jmiller278

Hello. I have an issue where a low and regular driving, my turbo funtions as expected on my 2013 Eco Boost F150. When at highway speeds of 70+ when I hit a hill, the turbo will seem to stall. Not just 1 or 2 seconds, but almost never kick in.

There is sometimes a noise when I let off the accelerator. Its a whistle, or a chirp. Kind of like a video game noise. A whistle. Not like the whir of the turbos spinning and making the shwooosh noise. This is a short twip right as I let off the accelerator.

Anyway, I took it to the mechanic and they said an O2 sensor was reporting low voltage so they replaced that and tested the system at regular and 'under load' Though I didn't know what under load meant.

I didn't put the 70mph piece together until after they did the work though so I am yet to talk to them again since it is still doing it. They did get a error code, the one I see online about underboost but visual inspection of the turbos looked ok to them.

That's the back story but I wonder if I add some more info if someone has any input.

Many months ago, I got off the highway and as I was pulling in to get fuel at just under 1/4 tank, my engine light came on. I thought oh bummer. I fueled up and when I turned the engine on the light was gone. I still thought there could be an issue so I monitored it for a while but no light returned. Until one day, I went to get fuel @ just under 1/4 tank. The light came on and I noticed the engine kind of wanted to stall, a little rough running.

After getting fuel, the rough ride was gone and after a few miles the light went out.

So I am wondering, and since I am about as much a mechanic as I am an astronaut, I think I have a fuel pump or 2 pumps that may operate at low and high pressure. Is it possible that the high pressure pump is not functioning properly and that is why after running at high speeds I have issues with the turbo.

Since I identified that 1/4 tank gives an error coder, I refuel at just under half a tank so I don't know if it does that anymore or not.

I thought maybe the high pressure tank or inlet may sit differently in the tank and when fuel is low it has issues. But that's my armature analysis.

Any thoughts?

ALso I have 120k miles, I do lots of highway and have a boat that I pull 3 times a year so I'm not very rough on it.

TJPlatinumEB

Lots of questions before anyone can tell you much.

1. How is maintenance on the truck? At 120k miles, how many times have spark plugs and coil boots been changed?

2. When the engine light did or does come on, what was the code?

3. Turbos run off of exhaust gasses and their energy. They can't just turn off or decide to at certain speeds or power levels. What do you mean when you say the turbo never kicks in? Does the truck downshift to speed up? Do the RPM's climb?

4. The whistle you hear when letting off the accelerator is the blow off valve. When you close the throttle, the air that the turbo generated that is not going into the engine has to have somewhere to go. This valve lets it out so no damage is done to the turbos. This is normal.

5. You mention an underboost code. Has this code come back? You can't diagnose it by a visual inspection as you say the shop did. What kind of shop was this? Dealer? Turbo shop of any kind?

6. Usually an underboost code can be fixed by either cleaning the MAF sensor on the intake manifold or replacing it. If it isn't reporting correctly, the computer on the truck can make changes to how it drives that can cause various problems and issues. I've had a number of friends with these trucks and that error code that cleaning and/or replacing that MAF sensor fixes their issues.

jmiller278

Thanks for the reply. Sorry I didn't supply the best info, hopefully this will help.
To answer your questions...
1 - Other than the required oil changes, I think I have had the transmission flushed once. No other engine maintenance that I recall as I had no issues. No plug changes or boots for sure.
2 - I will look up the number code and reply. Its on a sheet they printed out. But it says something to the effect turbocharger under boost. I looked it up online and its a generic error basically stating that the amount of turbo was less than expected for more than like 4 or 5 seconds. Again, perhaps not the best answer, I will return with the actual readout when I relocate my sheet.
3 - Yes, if I want to accelerate or even just maintain speed up a hill, and not even a steep hill the trans. down shifts and the RPMs go about 3k. Normally I would say cruising at 70 is 1.5k and in the past it would maybe get up to 2 or close to it with the turbos helping. Now going up a hill with the cruise on will eventually slow down to where the engine has to take over, downshift and rev up to get the power needed to maintain speed.
4 - Thanks for the explanation. I've heard that sound on videos of souped up cars and while theirs is longer an louder, this does sound similar.
5 - the code was cleared by the repair shop and it did come back. I didn't drive on the highway for like 4 days and it went out. Then once I went back on the highway it came on again. I was driving on the hwy 2 days ago and it came on again. I suspect it will go out tomorrow perhaps. I have some driving non highway this week and I guess if I put enough cycles in without underboost, it will go off. Its not a turbo shop at all, just a place I trust to perform my oil changes, tires, etc. so I think this is likely over their wheelhouse. As for the visual inspection, I think they were looking at hoses or checking if things spin correctly. At least that's what I take that to mean from the youtube videos Ive watched.
6 - Thanks for the suggestion. I will consider this for sure.

I just am looking for info to help with the diagnosis. I don't want to keep taking it in at HOWEVER many dollars a pop to have someone say... well, its not doing it now and we've cleared the error so...

But I will research the MAF sensor to see if that's something I can do or someone with more skill than me.

TJPlatinumEB

Based on what you are saying and with the mileage your truck has, DEFINITELY change plugs and boots and clean that sensor. At the very least it will improve the driveability of the truck. Plugs should be done roughly every 30k miles, so you really need to do those.

If you go to an auto parts store and tell them you need MAF cleaner, they will sell you a product that is safe to use on that sensor. Remove it, clean it, and put it back in. That along with the plugs and boots will probably make a huge difference.

jmiller278

Great suggestions. I watched a video on the MAF cleaner and that seems easy enough. The plugs... eh, well that's probably something better left to my trusty repair man. But I will certainly get that done. Even if that's not the culprit, it sounds like it could be a net positive for my ride. Thanks again!

jdunk54nl

I agree the plugs need to be changed too.

However, have you tried doing a KAM (Keep alive memory) reset? This resets all of the learned adaptations (settings) on the truck.

Easy to do. While the truck is cold, unhook negative side of battery, take a jumper wire and connect the positive side cable to the negative side cable making sure the negative side is covered up so it can't touch anything.

Leave it like that for 10 minutes. Then start the truck and let it just idle to operating temperatures or about 20 minutes.

This should definitely be done after any sensor cleaning, air filter change/cleaning, and plug/boot changes. It allows the truck to re-learn all of the fuel trims and air trims as well as transmission habits.

jmiller278

However, have you tried doing a KAM (Keep alive memory) reset? This resets all of the learned adaptations (settings) on the truck.

I did do that actually. Not exactly how you mentioned. My note I found was to turn the lights on and disconnect the terminals. Let it sit for 30 min and then reconnect. Then, turn the key but not to start, just accessories. Then press the gas slow to the floor then release quick and turn off. Repeat 4 more times.

So that's what I did. My clock and stuff reset so I assumed it cleared the memory but the engine light did not reset after that. I was too lazy to try once again.

jschmidt

Bad plugs would throw a code too. But you should change them just do you can change them when you need to. Get a cheap code reader from Amazon to help you diagnose this problem. A lot of your symptom list sounds like it could just be normal. You really need to read the code and google it.

j20brett

Underboost can be a torn diaphragm in the blow off valve also. Its a $20 part.

kruman

Where can I find just the diaphragm and not the whole assembly. Do you have a part number ? Thanks