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Turbo Lag and Causes

6K views 21 replies 12 participants last post by  Engineer 
#1 ·
My 2017 Ford Fusion Sport was purchased in February of 2018. It has 12,000 miles. We love the car and the way it performs. But recently it feels like something is pulling it back. It doesn't feel as smooth or as powerful. What would cause this to happen. Our diving is mostly city driving --- not a lot of highway driving. It's extremely disappointing to not have the full power feeling. Is it tubo lag, or a sensor that has failed? please help thanks
 
#2 ·
Hi @vbcello hopefully you'll get some good answers on what might be happening there. Probably the best way to get the data would be to data log and make some pulls (acceleration under controlled conditions while logging the data). Alternatively, you could scan for codes and see what comes back.

As far as turbo lag, I think that's unlikely to be the cause. These cars don't get much turbo lag. Despite how popular it is to talk about, these cars don't see much turbo lag because we use twin turbos and they're both on the smaller side, meaning they spool up really quickly. So there's not likely to be much lag there.

One thing I've noticed on these cars is that how they respond depends, to some degree, on how they're driven. If my wife drives my FFS, I notice it becomes considerably more tame after that until I reset my PCM. I imagine it would eventually re-learn just based on my driving, if I waited long enough, but I just don't have the patience because it's so much less responsive after she's driven it. So I just reset it and then it's fine.

What octane are you running? Do you have a performance tune? Higher octane gas increases power and responsiveness, even stock, but especially of course if you have a tune.
 
#3 ·
Thanks so much for responding! I do use the highest octane gas. Can you please explain what PCM is and how to re-set it? When you say "have a tune" are you talking about a conventional tune-up. The car only has 12,000 miles. If a "tune-up," what would accomplished by it?
 
#4 ·
Hi @vbcello ! The PCM is the "Platform Control Module". It's the computer that manages your engine, transmission, Intelligent All-Wheel Drive system, and so on. Basically anything related to the drivetrain/powertrain components is managed by the PCM.

There are a few ways to reset it, but what I personally typically do is just reset it with my tuner because I own a tuner that I can plug in and use to do that (among other things).

Have you checked the air filter? A dirty air filter is a fairly simple thing to fix, but it's a common cause of power loss on pretty much any fuel-powered car. I would definitely check (or just replace) the air filter.

The air filter and a simple code check would be a good idea. You could probably even get these done at a lot of auto parts stores for free (other than the cost of the filter) depending on where you go.

I would suggest buying a tuner, but you probably don't want to do that yet because it will affect your warranty. Since you're still under warranty, that's probably not what you want quite yet. But if you eventually do decide to get a tuner, you can significantly increase the power/performance/responsiveness of these cars.

Another thing: Are you driving in Normal or Sport mode? Sport mode should make the car more responsive and lively.
 
#7 ·
Hi, thanks for your response. Another thought I have is that the sluggish power feeling, and seemingly not opening up full-throttle could possibly be a transmission issue. Maybe the transmission is not switching to the highest gear. We had a 30-mile trip yesterday with speeds from 45 to 75 and at all speeds the engine felt like it was being held-back. I plan to take it to the dealer soon. What diagnostics should I request, i.e. - full engine diagnostics? Are there diagnostics I should ask them to run on the Transmission? Thanks
 
#5 ·
Hey, @vbcello;
Good luck with finding the issue. My only thing I can add, is that here in Louisiana after hurricane Ida, I experienced the same thing. I'm under the impression that my local fuel stop put some type of less-than-premium gas in the premium dispenser during the fuel scarcity issues we experienced. The problem went away about 10 minutes after a fill up with good, premium fuel.

The good news is that if the fuel isn't actually premium, the car's computer can handle it and prevent damage to the engine by pulling timing, which is likely contributing to the reduced power feel you're experiencing. Mine felt almost exactly as you've described... just one day got in the car and it had way less power and "get-up" than it typically does. Nothing obviously wrong with it, no lights on the dash, no big changes in my driving behavior, just simply reduced power. I was planning on having it checked out when I put fresh gas in it, and about 10 minutes after the fill up, the car suddenly came to life, leading me to believe it was an issue with the quality of the fuel.

I'd only become worried if this keeps happening after you've run most of this tank out, filled with a quality premium gas, and then if the car continues the laggy-ness, you'll know it isn't the fuel.

These cars are designed to reduce power on poor quality fuels, so this could absolutely be what you're experiencing.

Best of luck, and hope you get many more miles of enjoyment out of the Fusion.

Best,
Dustin
 
#6 ·
Turbo lag refers to the time it takes for the turbos to spool up after you hit the gas. This was an issue in the 90s and early 2000s when cars had large single turbos - you'd floor it and nothing would happen for a second or two until the turbocharger spun up enough to create additional pressure. On our cars this isn't an issue, since, as @Engineer mentioned above, we have two small turbos - they're very quick to spool up so there's essentially no lag.

