Ford Says no PCM Problem
09-27-2014, 09:25 AM
#21
My truck is stock no mods V8, 6 speed, and 3.31 axle
To further explain my issue this is a more precise breakdown of one of my videos.
Be aware there is a lag in the rpm/mph readings due to the gauges being analog. This lag is present while increasing or decreasing (rpm/mph) – they will not track precisely during these short time intervals.
Video is 20.27 sec
Starts as stated before in my OP; I am not touching the gas pedal during any of the following sequence.
At ~ 18-19 mph- 3rd gear ~950 rpm idling along - SLIGHT downhill grade
Pressing the brake to slow down – (NOT STOPPING) takes about 10 sec (It's at about 9 sec that I let off the brake)
At 10.03 seconds it is in 3rd gear, slowed to ~600 rpm, at ~2.5-3 mph
At 10.08 it shifts to 1st,
************************************************** ****************
It immediately begins to rev up and increase in mph and continues for 3.75 sec
At 13.83 seconds it is STILL in 1st ~2050 rpm and 14 mph
Then RPMs begin to back off
At 15.17 it is STILL in 1st, 1250 rpm and 17mph (a drop of 800 rpm)
************************************************** ****************
In the above sequence PLEASE do not focus on mph - the vehicle is on a slight hill
Focus on the fact that rpms start increasing and continue to increase for 3.75 sec until
the tach shows 2050, then back off by 800 all by itself
It backs off for 1.37 sec, (13.83 to 15.20 – see below at the shift point)
At 15.20 seconds it shifts to 2nd, rpm drops to 1050 at 17 mph
At 16.47 it is STILL in 2nd, 1100 rpm at 20 mph
At 16.60 seconds it shifts to 3rd, rpm drops below 1000
I am well aware of the diff of (~2050 rpm and 14 mph) and (1250 rpm and 17mph) while in 1st gear.
The rpm increased by 1450 (650 to 2050), over a period of 3.75 sec.
The rpm drops off by 800 over a period of 1.37 sec. b4 it shifts to 2nd
This is 5.12 seconds that it is in 1st while it revs up then settles down and finally shifts up to 2nd.
This is all while no input from the accelerator.
I’m well aware of the physics of momentum-force, feedback via wheel rotation, transmission speed and engine speed. I haven’t calculated the change in the elevation of the hill where the video was taken. The distance in the above scenario is about 100-150ft at most – this is not an elevation drop of 100-150ft. An increase in rpm shifting from 3rd to first is normal – but I feel this amount is not.
I’m trying to understand why the PCM is doing this. I will do a couple of more videos today and post my findings. Thanks for all constructive feedback.
To further explain my issue this is a more precise breakdown of one of my videos.
Be aware there is a lag in the rpm/mph readings due to the gauges being analog. This lag is present while increasing or decreasing (rpm/mph) – they will not track precisely during these short time intervals.
Video is 20.27 sec
Starts as stated before in my OP; I am not touching the gas pedal during any of the following sequence.
At ~ 18-19 mph- 3rd gear ~950 rpm idling along - SLIGHT downhill grade
Pressing the brake to slow down – (NOT STOPPING) takes about 10 sec (It's at about 9 sec that I let off the brake)
At 10.03 seconds it is in 3rd gear, slowed to ~600 rpm, at ~2.5-3 mph
At 10.08 it shifts to 1st,
************************************************** ****************
It immediately begins to rev up and increase in mph and continues for 3.75 sec
At 13.83 seconds it is STILL in 1st ~2050 rpm and 14 mph
Then RPMs begin to back off
At 15.17 it is STILL in 1st, 1250 rpm and 17mph (a drop of 800 rpm)
************************************************** ****************
In the above sequence PLEASE do not focus on mph - the vehicle is on a slight hill
Focus on the fact that rpms start increasing and continue to increase for 3.75 sec until
the tach shows 2050, then back off by 800 all by itself
It backs off for 1.37 sec, (13.83 to 15.20 – see below at the shift point)
At 15.20 seconds it shifts to 2nd, rpm drops to 1050 at 17 mph
At 16.47 it is STILL in 2nd, 1100 rpm at 20 mph
At 16.60 seconds it shifts to 3rd, rpm drops below 1000
I am well aware of the diff of (~2050 rpm and 14 mph) and (1250 rpm and 17mph) while in 1st gear.
