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How do I fix a vacum leak on 2002 nissam sentra gxe

I had a check engine light test run and came up with code #490 large vacume leakand fuel system fault

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  • Rev. Michael Fowler Dec 04, 2012

    Thank you for the help, still trying to find leak, all of a sudden the heater does not want to heat air? any ideas.

  • Rev. Michael Fowler Dec 04, 2012

    I also had the oil dip stick handle brak apart and no cannot get dip stick out of tube it keeps goin futher down into tube

  • montehammons Dec 04, 2012

    The dipstick tube can be removed to retrieve the broken stick. Will either be held on by a bolt through a bracket at the base of the tube, or it will just be pressed into the block-grab it and yank it out, if no bolt needs removing.

  • montehammons Dec 04, 2012

    Does the heater fan still blow? If the heater core is still circulating coolant and the fan still blows, then no heat coming out is probably caused by the heater cases' doors not operating properly. To check the core's circulation, the car must be at normal operating temperature, and running, with the heater controls on high heat setting. Under the hood on the firewall, the inlet and outlet hoses for the heater core are visible. You just feel both hoses. Both should be hot, telling you the heater core is circulating coolant. the core circulates fluid, the heater fan blows air across the core's surface, and heated air comes out the vents. that how its supposed to work.

  • montehammons Dec 04, 2012

    And if still no leak found, no obvious signs, by the way, how does it run, both at idle and off-idle? Is it running rough, or have a continuous surging? You may want a little more extensive testing done by a shop, if you're not a dedicated do-it-yourselfer. You might, might I say, be looking at replacing some gaskets, like the intake manifold gasket. Hard to say from here, it's a hands on job and right now you are the only hands there. I wish you luck from the comfort of a warm house on a cold night in montana.

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  • Cars & Trucks Master
  • 5,252 Answers

You have to find the leak and seal it up, hey. It may help to picture where vacuum originates in the engine: As the pistons move down in the cylinders they pull air in from the intake manifold. This creates a pressure drop in the intake, a vacuum that is maintained as the engine is running. New air that is pulled into the intake is measured by the Mass Air Flow sensor mounted in the big boot between the air filter and the intake. If extra air is pulled into the intake manifold from a vacuum leak, uncalibrated air, the computer can figure it out from the oxygen sensors reading in the exhaust-mixture is too lean, so the computer will try to compensate by delivering more fuel, but can't deliver enough, mix is still too lean, so computer sets a code for the vacuum leak.
The intake will have a few vacuum taps with hoses running to engine or car controls that require vacuum to operate. If one of the hoses comes off or has a leak, that is extra air into the intake. Your power brake booster has a large vacuum tap. That may be the problem. With the engine running, pull off that line and plug it, and see if engine speed changes. If the idle drops that may be your leak-a failed power brake booster.
If nothing yet, keep engine running and spray some starting fluid around the mounting area of the intake manifold (maybe the intake gasket has failed and sprung a leak) and listen for a change in engine pitch or speed. The fluid may get sucked into the intake and cause speed to change. If it does, you would need to remove the intake manifold and fit a new manifold gasket.
Also check the big boot from the air filter to the throttle body for tears or loose fit. Good luck, Rev!

Posted on Nov 30, 2012

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Posted on Jan 02, 2017

emissionwiz
  • 75051 Answers

SOURCE: Check valve missing in fuel tank filler neck.

P1444 Purge Flow Sensor Circuit Input Low 0
The evaporative emission control system checks to make sure there are no leaks in the lines that run from the gas tank to the charcoal canister and up to the engine. It also checks to make sure the gas cap is sealing correctly.
When you fill your car with gas, the vapors in the tank get forced into a canister filled with activated charcoal. Also, on a hot day as the gas heats up and vaporizes, those same vapors push into the canister where they're stored. But the charcoal can only hold so much vapor. At some point it has to be emptied. The emptying process is called "canister purge." Here's how it works.
The computer orders a canister purge by powering open a PURGE solenoid. That opens the vacuum line between the canister and the intake manifold. At the same time, it opens a VENT solenoid. That allows fresh air into the canister. So the engine is literally sucking out the gas vapors and purging the canister with fresh air. The computer has to adapt its fuel strategy to take advantage of all the extra gas vapors coming into the engine.
The computer notices the canister is empty when it detects a leaner condition (all the vapors are used up) and it resumes normal fuel delivery. Some car manufacturers then close the VENT solenoid but leave the PURGE solenoid open. That creates a vacuum throughout the entire fuel storage system. Once the correct vacuum is reached, it closed the PURGE solenoid and waits to see if the vacuum holds. If it doesn, the system passes the test. If it detects a leak, it sets a code.
In this code P1444, the computer sees a lower than expected value on the purge flow sensor. bottom line? replace the purge flow sensor.

Posted on Sep 03, 2009

  • 538 Answers

SOURCE: 1999 mazda 626 4cyl runs rough at idle , engine

You may have to dig deeper for a vacuum leak. It's possibly the intake manifold gasket. Try spraying some starting fluid around the intake manifold. Also try disconnecting the brake booster and plugging that hose, the diaphram in the booster could be ruptured, causing a vacuum leak. Check the PCV valve and hose too.

Posted on Mar 06, 2010

  • 125 Answers

SOURCE: 88 Toy, 22R Carb, hard cold start

in your carburetor there is a priming passage. look in there with the air cleaner out and pump the butterfly it should squirt gas. if it doesn't then you need to open the top part of the carb and clean the hole with a hair clip. if this is not the problem it will be the choke but I'm 70 percent that this is the problem.

Posted on May 25, 2009

  • 383 Answers

SOURCE: ck engine light , p1107 code reading ,cant find any vacum leak? olds 88 96 model 3.8 liter.

a3342: Your code is for map sensor intermittent low voltage.
This car has on board diagnostic capabilities which is what AllDATA recommends doing first.

Posted on Apr 24, 2009

  • 67 Answers

SOURCE: saturn code p0442, evap system small leak, can't find leak

I would send the car in for a smoke test...So much easier to find the leak...

Posted on Mar 16, 2010

Testimonial: "found another definitation for a code 422. replaced rear o2,fixed"

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