A "tune" is an aftermarket modification that reprograms the car for increased performance. It certainly doesn't sound like you have one.

A "tune-up" is basic maintenance so certainly not a bad idea. Changing the air filter was a good suggestion, as it sounds like the car is running fine but not breathing well. Using quality premium gas is another good suggestion - I would highly recommend sticking with Top Tier stations, such as Shell and Exxon/Mobil. Look around the engine bay for rodent nests or leaves too.
 
#9 ·
Hi vbcello. In addition to the good information and help you have already received above: Your Fusion Sport is still within the 5 year/60,000 mile Powertrain Warranty. Perhaps make a service appointment to have your vehicle checked for any underlying issues, while still within the Powertr5ain Warranty.

I would also recommend: It can be hard for a Tech to determine and find an issue on their own, just by being told some variation of "My car seems to have something holding it back or turbo lag".
Therefore, when you bring your vehicle in, ask the Service Writer to send a Tech for a ride with you (or go themselves), so you can demonstrate exactly what the issue is. Then you can drive your Fusion exactly in a way that will cause your concern to occur. Then get them to clearly state that yes, they feel it too.

In this way, you can hopefully avoid the dreaded "Could not duplicate the customers concern" non-diagnosis.

I do understand that service appointments can be a pain, but it is usually the best way to address an issue.

Let us know how you make out and good luck.
 
#10 ·
Vbcello, driving myself in LA I got some time the same feeling that you, the car becoming less responsive.
I found 2 work-around:
1) Placing the car in Sport mode and revving up a bit the engine.
2) Resetting the gas pedal.
For that you need to place the car on but without starting the engine.
Push slowly the gas pedal to the floor stop and then release the gas pedal as fast as possible.
Shutdown the car and that is it, the gas pedal is reset.

Remember that during winter time the gasoline is different and the cars are less powerful (at least mine and my wife's).
 
#18 ·
Remember that during winter time the gasoline is different and the cars are less powerful (at least mine and my wife's).
Some other ideas:
The brakes are dragging or emergency brake not fully disengaged​
The membrane in the OEM blow off valve is damaged​
Air leak (air box not fully sealed, loose vacuum hose, loose clamps in intake tract)​
Long term fuel trim needs to be reset​
Clogged catalytic converter or exhaust​
You would think some of that stuff should throw codes at least.
 
#11 · (Edited)
Not sure where you live, but this time of year is usually a huge power increase, even stock, due to much denser air.
If you feel it is less powerful now than it was in the summer (unless you live in say southern Cal, where temps barely change or something),
then you really have an issue.

Remember that during winter time the gasoline is different and the cars are less powerful (at least mine and my wife's).
Typically untrue. Air density is almost always higher in the winter, which means more air in the engine (and potentially more power).
Winter gas, may have more ethanol, which reduces gas mileage, but computer compensates making A/F ratios the same as summer.

If anything, the reduced heat in engine (and heat soak of IC), the miniscule increase in average octane from extra ethanol, and the increased air density,
means power almost always goes up. Some years I even remove 93 tune in the dead of winter, as power really spikes in winter and I just don't need that
extra power in the snow.
 
#12 ·
From my experience on a feeling of under performance I found:
1. Use sport a bit more. The car has an algorithm that adjusts the throttle response and power delivery to the driving style being applied as indicated by a couple of replies above. Basically if you are driving economically the car will change the way it responds. Using sport mode changes gears at higher revs and alters the algorithm. Not an instances change, will take a few trips with a bit more aggressive throttle input. This issue is the most common to me. After a week or so of peak hour traffic, the car response is more subdued and changing lanes and overtaking takes a bit more time (well it feels like it anyway).
2. Gas quality. Car was sluggish, running a bit rough and with terrible fuel economy, I changed gas stations and providers (Esso to Shell in this instance). After 2 or 3 fill ups there was a noticeable difference. I am positive the octane level from this specific station was lower than it should have been and contaminated.
3. The power is sensitive to temperature. Make sure you radiators are clear of leaves, particularly the bottom intercooler for the turbos. These don't need to be covered much before the engine starts derating.
4. Check the air intake filter. Easier still is get the service guy to change. It quick and cheap. The paper filters can get blocked easy in dusty environments. If the engine can't breathe it can't make power.

Side notes. I'm assuming you are maintaining the vehicle correctly, changing fluids regularly. As mentioned turbo lag is the delay of the turbos kicking in, you still get full power with turbo lag. There could feasibly be a transmission issue however I think you would feel this more with harsh gear changes. Real issues typically result in alarms and the car going into limp mode, not derating power. Lastly fresh oil is your friend.