The rpm increased by 1450 (650 to 2050), over a period of 3.75 sec.
The rpm drops off by 800 over a period of 1.37 sec. b4 it shifts to 2nd
This is 5.12 seconds that it is in 1st while it revs up then settles down and finally shifts up to 2nd.
This is all while no input from the accelerator.
I’m well aware of the physics of momentum-force, feedback via wheel rotation, transmission speed and engine speed. I haven’t calculated the change in the elevation of the hill where the video was taken. The distance in the above scenario is about 100-150ft at most – this is not an elevation drop of 100-150ft. An increase in rpm shifting from 3rd to first is normal – but I feel this amount is not.
I’m trying to understand why the PCM is doing this. I will do a couple of more videos today and post my findings. Thanks for all constructive feedback.
Last edited by Lee 2012 F150 XLT; 09-28-2014 at 10:58 PM. Reason: Showing where I let off the brake
09-27-2014, 10:43 AM
#22
have you done the battery discconnect, that will set transmission back to factory default shifts. your truck has an adaptive learning tranny. look at a You Tube video how to correctly drain off the voltage. sounds like the way my wifes Flex acts when i use the hill assist, stays in lower gears and rpms rev up. i do the battery disconnect to my wifes car every 6 months or so and shifts great. seems the way she drives it shifts lazy is the only way to describe it. our 6 speeds are geared really low in first gear, that an drive by wire the trann ymaybe getting confused. while you got battery down, clean the posts and put some no ox on the posts.
white08gt, I see you live in Collierville, my in-laws live in Cordova. They found my truck at Landers last Aug. I will attempt your advice sometime next week after I read up on it and get a little more feedback.
09-27-2014, 11:17 AM
#23
Senior Member
People have already told you why, its to slow the truck down
You dont think tractor trailers use their brakes going downhill do you,?
When you drove stick when you slowed down did you just pop it into neutral and ride the brakes?
These trucks are 6000lbs+ and use a modern high pressure auto that uses its gears to assist in holding a steady speed not an old slushbox you need to ride the brakes going downhill or else you just keep gaining speed.
Another reason is to have the truck so when you slow down its in the proper range to accelerate with minimal throttle imput. What works better speeding up in a lower gear with 20% of the throttle body open or in a higher gear with 50%-70% of the throttle body open?
You dont think tractor trailers use their brakes going downhill do you,?
When you drove stick when you slowed down did you just pop it into neutral and ride the brakes?
These trucks are 6000lbs+ and use a modern high pressure auto that uses its gears to assist in holding a steady speed not an old slushbox you need to ride the brakes going downhill or else you just keep gaining speed.
Another reason is to have the truck so when you slow down its in the proper range to accelerate with minimal throttle imput. What works better speeding up in a lower gear with 20% of the throttle body open or in a higher gear with 50%-70% of the throttle body open?
09-27-2014, 01:50 PM
#24
People have already told you why, its to slow the truck down
You dont think tractor trailers use their brakes going downhill do you,?
When you drove stick when you slowed down did you just pop it into neutral and ride the brakes?
These trucks are 6000lbs+ and use a modern high pressure auto that uses its gears to assist in holding a steady speed not an old slushbox you need to ride the brakes going downhill or else you just keep gaining speed.
Another reason is to have the truck so when you slow down its in the proper range to accelerate with minimal throttle imput. What works better speeding up in a lower gear with 20% of the throttle body open or in a higher gear with 50%-70% of the throttle body open?
