I wasn't reading your posts closely enough.

I basically always take long offramps/hills/etc at higher RPMs/high throttle.

If I do the 30-40% load (e.g. keep truck in gear) and accelerate up a hill, mine does it, too. It feels like older vehicles I've driven with a modified stall converter kind of deal. Not quite sure which gear it should be it, but not lockedup. I don't think you're crazy, I think the trans&ecu aren't communicating as clearly as they could be. I suggest folks try this recipe if they're curious:

1.) find an uphill grade (merge lane worked well for me)
2.) roll into it from ~20mph but keep throttle ~30-50% til you're up to 4th gear
3.) once you get to 5th, reduce throttle just enough to keep accelerating, but not enough to shift out of 5th

We've confirmed through data logging that it's not a torque converter issue.

The PCM is commanding the throttle body to make abrupt changes which is causing the feeling of an engine miss.

The PCM takes all of the output data from the engine and transmission and then processes it through multiple tables to determine the most aggressive fuel and timing it can apply. I don't know this for sure but heard there are somewhere around 100 of those tables. The PCM can pull from one table or mix and match from multiple tables. The data it takes from there is used to determine all of the power application signals. This controls multiple areas Fuel / timing / torque convert lock up / percentage of torque converter slip and so on. This is how the PCM maximizes power based engine temp, intake air temp, humidity, fuel octane and so on. So the PCM is possibly smarter than the programmers or the programmers are smarter than the PCM.

I thought about something else that may be related to this also. When I have my dash message center set on the instant MPG graph display it will frequently jump up and down very quickly. I've also seen several other people post that their trucks have done the same thing. I'm curious if when the MPG calculations are being processed that the inputs are sampled so quickly that it's detecting the abrupt throttle body movement causing the display to fluctuate very rapidly??

 

[smurfslayer]

Really interesting. It sounds like the computers are making too many and too severe throttle inputs based on steady throttle under certain load conditions. On paper, it probably looks nifty, but in practice the checks and adjustments are occurring so fast and in sufficient percentage as to create the perception of a miss.

 

[jdubub]

We've confirmed through data logging that it's not a torque converter issue.

The PCM is commanding the throttle body to make abrupt changes which is causing the feeling of an engine miss.

The PCM takes all of the output data from the engine and transmission and then processes it through multiple tables to determine the most aggressive fuel and timing it can apply. I don't know this for sure but heard there are somewhere around 100 of those tables. The PCM can pull from one table or mix and match from multiple tables. The data it takes from there is used to determine all of the power application signals. This controls multiple areas Fuel / timing / torque convert lock up / percentage of torque converter slip and so on. This is how the PCM maximizes power based engine temp, intake air temp, humidity, fuel octane and so on. So the PCM is possibly smarter than the programmers or the programmers are smarter than the PCM.

I thought about something else that may be related to this also. When I have my dash message center set on the instant MPG graph display it will frequently jump up and down very quickly. I've also seen several other people post that their trucks have done the same thing. I'm curious if when the MPG calculations are being processed that the inputs are sampled so quickly that it's detecting the abrupt throttle body movement causing the display to fluctuate very rapidly??

Interesting. I have noticed the instant MPG flutter as well, but it is hit or miss. I haven't checked it out in a while due to not wanting the reminder in front of me of my MPG's. I also do not have the miss feel at all.

Technology is great, but only when it works properly. Apparently all of these sweet computers/modules are not always working properly.

I hope they find a solution for anyone with this problem/annoyance.

 

[FORZDA 1]

@03’Darin,
Do you have a data log you could share? The ETC is used to keep the Commanded and Actual Load/Torque stabilized within compare tables and below limits. I’m guessing that the ECU sees one of the limits or there is a single cell or two in the compare tables that aren’t matching close enough and the ETC is commanded to try and meet “bad” data or possibly the ETC itself has a problem when trying to hold position in a very specific, tiny range and it is oscillating. Actual recorded data is the answer source though.

 

[03'Darin]

@03’Darin,
Do you have a data log you could share? The ETC is used to keep the Commanded and Actual Load/Torque stabilized within compare tables and below limits. I’m guessing that the ECU sees one of the limits or there is a single cell or two in the compare tables that aren’t matching close enough and the ETC is commanded to try and meet “bad” data or possibly the ETC itself has a problem when trying to hold position in a very specific, tiny range and it is oscillating. Actual recorded data is the answer source though.

I'll check with our tech and see how I can get that data to you.

I've seen some of your posts in the tuning sections and it sounds like you know quite a bit about how the data is collected and used on these trucks. I'd love for you to look at the data and see what you think. I'll get back to you

I just talked with the tech. The recordings were done with our IDS system and he's not sure if there is an external way of collecting the data. He's going to check it out tomorrow.

 

[FORZDA 1]

I'll check with our tech and see how I can get that data to you.

I've seen some of your posts in the tuning sections and it sounds like you know quite a bit about how the data is collected and used on these trucks. I'd love for you to look at the data and see what you think. I'll get back to you

I just talked with the tech. The recordings were done with our IDS system and he's not sure if there is an external way of collecting the data. He's going to check it out tomorrow.

Ok, I think he can export the data to an external drive (usb stick) as an excel file and then save it. Thanks!!!

 

[03'Darin]

Ok, I think he can export the data to an external drive (usb stick) as an excel file and then save it. Thanks!!!

I asked him about doing it that way but he wasn't sure. That's what he's going to look into

 

[03'Darin]

Ok, I think he can export the data to an external drive (usb stick) as an excel file and then save it. Thanks!!!

Are there specific data logs that you want?

 

[FORZDA 1]

Are there specific data logs that you want?

I'm not sure how the Ford tool breaks down the data, but I would like to see whatever engine data is available. At this point, I'm more focused on the engine performance parameters like pedal position, actual throttle position, Target Load, Actual Load, Throttle Requested Load, Throttle Requested Torque, Torque to Load, Load to Torque, Throttle Inlet Pressure, Throttle Inlet Pressure Target, Throttle Inlet Pressure Max, Manifold Absolute Pressure Actual, MAP Limit Max. etc., etc., etc.... The transmission data may be needed later if nothing unusual shows up in the engine data. I'm expecting to see one or more of the pressure limits, calculated load, or torque limits at or slightly above which is causing the ETC to fluctuate.

 

[VSTOLG4]

Not sure it is even remotely related but starting about 1 week ago I started feeling a stuttering under very light throttle when motor is mostly still cold. Tonight was the first time I noticed the mpg flutter at the same time I can feel the motor stuttering a little. The stutter reminds me of an old 2 stroke dirt bike that would foul a little and then suddenly clean up and pull smooth. When I push the Raptor's gas pedal down a little the mpg gauge is more steady and the motor smooths out. Never noticed this before last week and have had my '18 for about 5 months...with MPT tune. I've cycled a few versions of my tunes this week and the stutter is still there. When the motor warms it goes away. Again, didn't do this until about a week ago. Not saying I have an issue and not saying it is related the OP...just sharing some thoughts. I have MPT tune and SP542 gap @ .025. No codes and Ngauge gauges look clean when stutter happens. Most likely a poor tank of gas or similar but strange nonetheless.