Its difficult to quantify power loss and even trickier to diagnose, however the suggestion of taking a mechanic on a drive and demonstrating what you mean may help the mechanic look for the usual suspects, but I would try the above items I mentioned as these may get suggested first off by the mechanic. Having answered to these when you go in will hopefully mean he starts looking at things you can't.

Good luck. Hope all the advice helps. Glad you've been enjoying the car. Welcome to the forum.
 
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#13 ·
Hello @vbcello. All the folks above have offered great advice. I would like to add my 2 cents. Based on the info you provided in your initial post, you stated you have a 2017 Model that you have had since 2018 and only have 12,000 miles on it. That is 5 years (car was probably built in 2016) with an average of 2400 miles a year. I would bet that your car still has the original battery and may have only had 1 or 2 oil changes.

I am going to make a couple of suggestions:
1. If you have not had an oil change in the last 6 months, get one. Use only full synthetic oil. One of many reasons to do this is that synthetic oils does not break down as quickly when it sits for a long time. Also, it will keep moving parts coated if they sit a long time. But, the most important is that it helps prevent build up on your intake valves. Oil for our cars should be changed every six months or 7500 miles (Despite what the owners manual says)
2. Have your battery checked to verify that it is good condition. Any auto parts store can test it for you. Our cars make huge electrical demand on the battery. If it sits for long periods of time without trickle charger, that battery can be way down on power. So, when you do get out and drive, the spark plugs may not get full voltage to initiate a good spark which will not properly burn the fuel which in turn makes the engine not run correctly. If you car does sit for long time, I suggest that you get a maintenance/trickle charger for battery maintenance.
3. As mentioned above, good gas is also essential. Gas with ethanol doesn't do well when it sits for a long time and can damage the fuel system. It is hydroscopic (attracts moisture). If your gas in your tank has moisture in it, that will cause loss of power. You can put in good, fresh fuel and add a fuel stabilizer.
4. Not that it is part of your loss of power, but our Fusion Sports are notorious for shipping from the factory without the proper amount of transmission fluid. You definitely want to have that checked. If you check it yourself, the dip stick is located under air filter housing. You have to remove the housing to access the dip stick.
5. Definitely check that air filter and housing. As mentioned above, check for rodents making a nest in the air intake opening and filter box.

Good luck!
 
#14 ·
To add to the post above mine, when changing your oil, DO NOT go by Ford's 10,000 mile oil change interval. The "sensor" in our engines is merely checking against the odometer, and not actually measuring how much "life" is left in the oil. Many modern cars suffer a lot of failures due to oil sludging up over extended durations. I change the oil every 3000 miles/6 months regardless of what the car says.
 
#15 ·
Hi Woodman. The IOLM (Intelligent Oil Life Monitor) in our cars is not "...merely checking against the odometer" (and/or calendar). It also calculates engine run hours versus mileage and other factors into the algorithm/calculations (an indicator of stop and go versus highway miles etc.).
Yes, you are correct that the IOLM does not perform a detailed "Oil Analysis" like a lab such as Blackstone would. But then again, that is overkill and not necessary.

And just to make it clear...I am not making any comment or judgment on how/when you or anyone else wants to perform their oil changes. I am simply providing the correct information concerning the IOLM. As far as I am concerned, we can change our oil every 3 months/3,000 miles (or sooner) or follow the minimum required Ford Maintenance schedule and change at 1 year/10,000 miles ("Normal" vehicle use, sooner if we fit "Severe Duty" service).
As long as an owner at least follows the minimum OCI, in order to protect their Warranty coverage. Everyone is free to change their oil at whatever interval they want otherwise.

However, justto avoid confusion for others...The IOLM is more than an odometer/calendar countdown timer, as I briefly outlined above, and as can be verifed in our Owners Manuals and/or with a brief Google search.

Good luck.
 
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#17 ·
Some other ideas:
The brakes are dragging or emergency brake not fully disengaged​
The membrane in the OEM blow off valve is damaged​
Air leak (air box not fully sealed, loose vacuum hose, loose clamps in intake tract)​
Long term fuel trim needs to be reset​
Clogged catalytic converter or exhaust​
 
#22 · (Edited)
On the spark, I should mention that it's actually a little more complicated in our cars. It used to be that you could just remove the positive battery cable to test a car's battery, that's true. But our cars use a Battery Monitoring System, which means we have a computer which controls the operation of the alternator at all times, among other functions.

The effect of this is that the alternator might not be running even if the car is. Of course, if the battery is low, the alternator should be re-engaged, but just keep in mind that at any time that alternator might not be running. So if you pull the battery cable, the car could just die, even if the alternator is fine.
 
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