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2016 Frontier SV 2WD
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Discussion Starter · #1 · (Edited)
I ran a test on my 2016 and found my long-term-fuel-trim is 10.16%. Truck has 130K miles and I recently changed the plenum gasket and spark plugs. After seeing this number I ran a test on my 2016 Sonata(51k miles) and long-term-fuel-trim was 0%. I was looking at the short-term-fuel-trim on a graph and did not see a nice graph oscillating between + and - values.

Is this 10.16% is normal for Frontier's?
If it's not what can I do to bring it close to 0%.
I get about 18mpg on highways and never got 23 mpg as advertised.
I bought the truck when it had 120k miles and I have used fuel injector cleaners every 5k miles.
Check-engine light was on recently and the error was fuel-system-lean and went away after changing the spark plugs and the plenum gasket which was really bad.
Right now the truck is running as expected without any issues.
 

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Here's a few places to check for vacuum leaks:
Dipstick top seal,
Oil fill cap Oring,
Cracked bellows on air intake tube,
Cracked plastic intake tube,
Air intake hose clamps,
Vent hose from left valve cover to air intake,
Valve cover to valve cover crossover hose,
Power brake hose,
PCV valve and Oring,
PCV hose ?
Injector O-rings...
There can't be any air leaks between the maf and the cylinder head.

MAF is dirty or bad.
O2 sensors are going out. (the ones closest to the engine.)

If you pulled the manifold to change the plugs, are you confident the gaskets are in place?
If you need hoses, you gotta read THIS.
 

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2016 Frontier SV 2WD
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Discussion Starter · #3 ·
Here's a few places to check for vacuum leaks:
Dipstick top seal,
Oil fill cap Oring,
Cracked bellows on air intake tube,
Cracked plastic intake tube,
Air intake hose clamps,
Vent hose from left valve cover to air intake,
Valve cover to valve cover crossover hose,
Power brake hose,
PCV valve and Oring,
PCV hose ?
Injector O-rings...
There can't be any air leaks between the maf and the cylinder head.

MAF is dirty or bad.
O2 sensors are going out. (the ones closest to the engine.)

If you pulled the manifold to change the plugs, are you confident the gaskets are in place?
If you need hoses, you gotta read THIS.
I used Nissan OEM gaskets and I am pretty sure they are in place. If there is a vacuum leak shouldn't I get an error code?
 

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I used Nissan OEM gaskets and I am pretty sure they are in place. If there is a vacuum leak shouldn't I get an error code?
Yes you should be getting some error codes. But your LT fuel trim is way too high.

The definitive method to detect leaks is the smoke test. Not too expensive. But only mechanics have the equipment.

It could be an upstream O2 sensor. If you have the time, I would swap bank 1 for bank 2 and see if the problem moves with the change.
 

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Discussion Starter · #5 ·
Before I start changing parts can someone please take a look at the following attached files and check if it is possible to figure out what is going on with my truck? I look at some data and realized the actual mpg is about 13. After driving 30miles LTFT went up. On the first report it was 10.16 on both sides and after driving about 30miles it went to 14.84/11.72.

OBD2_1.pdf - this is a diagnostic report generated on 9/17
OBD_2.pdf - second diagnostic report generated on 9/19 after driving about 30miles since 9/17.
OS_1.png - Oxygen sensor graph that i found on the OBD2 scanning software and not sure what it means.
OS_2.png - this is the voltage/time graph of the upstream Oxygen sensors. Orange line is bank 1 and Purple one is bank 2 (for some reason it shows up as sensor 5)
PID_Stats.png - Some stats that was able to capture when the vehicle was idling
 

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Follow this procedure to reset the mixture ratio self-learn settings:

1. Start engine and warm it up to normal operating temperature.
2. Turn ignition switch OFF.
3. Disconnect mass air flow sensor harness connector.
4. Restart engine and let it idle for at least 5 seconds.
5. Stop engine and reconnect mass air flow sensor harness connector.
6. On your scanner, check that DTC P0102 is detected.
7. Erase the DTC P0102

Go for a drive, see if the numbers improve.
 

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It seems to me
Before I start changing parts can someone please take a look at the following attached files and check if it is possible to figure out what is going on with my truck? I look at some data and realized the actual mpg is about 13. After driving 30miles LTFT went up. On the first report it was 10.16 on both sides and after driving about 30miles it went to 14.84/11.72.

OBD2_1.pdf - this is a diagnostic report generated on 9/17
OBD_2.pdf - second diagnostic report generated on 9/19 after driving about 30miles since 9/17.
OS_1.png - Oxygen sensor graph that i found on the OBD2 scanning software and not sure what it means.
OS_2.png - this is the voltage/time graph of the upstream Oxygen sensors. Orange line is bank 1 and Purple one is bank 2 (for some reason it shows up as sensor 5)
PID_Stats.png - Some stats that was able to capture when the vehicle was idling
It seems to me that your intake air temperature is way too high and all over the map. The ECM uses air temperature to compute molar (amount counted as discrete molecules) O2 flowrate. An error here will cause fuel trims to be high. I think the air flow temperature sensor is a combined unit with the MAF.
 

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You are looking for a problem where there is none. Your engine is running just fine. You can't get an accurate MPG calculation from a 30 mile trip, not sure how you did your calculation either.

In your ECM/PCM is a chart of expected values for fuel trim. It is a chart of theoretical values of the pulse width that the ECM should be sending to the injectors for the conditions that are being measured. If the actual pulse width, based on feedback from the O2 sensors which keeps the A/F ratio at ideal, varies from the chart, the percentage of that variation is recorded as the fuel trim.

