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

2007 Chevrolet Tahoe - CEL for a few years

My '07 Tahoe for the past few years has had the check engine light on. When I have brought it to my trusted mechanic he says the code reads a small evap. leak and that it is most likely a gas cap. 3 gas caps later and an emissions test rapidly approaching the light still is on and he said you’ll need to get a smoke test but I do not have that equipment here. So I took it to the dealership. They ran the smoke test and they said, “it’s your gas cap.” After I told them that I had changed it out 3 times they told me it was because it was an off brand at the Tahoe was notoriously known to have to use OEM part and that smoke was just pouring out from the gas cap when they ran the test. Well, the new gas cap got me though my emissions test and within a week the light came back on. I took it back to my mechanic who ran the code reader and it was the same code again. What else could it be?

Take a close look at the filler neck. Is it gouged or corroded. That might prevent a good seal.

3 Likes

Would this also be the cause if when I am at the gas pump filling up and I put the lock on the gas pump handle to keep it going by itself until it’s full and it keeps stopping well before the tank is filled?

Paul, that is a classic problem with these vehicles as they age. Time for a new charcoal canister and purge valve. Make sure the tech blows out all the lines and checks the filler neck for corrosion leaks and the lines for cracks and splits.

2 Likes

+1
It’s also time for a new mechanic, as the OP’s guy apparently missed the obvious symptoms for several years.

2 Likes

You’re going to end up with a bushel basket full of fuel caps, if the fuel tank pressure sensor isn’t replaced.

https://www.rockauto.com/en/catalog/chevrolet,2007,tahoe,5.3l+v8,1433255,fuel+&+air,fuel+tank+pressure+sensor,6385

Tester

Changing gas caps by the case is lunacy and really grasping at straws.

Do I read this right? Do you continue to fill the tank after the gas nozzle shuts itself off? That is a no-no. Round it up to the next nickle or dime and stop. Do not continue to force another 2 bucks into it.

1 Like

You can longer PACK a gas tank to where it will flood the EVAP system.

There’s a device in the ORVR system that prevents that.

Tester

I only do it when the tank is pretty much empty and I know it’s going to take about 22 gallons to fill it and then it stops at like 2 gallons and like every other gallon.

Had a problem for years that filling up on fast it would burp out gas at the end, so last 1/ tank or so would fill it on slow and no problem. Had the small evap leak, luckily it came on 1 month after emsission test. Gas cap worked the first time for a couple of years. Got rearended, was looking at repairs and was surprised to hear it is probably a cracked filler neck or the connection on the top of the tank, 600 to 1200 depending. Traded it in and kept the cash for the damage from getting rear ended.

Ok. I have some good take aways. Charcoal canister, purge valve and have the filler neck checked out. Hopefully one of these. Takes care of the problem.

Did you clean the edge of the filler neck where the gas cap gasket contacts it?