2017 ecoboost 2.7 performance issue when towing

351 Views 13 Replies 6 Participants Last post by RitzMontana, 9 d ago

RitzMontana

Discussion Starter · 11 d ago

Hi all – sorry for the long post but I’m trying to lay out my total, year-long experience on this issue. I have yet to see any forum discussion on this specific topic (but I'm new here!).

I have a perplexing issue with towing performance with my 2017 F150 2.7 Ecoboost, which I bought last summer and now has 31k miles. I’ve been to two dealers to try to diagnose this potential issue, but with no resolve. The truck runs great without towing, even on full boost, using 87 octane gas (probably why the dealer couldn’t find anything wrong), and the 2.7 Ecoboost has plenty of power for my towing needs – but only if using 91 gas as I describe below.

I live and typically travel at high (5000+ ft) elevation and after buying the truck it took me a while to learn about what gas to use when towing. When I connect my 3000 lb trailer and use 87 gas, it runs really poorly – loud exhaust, rough and weak. Tail pipe is sooty, and spark plugs get completely black indicating a very rich AF mixture (that happens even when using 91 gas). It’s my understanding that turbos will run rich under high boost to prevent excessive combustion temps, but in this case it seems to be overdoing it. No blackening of the plugs occurs when not towing. I changed plugs and filters and cleaned the MAP sensors, but with no improvement. I eventually found that running 91 octane gas exclusively definitely helps it run smoother but with the side effect of the throttle response getting sluggish: I really need to press hard on the peddle to get it to shift down. Maybe because the ECU loves to keep the engine at lower RPM when running premium, but power and pep seems to be lacking and when cruising at 1600 RPM it still seems to run a bit rough.

Interestingly, yesterday I dropped off the trailer at the storage yard a few miles away, driving with the trailer plug disconnected (on a rural road with no traffic) and it ran perfect on 87 gas (after my first fill-up with regular gas after my recent 2000 mile desert SW trip where I ran 91) with very good pep – just like it should run. Maybe the ECU got trained from the 91 gas to run differently, but this is probably temporarily. Importantly, I question why in my case it stinks to use 87 gas and it takes 91 gas to get the engine to run decently, when many say 87 should work fine.

Does anyone have any experience about this issue and how to resolve it? Is there a test (using Forscan) that will detect a fault in the system? Will an engine tuner to modify timing help? Or is it just a matter of accepting the fact that 91 gas is necessary for towing and sub-par performance can be expected? Thanks!

Kerry
Bozeman, MT

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FanaticalKilla

· #2 · 11 d ago

I would start right off the bat with a KAM reset. Pull the negative battery cable over night. After you reconnect. Do a throttle relearn. When you changed spark plugs did you do coil boots as well?

Could pull charge air piping and check for condensation in the intercooler. Sounds like the truck is on the verge of a underboost code.

Forscan is a great idea. So much data to be had! You also will be able to see soft codes before they become permanent. Also you’ll be able to monitor other sensors.

There are a couple tuners that are open to reviewing data logs and helping you understand data. Only issue is you’ll probably need an SCT device or a HPT device.

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mass-hole

· #3 · 11 d ago

I would scan for codes with forscan.

I would also check your Octane Adjust ratio and fuel trims when running on 87 gas. And when you are towing. You can use the Forscan mobile app for all of this.

87 should run fine, I towed with it in my 2014 for a few years before the prices here in Utah got within 20 cents and started running 91 100% of the time. 91 is prefered when towing for sure.

I almost wonder if you are have a leaky blow off valve or boost leak or something. Its common for the BOV diaphragm to tear. Thats why when the truck is not towing it runs ok, but when you start towing it runs more boost pressure and the problem presents itself.

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RitzMontana

Discussion Starter · #4 · 10 d ago

Good suggestions. I have a Forscan adapter on order and will start with that. I also have a local SCT custom tuner that I can meet.

Regarding the first comment - no, I didn't replace coil boots as the truck had pretty low miles (about 25,000). I have pulled the battery cable off before, but only for a short time. I'll do it overnight.

Another piece of evidence that I didn't mention: the engine exhaust is particularly loud when starting up cold. Then after 20 seconds or so something switches and most of the sound goes away. But there have been times when the engine sounds like a diesel truck when cold and this takes a while to quiet down. Sort of embarrassing at campgrounds! I need to get down under the truck with a listening tube to see where the noise is coming from. Sounds like something is cracked, which closes up at it warms up. I can also pull the BOV, but will I be able see if the diaphragm is torn by taking it apart?

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2016XLT4x4

· #5 · 10 d ago

Use "Tow/haul" mode and lock out your overdrives when towing. Running a higher octane when towing is also suggested in the owner's manual.

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butthead

· #6 · 10 d ago

Just because you can, not everything in the "can do" is a good practice. Octane is one area I do not skimp on with a small turbocharged engine, too much to go wrong. Anothe personal thought is the habbit of lugging the engine. Operating at 1500 RPM and relying on boost to maintain or increase speed. Again hard on small turbo engines. You truck is equipped with transmission gear lock outs, easy to use. Lock out the upper gears to keep the engine RPM in a better power range, on my 20-17 2.7 that is 2000 RPM or higher if haling a load.
Definatly look for maintanence problem and part failure but a lot of problems can be addressed in the manner of useage. KM

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RitzMontana

Discussion Starter · #7 · 10 d ago

Yes, keeping it out of O/D to avoid lugging is necessary but somewhat a nuisance, having to set it up every time you shift into gear.