You dont think tractor trailers use their brakes going downhill do you,?
When you drove stick when you slowed down did you just pop it into neutral and ride the brakes?
These trucks are 6000lbs+ and use a modern high pressure auto that uses its gears to assist in holding a steady speed not an old slushbox you need to ride the brakes going downhill or else you just keep gaining speed.
Another reason is to have the truck so when you slow down its in the proper range to accelerate with minimal throttle imput. What works better speeding up in a lower gear with 20% of the throttle body open or in a higher gear with 50%-70% of the throttle body open?
t.mackenzie
Are you sure that you read my posts correctly? The truck has already slowed down to ~2.5-3mph. It’s an automatic, how else do you slow/stop an automatic on a slight downhill grade? In my 40 plus years of driving I have experience with both manual and automatic trucks/cars. I learned how to drive using a manual in the mountains where I grew up. I currently own a RX7-5 speed manual (27yrs), a VW Jetta 5 speed manual (14yrs). I am very familiar with using a manual tranny – down shifting to reduce speed b4 coming to a complete stop. If you have time, please re-read my OP, then re-read my post #21. As I stated very plainly the speed is reduced to ~2.5-3mph at the downshift point from 3rd to 1stb4 the PCM/CPU revs the rpm back up to ~2050 - why does it think the rpm should be 2050 in 1st at ~2.5-3mph. I am slowing it down with the brake which is what most people do when driving an automatic. If I engage the accelerator while the PCM/CPU is causing the rpm to increase it will often go above 3000 rpm before shifting.
"What works better speeding up in a lower gear with 20% of the throttle body open or in a higher gear with 50%-70% of the throttle body open?"
This question doesn’t make sense relative my issue.
It accelerates fine in all conditions.
09-27-2014, 02:11 PM
#25
Senior Member
Try this: Use the button on the shift lever to keep the truck in first. Accelerate to 2.5mph and hold it steady. Read the RPM. Accelerate to 3mph and hold it steady. Read the RPM. Report back to us. First is a very low gear (4.17:1) I'd suspect that the PCM is programmed to 'blip the throttle for the 3-1 downshift to make it smoother just like we used to 'double-clutch' a manual.
OK after re-reading post #16 I think I understand you said that after the truck slows to 3mph or so and has shifted into 1st, it accelerates to 15-17mph in first with your foot on the brake? Is that right?
OK after re-reading post #16 I think I understand you said that after the truck slows to 3mph or so and has shifted into 1st, it accelerates to 15-17mph in first with your foot on the brake? Is that right?
09-27-2014, 02:13 PM
#26
sounds to me like you wont find the answer here. you need someone to properly assess the issue in person. it also seems like you dont want to actually hear another answer other than the PCM is wrong, you have established this mindset already, imposible to change. sort of like my grandfather who thinks his truck accelerates better from a stop with overdrive off, even though overdrive is only locking out the last gear. doest matter he wont hear any different.
My advice try another dealer, or try changing driveing style to see if it helps. try the battery trick.
My advice try another dealer, or try changing driveing style to see if it helps. try the battery trick.
09-27-2014, 03:43 PM
#27
Try this: Use the button on the shift lever to keep the truck in first. Accelerate to 2.5mph and hold it steady. Read the RPM. Accelerate to 3mph and hold it steady. Read the RPM. Report back to us. First is a very low gear (4.17:1) I'd suspect that the PCM is programmed to 'blip the throttle for the 3-1 downshift to make it smoother just like we used to 'double-clutch' a manual.
OK after re-reading post #16 I think I understand you said that after the truck slows to 3mph or so and has shifted into 1st, it accelerates to 15-17mph in first with your foot on the brake? Is that right?
OK after re-reading post #16 I think I understand you said that after the truck slows to 3mph or so and has shifted into 1st, it accelerates to 15-17mph in first with your foot on the brake? Is that right?