The ECM only see the pulse width supplied to the injector. If the actual fuel pressure regulator is higher or lower than specified, then the pulse width will be shorter or longer respectively. If there is unaccounted air getting into the system, the pulse width must be adjusted accordingly, same if the MAF is slightly off in its measurement. There are many other factors that can affect the pulse width and variations from the chart are expected. When the actual deviation is more than 20%, then a DTC is stored and if you get two in a row, the CEL comes on.

Until then, you have nothing to worry about and do not compare the fuel trim from one vehicle to another. It will drive you crazy if you do. Your system is doing its job.

One more thing, if you have an automatic transmission, you will never get the advertised MPG. If you have a manual, you can actually beat the EPA mileage, especially the city value. My 1997 Hardbody with a 5 speed was rated 20/25. I got 25 on the highway but actually got 25.5 in the big city. I got good at timing the lights so I could maintain a steady speed with few stops. Since my average speed was lower and pretty consistent, it beat the highway value.
 

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Discussion Starter · #11 ·
You are looking for a problem where there is none. Your engine is running just fine. You can't get an accurate MPG calculation from a 30 mile trip, not sure how you did your calculation either.

In your ECM/PCM is a chart of expected values for fuel trim. It is a chart of theoretical values of the pulse width that the ECM should be sending to the injectors for the conditions that are being measured. If the actual pulse width, based on feedback from the O2 sensors which keeps the A/F ratio at ideal, varies from the chart, the percentage of that variation is recorded as the fuel trim.

The ECM only see the pulse width supplied to the injector. If the actual fuel pressure regulator is higher or lower than specified, then the pulse width will be shorter or longer respectively. If there is unaccounted air getting into the system, the pulse width must be adjusted accordingly, same if the MAF is slightly off in its measurement. There are many other factors that can affect the pulse width and variations from the chart are expected. When the actual deviation is more than 20%, then a DTC is stored and if you get two in a row, the CEL comes on.

Until then, you have nothing to worry about and do not compare the fuel trim from one vehicle to another. It will drive you crazy if you do. Your system is doing its job.

One more thing, if you have an automatic transmission, you will never get the advertised MPG. If you have a manual, you can actually beat the EPA mileage, especially the city value. My 1997 Hardbody with a 5 speed was rated 20/25. I got 25 on the highway but actually got 25.5 in the big city. I got good at timing the lights so I could maintain a steady speed with few stops. Since my average speed was lower and pretty consistent, it beat the highway value.
What about the intake air temp? its 55C(131F). I will clean the MAF and check again.
 

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What about the intake air temp? its 55C(131F). I will clean the MAF and check again.
Monitor it while you are driving. I assume you have the stock airbox? Idling on a hot day or in stop and go traffic it could hit that hot, but when moving at a steady speed, especially on the highway, my IAT is usually within 10F of ambient.
 

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Discussion Starter · #13 ·
I think the truck is working as expected now. This is what I did:

Cleaned the MAF - used MAF cleaning fluid from Autozone.
Did what RamTest suggested. Got the error code P0102 and cleared it.
Took it for a ride - about 12miles on a highway.

Here are the results:
Yesterday mpg was 13 and now it's 18 - got it from the OBD2 tool
Intake temperature is good now - 51C (124F) - It was 93F in North Houston.
LTFT has come down to 6.25/8.59. I think it will go down further.

I will check the LTFT after some time and I am sure it will get close to zero.

Thanks everyone for your input!
 

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Discussion Starter · #14 ·
Monitor it while you are driving. I assume you have the stock airbox? Idling on a hot day or in stop and go traffic it could hit that hot, but when moving at a steady speed, especially on the highway, my IAT is usually within 10F of ambient.
I was monitoring the temp while driving and it was fluctuating between 98-140F. Ambient temp was 93F. I do have the stock airbox.
 

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I think the truck is working as expected now. This is what I did:
Cleaned the MAF - used MAF cleaning fluid from Autozone.
Did what RamTest suggested. Got the error code P0102 and cleared it.
Took it for a ride - about 12miles on a highway.

Here are the results:
Yesterday mpg was 13 and now it's 18 - got it from the OBD2 tool
Intake temperature is good now - 51C (124F) - It was 93F in North Houston.
LTFT has come down to 6.25/8.59. I think it will go down further.
I will check the LTFT after some time and I am sure it will get close to zero.
Your STFT is now rich. These numbers are perfectly fine, but it looks like you're shooting for "0" so try this:
Put in a can of this stuff to 1/2 tank of gas, and beat it like a rental:
Berrymans B-12 Chemtool
Best stuff out there for pesky injectors.
At your favorite Walmart. Four bucks a can.
Most parts stores have it also, for a bit more $$.
 

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Got 98-100 while driving and when I stopped the vehicle it goes to 140.
I seriously doubt the 140 °F reading for idle. There is just not enough room between the air entrance and the MAF to heat the air by 40 °F. The MAF is a hot wire anemometer. The HWA has very tiny wires that are heated. I doubt said heating is enough to affect the air temperature.

With the truck at hiway speeds, I would put the tranny in neutral and take the foot off the gas. See how the inlet air temperature reacts. There should be little or no change.
 

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Just remember this, "If it ain't broke, keep fixing it until it is" Red Green.
His other saying about this "If it ain't broke, you haven't fixed it enough".
Maybe not "broke", but it is "off-center." Something is causing a compensating adjustment to be made.
For some folks, it must be dead nuts all the time. For others, close enough is good enough.

Your wheel alignment has an allowable range. Do you want yours aligned at the very edge of that range, or do you want it dead center?
Same deal here. Some would call it fine tuning.
 
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