replacement fuel tank cap - please help

The dealership will have the best cap you can get. Any auto parts store should carry a cap that does the job that it is intended to do, and do it as well as the cap that came on the car from the factory.

Perhaps the better question is, why do you need a "quality" cap? What's the problem that you seek to solve?

If your Check Engine light is on, have you pulled codes to determine what the malfunction is, or do you assume the trouble is the gas cap? There are literally hundreds of ailments that your car can suffer that will cause the check engine light to be on. Three of four of them relate to leaks that can be the gas cap -- leaks that cause the fuel system to not maintain a seal, the gas cap being among the reasons the seal is not maintained -- and a few more are electrical faults related to the fuel system, but that leaves hundreds more faults that have nothing to do with the gas cap.

If the Check Engine light is on, you must pull codes before your wallet runs dry making trips to the parts stores buying all of the gas caps in town.

I was told that the SMOG test failed due to bad gas cap seal but "no" Check Engine light came on. Can that be? I called Lexus dealership, who says that the gas cap should be good if "no" Check Engine light comes on. Hmmm ...

I cannot explain how a gas cap could fail smog AND not triggger the CEL. I cannot explain why it would be tested for smog in your car because the Evaporative Emissions Control System tests it continually. My car is a '94 BMW, the cap is not a monitored part of the emission system so the smog shop tests it separately. I have a '97 F150, and the smog shop (the same smog shop, by the way) does not test the cap because the system monitors it continuously and a code is set if there is a problem. Your Lexus has the same level of emission control as my F150, which is greater than the level in my '94 BMW.

I'm not sure where the 945xx ZIP code is, but it sounds like Calif. Since you failed a test that the car performs all of the time all by itself, and your car does not fail its own tests but fails the State test, I think I'd be calling the BAR (Bureau of Automotive Repair) that is on the smog report.

Me thinks the smog shop runs a gas cap factory on the side, and they want you to buy stuff from them.

Thanks (Jeff), your explanation is very helpful. And, your last sentence is precisely what I was afraid of.

It doesn't make sense, that's fer sure. Assuming it's an OBD II car, which I'm fairly sure a 99 is.. I know when I get mine tested, the car itself is the one that passes itself, or fails itself. They just slap their computer up to it to get the pass/fail data. I forgot how they actually tested the gas cap on my older cars that did the sniff test.. I've had that test on an older Honda, but being as the cap never failed on mine, I never paid too much attention to it.

But if a OBD II car has a bad cap, it should be showing a CEL, and if you scanned the puter, it should show a evap code error of some sort. If no CEL, and no codes are shown, the car thinks the gas cap is fine.

My MIL came on and I took it to AutoZone (I would do that with your car, BTW) and the code came up EVAP.

I had been having trouble with the gas cap, its a "snap on" type. The gasket had gotten turned inside-out...? I turned it right side out and the cap sealed.

Take a look, and check the gasket. Just put the cigarette out first.

But, Hachi, he's not having any known trouble, there is no code.

He went for a smog test, and the test station checked the cap separately from the rest of the car, and the test failed. The car was happy with the cap before the test station came into the picture.

Something smells funny...and it DON'T smell like gas!

Gas caps have been setting off the MIL since ODB-II, for Toyota that was

1995. THis is a '99 Lexus? I didn't tighten the cap on my '95 Tercel once and it set off the MIL.

It's the "smog" caused by the bad gas cap. ;-)

Remove the cap, shove in a screwed up bit of rag, take it back to the "testing" people and stand next to it with that lit cigarette and ask them "Is it OK now?". ;-)

Your mother in law light?

Damn, those Lexus cars are fancy.

They charge $32+ for the factory gas cap. Elsewhere, the non-factory Stant gas cap costs only $6+. Granted, the factory gas cap may be of a better quality but costs 5 times more?

Also, they told me that a minor service should be done every 6,000 miles.

You should spring for the optional Mother In Law Ejector Seat as well. ;-)

:D