I just got Forscan running using a OBD2 USB adapter and am starting to learn it. Running diagnostics didn't find anything, but I really don't know what to look for. I'll look for a primer in the forum. As recommended above by mass-hole, I checked the "learned relative octane adjustment", which is -3.96%. (-0.0396?). And boost (TCBP) is like 32 psi at full throttle, dropping to 12.4 at idle. I feel real stupid right now

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Gord0

· #8 · 10 d ago

Is that -.0396 on 87 octane? 91-93 octane should get you to around -.99 which is as good as you can get.
Looks like you might not be reading the right pid for boost.

As others have said, KAM reset along with throttle relearn is a good place to start. Motorcraft plugs of the correct heat range and gapped to .028-.030"? Any modifications done to the truck? New air cleaner?

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butthead

· #9 · 10 d ago

"Yes, keeping it out of O/D to avoid lugging is necessary but somewhat a nuisance, having to set it up every time you shift into gear."

Not sure how you approach this but on my 2017 it is simply a +- rocker on the shift column. On console option this switch is on the side of the shifter. Literally just push a button. KM

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mass-hole

· #10 · 10 d ago

Gord0 said:
Is that -.0396 on 87 octane? 91-93 octane should get you to around -.99 which is as good as you can get.
Looks like you might not be reading the right pid for boost.

As others have said, KAM reset along with throttle relearn is a good place to start. Motorcraft plugs of the correct heat range and gapped to .028-.030"? Any modifications done to the truck? New air cleaner?

I believe OAR is flipped on forscan. +100% is good. At least on my 2014. Mine always runs at +100 when HPTuners reports -1.

So he is actually running a little on a bad side of zero. Which i think is normal for 87, my dads stock expedition was just positive of zero when I looked.

His boost PID is probably the TIP sensor and is reporting in absolute pressure. thats why its reading 12.4 at idle, which is probably his ambient pressure at 5000'

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RitzMontana

Discussion Starter · #11 · 10 d ago

Gord0 said:
Is that -.0396 on 87 octane? 91-93 octane should get you to around -.99 which is as good as you can get.
Looks like you might not be reading the right pid for boost.

As others have said, KAM reset along with throttle relearn is a good place to start. Motorcraft plugs of the correct heat range and gapped to .028-.030"? Any modifications done to the truck? New air cleaner?

No mods on truck New OEM Motorcraft plugs and air filter around 6000 miles ago. A boost of 32 psi minus 12.4 (atmospheric pressure at 5000 ft) equates to a boost of 19.6 psi. That seems very high. I'll check again today.

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FanaticalKilla

· #12 · 10 d ago

mass-hole said:
I believe OAR is flipped on forscan. +100% is good. At least on my 2014. Mine always runs at +100 when HPTuners reports -1.

So he is actually running a little on a bad side of zero. Which i think is normal for 87, my dads stock expedition was just positive of zero when I looked.

His boost PID is probably the TIP sensor and is reporting in absolute pressure. thats why its reading 12.4 at idle, which is probably his ambient pressure at 5000'

My OAR in my 2017 with Forscan is negative good, positive bad.

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Gord0

· #13 · 10 d ago

mass-hole said:
I believe OAR is flipped on forscan. +100% is good. At least on my 2014. Mine always runs at +100 when HPTuners reports -1.

So he is actually running a little on a bad side of zero. Which i think is normal for 87, my dads stock expedition was just positive of zero when I looked.

His boost PID is probably the TIP sensor and is reporting in absolute pressure. thats why its reading 12.4 at idle, which is probably his ambient pressure at 5000'

I figured he was pretty close to normal for the oar with 87.

I thought the same for the psi reading, but shouldn't be also be pulling vacuum at idol?

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RitzMontana

Discussion Starter · #14 · 9 d ago

Thanks so much for providing very useful input! Now that I understand OAR, time to move on to my original issue relating to the engine running rich (mainly pulling my trailer). I took a joyride with my camper trailer and tablet, taking screen shots of certain Forscan parameters. Four cases are shown below: with and without the trailer modules active, and low-load and high load (i.e., boosted). The engine seemed to run strong and smooth in all cases. Max boost seems around 15 psi (relative), and when I disconnected the recirc pipe from the BOV it burps at the right time (rapid release of throttle). Granted, this isn't a rigorous test, but should be informative.

Observations:
1. Long term fuel trim seems rich (positive trim ranging between 2% and 8%), averaging about 5%. One cell that has a negative trim (-3%), but I don't know what that means. I don't know how many miles the LTFT averages over, and could be biased by trailer towing a while back (maybe 100 miles).
2. Short term fuel trim: With trailer control disconnected, it is close to zero whether boosted or not. But with trailer control connected the STFT goes to -4 to -5.5 under boost (-2 to -3 when not boosted). Why would the trailer control be causing it to lean out ?

I read that a code won't be triggered until the fuel trim exceeds +/- 15%.

If there is a better test procedure to follow, please recommend!

Boosted, Trailer Control Connected:

Boosted, Trailer Control Disconntected:

Light Load (no boost), Trailer Control Connected:

Light Load (no boost), Trailer Control Disconnected

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