CarTalk.com Blogs Car Info Our Show Deals Mechanics Files Vehicle Donation

How to replace a vapor canister vent valve

Dear Tom and Ray,
I am about 99.99% sure that the weird ‘trouble’ with my 2001 6cyl 4x4 Xterra is a clogged gas tank vent solenoid, or as it is called now a “Vapor Canister Vent Valve”. For the last 2 or 3 years, very infrequently, the vehicle turns completely off while decelerating (sometimes at very fast speeds so I have learned to be calm and put the car in N and turn the key and keep going with the flow so to speak). It also, either during a stop in idle or accelerating very slowly and steadily, makes popping sounds directly under the left back seat–which is where the gas tank is located. It sounds like the tank (or a metal can if you will) is being sucked in until it gives making the popping/banging sound against the car (underneath). The other issue this problem seems to be linked to is the engine light coming on when the tank pops. I have had that diagnosed too, and it just reads “engine knock sensor”. My previous wonderful mechanic, who moved about 30 states away, is no longer available but he did tell me it sounds like a blocked or clogged gas tank vent solenoid. He also said it’s not a big problem per se, but at some point I should probably replace it. Sometimes there are 6 months that go by with no popping, stalling, or engine light coming on. So maybe ‘bad gasoline’ also plays into this issue?? I did an internet search recently and found a replacement part called a vapor canister vent valve. My question is how easy or hard is this thing to replace? Can it simply be ‘blown out’ with an air hose, or otherwise ‘cleaned’ instead of replacing it (it costs about $80). The only thing scarier for me to fix than home electrical wires would be anything dealing with GAS. Hence, I need your superior advice!
Thanks so much!
Susan

@SusanWhite55, are you sure you didn’t misunderstand your mechanic?

I haven’t seen your car, but if I pulled a knock sensor code, my first instinct would NOT be the vent solenoid.

I would start looking around for your next mechanic/shop at this point.