fast1

I was just wondering if any other Boxster owner has this problem: if I allow the fuel tank to run low enough to trigger the add fuel reminder, I get a CEL code indicating that I have an emission leak. Of course as soon as I fill the tank and clear the code, the CEL does not return, as long as I don't allow the gas tank to run low.
Any theories?

No HTwo O

New gas cap needed??

fast1

Yep. I was thinking the same thing, but why would the problem only occur when the gas tank is low. If the gas cap is bad, wouldn't the emission leak be constant?

Barn996

Post the code if you have a code reader.

No HTwo O

Less head space when full?? What about the carbon canister?

Macster

As someone else wisely suggested: Post the code.

My 02 or 03 cars do not do this.

Too many other owners run the fuel level down low enough the low fuel warning light comes on and yet do not report seeing the CEL lit for this to be an overlooked 'feature' of newer MY cars.

Post the code.

Sincerely,

Macster.

fast1

I'll have to wait until it recurs. I cleared it and don't recall the code. Anyway it only happened 2 times in the last 18 months so it's no big deal.

fast1

One last point. The first time I got the CEL, about 18 months ago, I took it to the Dealer since it was scheduled for a routine maintenance. The Porsche tech told me that the code was triggered because I allowed my fuel tank to fall below 2 gallons. Didn't realize that would trigger a CEL code.

No HTwo O

That's bullsheet. Don't go back to that dealership. Find a trusted indy shop in your area.

fast1

These emission faults are a pain. Since the problem is so intermitten, I expect that it's a faulty reading and I'm not going to obsess about it. In MD you are required to have your car tested for emissions every two years, and my car was tested about a month ago with no problem.

Macster

No HTwo 0 put it a might strong, but I'm inclined to agree with the opinion.

All I really have experience with is my cars, an 02 Boxster (base) and an 03 Turbo.

The lowest I've run the Boxster's tank down is just recently when upon fillup the tank took 15.66 gallons (and cost me over $60!) to fil. While the low fuel level warning light was on -- and for a while I might add -- the CEL was not on, never came on.

I've run the tank to the low fuel level warning light level many times and never have I seen the CEL come on and produce that code. (Rarely, the CEL does come on but the error code points to a weak converter. The CEL coming on during low fuel level is just a coincidence.)

Futhermore, if what the mechanic told you was true, I have to believe we would have had a post similar to your's before now, and I can't remember ever reading one.

My WAG is the gas cap is leaking. This agrees with a few others who've posted the same opinion.

But next time -- anytime! -- you go to the trouble of reading a code always write it down. The next time post the code and that will provide a clue as to what's going on.

In the meantime, check the gas cap and its seal (o-ring I think) for any signs of a nick or crack or roughness or even a bit of dirt. Check the filler tube end where the cap fits for anything on the surface that might result in less than a pressure/vacuum seal.

And every time you fill up the tank, pay particular attention to ensuring you put the cap on correctly and tighten it appropriately.

Sincerely,

Macster.

sak_27

I have had a similar problem recently. My last two fill ups have been when the low fuel warning light has been on. Shortly after filling up, my check engine light turns on. After driving for a few days the light turns off. At this point I'm tempted to buy a new gas cap and see if the problem still occurs.

sak
'99 Boxster
78k miles

Bought the car used 2 months ago.

logray

Next time the code is on stop by an autozone, oreilly, pep boys, etc. They will read the codes for free and you can post them here.

sak_27

Just an update. I recently bought a new gas cap and replaced my old one. I have also stopped pumping gas beyond the gas pumps automatic shut off. Since then I have not experienced a CEL. It has been two fill ups and counting. If the CEL comes back on, I will definitely get the code read and post it.

thanks

Macster

Thanks for the update. And just to reinforce this, do not/avoid filling up the gas tank past the point the nozzle shut off trips.

This assumes of course the nozzle shut off doesn't trip prematurely. With my Boxster I have not found this to be a problem. With my Turbo the same nozzles that work just fine with the Boxster sometimes prematurely trip when I'm filling the Turbo's tank. What I have found works for me is to rotate the nozzle handle to the 9 o'clock position -- the handle is pointing towards the rear of the car -- and then squeeze the nozzle handle, even use the handle lock. When the nozzle shuts off the tank is properly filled. In fact this method appears to result in quite consistent fillups of the Turbo.

Sincerely,

Macster.