Feathermerchant, this is exactly the type of feedback I’m looking for. I have looked at the specs for my vehicle, here they are – I will just show the gears I’m dealing with.
1st4.17:1
2nd2.34:1
3rd1.52:1
Standard final drive2.17:1
Axle ratio3.31
Does anyone know where I can find the formula to calculate speed based upon engine rpm? I have seen formulas but they don’t include both Standard final drive and Axle ratio. May just be a mistake on my part of understanding the terminology. I will have to also include the diameter/circumference of the tires – depending on the formula. I will check for more formulas.
Your suggestion - Try this: Use the button on the shift lever to keep the truck in first. Accelerate to 2.5mph and hold it steady. Read the RPM. Accelerate to 3mph and hold it steady. Read the RPM.
I don’t think this is doable. I can use the button to hold it in first, but I’m on a slight downhill grade, my gauges are analog, and I’m trying to give my best estimation as to the actual speed/rpm looking at a video frame by frame. (difference between 2.5 & 3 is really not discernible)
I let off the brake at ~ 2.-3mph, about 9 secs into the video and leave it off.
See my post #21 for a better breakdown of events.
Thanks
Last edited by Lee 2012 F150 XLT; 09-28-2014 at 11:18 PM.
09-27-2014, 04:24 PM
#28
Based on my own experience and reading about others on this and other forums , these trucks are weird and strange compared to all other vehicles on the planet. It either drives you mad or does not bother you at all .
The following 2 users liked this post by 77_Jimmy:
Lee 2012 F150 XLT (09-27-2014),
Wanted33 (09-29-2014)
09-27-2014, 04:44 PM
#29
sounds to me like you wont find the answer here. you need someone to properly assess the issue in person. it also seems like you dont want to actually hear another answer other than the PCM is wrong, you have established this mindset already, imposible to change. sort of like my grandfather who thinks his truck accelerates better from a stop with overdrive off, even though overdrive is only locking out the last gear. doest matter he wont hear any different.
My advice try another dealer, or try changing driveing style to see if it helps. try the battery trick.
My advice try another dealer, or try changing driveing style to see if it helps. try the battery trick.
I apologize if I seem a little hard-headed. I’m more than willing to hear another answer other than the PCM, please look at my post #21 – it better describes the issue showing speeds, rpms, shift points and time. Again, I apologize if I seem hard-headed, it’s just that based upon some of the feedback I’m getting it doesn’t appear that I have clearly explained the issue or it is not understood. I spent 20 minutes telling my neighbor, he still didn’t get it until I took him for a test drive – then he had that a-ha moment.
The first time I took it to the dealer, they hooked a laptop to the OBD connector and recorded everything that was happening. They clearly saw the run-away rpm issue I'm trying to describe. I don’t know why they didn’t see recorded data that was similar to this issue as I have described in post #21. In fact he should have seen when I applied the brake, when I let off the brake, the mph, rpm, shift points and duration of the rpm increase, etc.
I have an appointment with another dealer Monday; unfortunately after talking with the mechanic/technician on Friday he said he has never heard about this issue, I will gladly demo it for them.
This morning while doing a couple of test runs I met another neighbor who has the 3rd 2013 F150, he said his does the same thing as mine at the stop sign when he does a rolling-stop, not a complete stop. He has a 3-4 yr old Cadillac – it doesn’t do it.
My Odyssey doesn’t do it, I know the Caddy and Odyssey have different trannys – designed for completely different conditions – I’m just trying to better understand the 6 speed truck tranny and PCM.
Hopefully someone can point one me to a consumer software package, I’ll use one of my laptops and try to diagnose a little. If not maybe point me toward a “Tuner” that has experience with this vehicle.
I’m here to find answers and better understand my truck – I like it – I just want to like it more.
09-27-2014, 04:54 PM
#30
I was told by an old man when I was a young child that “If you beat a dead horse long enough, it will sooner or later get up and run.” The old man seemed pretty honest to me. So this issue is my dead horse. J