Many years later after this conversation, I was Googling because the same thing just happened. I went to the mechanic this morning due to a check engine light on the dash. He checked the code and started by saying that it’s nothing serious but, emissions related. He asked me if I’ve had the gas cap replaced recently. I said, “No, it’s probably the factory installed gas cap.” I have a '99 Mazda. He then said that, first, he would recommend buying a new gas cap from a dealer and bringing it back to them so they can install it. He said if the code doesn’t go away after that, then bring it back and they’ll do a smoke test. The dealer closest to me didn’t have a gas cap in stock so I ordered it and will go back next week so they can install it.
Really no reason to drag up an old thread but you should be able to ‘install a gas cap by yourself’.
Excuse me. Just happy to see information that was the same.
That sounds like good advice your shop gave you there @criley0717 . There’s quite a few things that can cause evap system issues. But the gas cap is a common one, and inexpensive to give a try. It has to seal the tank so fumes can’t get out and cause air pollution, but still allow air to enter the tank as the gas is used up as you drive, to avoid the tank building a vacuum and preventing gas from flowing to the engine. It also has to allow fumes out if the pressure gets too high in the tank, for example if the gas tank gets overheated when the car sits in the full sun on a 110 degree day. It has to do that so the tank doesn’t rupture from over-pressure. So it’s a more complicated gadget than it appears, with one way pressure sensing valves and the main gasket itself can fail.
My Hyundai Elantra is throwing a P0456 code for small eval leak. I was told that a smoke test was necessary after replacing the gas cap didn’t keep the CEL off. Can a smoke test be done if there’s more than half a tank of gas in the fuel tank? I’m being told no. Any thoughts?
Suggest to repost as a new topic @Rebekah_Johnson . You’ll get better results. Click “maintenance/repairs” above left, then “new topic” above right.
He can’t tell you the cost to repair until the smoke test is completed.
yes, using the evap/smoke machine
But . . . if the fuel level is too high, the evap readiness monitor may not run to completion
This is useful information, and is actually what a professional mechanic told me to do in order to get one of my cars through emissions: top off fuel, clear codes, drive long enough so that all monitors except for evaporative emissions set, then top it off again, take car to be inspected.
Here is what I would do if I were in your shoes… AND you didn’t need to get your vehicle inspected any time in the near future. Walk away from the place that is telling you that you need a smoke test that they dont know how much will cost etc…
Then you can pull your engine code and study up on the issue…educate yourself and possibly even repair the problem yourself. Smoke tests have their place but only after a mechanic uses the engine code, his skills. common repair solutions for that vehicle and code and his own experience to rule simple items out at first…maybe even fix the problem. Skipping straight to a smoke test is (imho) a bit premature… I use the smoke when I have run out of simple and common solutions…it is used to find troublesome leaks in the system…if a leak is the problem at hand…
Your issue is a non critical type of problem and shouldn’t effect driveability, so… like I said… leave this place suggesting the smoke … he is currently blowing that smoke… you know where.
Pull your code and study up on the problem…see what you find out.
such as blown fuses, rat-damaged wiring, and so forth 