Low power, low barometer pressure reading Nissan Sentra 2008

Nissan Sentra 2008
I have sluggish acceleration; I am reading 13.78 psi instead of 14.25psi.
I used to read 14.25psi; but I dont know what happened that I am reading that now. But the same car in good working condition reads 14.25 psi.
Nissan use evap pressure sensor installed on the charcoal canister; and this give the reading to the barometer pressure reading.
How do I know this cause the sluggish acceleration? I disconnected the sensor and drive; the car was like snail and bad/ worse acceleration but when I connected back. I had the little power back.

What done so far.
-Removed charcoal canister and check for damage; no visible damage and air passage between the fuel tank hose port and the purge port has free airflow.Took the time to service it as well.
-Checked purge solenoid valve sensor; all good. Close tight without leaking air.
-Checked fuel cap; not damaged or in bad condition
-Replacement of the evap pressure sensor; but reading didnt change.

Please any idea, where I should go or check to solve this problem.

The attached picture shows the overview of the charcoal canister where the evap pressure is located. In the diagram is the number 10

No pix.
You could try a variable resistor while watching the scan tool to bring the baro into normal range and take it for a drive.

Mariowinax1 wrote:

Nissan Sentra 2008
I have sluggish acceleration; I am reading 13.78 psi instead of 14.25psi.
I used to read 14.25psi; but I dont know what happened that I am reading that now. But the same car in good working condition reads 14.25 psi.
Nissan use evap pressure sensor installed on the charcoal canister; and this give the reading to the barometer pressure reading.

You could measure the pressure in there with an independent Gauge !!

Can you remove all the pipe work from the canister to see if you get correct reading of atmospheric pressure.

Does the lower pressure, if correct and validated, not indicate a blockage downstream of the Baro ? Just asking !

Noah wrote:

No pix.
You could try a variable resistor while watching the scan tool to bring the baro into normal range and take it for a drive.

Please how do I do that, a video sample to show that?
Or direction

Mariowinax1 wrote:

Noah wrote:

No pix.
You could try a variable resistor while watching the scan tool to bring the baro into normal range and take it for a drive.

Please how do I do that, a video sample to show that?
Or direction

This is the picture attached

George Uk wrote:

Mariowinax1 wrote:

Nissan Sentra 2008
I have sluggish acceleration; I am reading 13.78 psi instead of 14.25psi.
I used to read 14.25psi; but I dont know what happened that I am reading that now. But the same car in good working condition reads 14.25 psi.
Nissan use evap pressure sensor installed on the charcoal canister; and this give the reading to the barometer pressure reading.

You could measure the pressure in there with an independent Gauge !!

Can you remove all the pipe work from the canister to see if you get correct reading of atmospheric pressure.

Does the lower pressure, if correct and validated, not indicate a blockage downstream of the Baro ? Just asking !

Sample of independent gauge that I can use, picture or video of it?
When i dropped the canister I took time off to check all; there are three hoses that goes to it.
One is the big fuel tank hose, purge hose to engine intake, and vent hose to air, and they were all in good shape.
Check the attached picture.

Btw, when I unplug the evap sensor while connected to the harness and close the opening of the sensor to the canister with my thumb so that no air goes to it; monitoring scan tool.
I see pressure rise to 14.25psi but when I insert it back to the canister barometer pressure drops again.

[/quote] Sample of independent gauge that I can use, picture or video of it?
[/quote]

2 pictures attached for you ?
1. Sealey Vacuum / Pressure Gauge - Simple but really good.
2. Mityvac - As the Sealey but you can create Vacuum & Pressure to test components and reactions - Again - Really good essential tool to have.

When i dropped the canister I took time off to check all; there are three hoses that goes to it.
One is the big fuel tank hose, purge hose to engine intake, and vent hose to air, and they were all in good shape.

Been a while since I had the pleasure of an EVAP fault,

Your vent hose to air in my mind cannot be straight to atmosphere, that would defeat the theory of a Sealed System !!

There must be some sort of controlled solenoid / valve between the canister and atmosphere - indeed that may be part of the canister or external !!

Does it work ?
Is it Blocked Shut ? Jammed open even slightly ?
Can it be activated ? Able to fully seal and open ?

Then we have the valve that purges fumes from the Canister to the Inlet. Same again

Does it work ?
Is it Blocked Shut ? Jammed open even slightly ?
Can it be activated ? Able to fully seal and open ?

You say you have checked the pipe work however there maybe more valves etc around or internal to the fuel tank. Including the Tank Shut off Valve and the pipework to the Filler cap area.

As a refresher, I went to "Google" and "Youtube" to refresh my knowledge on EVAP, its purpose and function.

In your shoes I would now be looking to find, evaluate & test every component in that system to establish how and why you have a lower pressure than you should.

A trapped, collapsed hose maybe ??

I have sluggish acceleration; I am reading 13.78 psi instead of 14.25psi.

Could some one drop in here and advise if 0.47 psi error be enough to cause that sluggish acceleration

What is the reading when trying to accelerate under load on the road ??

Sorry for the Vague post but I'm trying to help yet learn myself

I would not sweat about the baro reading, the difference is less than 5%. I consider this tolerable/not significant.

Ok, Noted
So should chase other areas for the low power and MPG right.
Thanks guys for helping to fix it.