Random check engine light
 

I know this is a shot in the dark, but wanted to ask anyways.

I have a 2003 Boxster S and today while sitting in the drive through of in n out the check engine light came on. Car has been running perfect and still runs perfect. Any idea on what it may possibly be.

Also, I know my brother has a generic OBC II scanner, can I just plug that in and it will give me a code I can look up?

Thanks.

In-N-Out Burger! What did you get a double-double with cheese?

The CEL could be one of many things, you need to get it scanned. The OBC II should work.

Yes, the CEL comes on when something is not right with the car. Scan for error codes and write them down. Most problems are an easy fix once you know what to look for.

So the code that came up was P0440 - Evaporative Emission system...

I did a search but didn't really come up with a fix. Thoughts?

And yes, I have opened and reclosed/rechecked my gas cap...

Troubleshooting guide:
OBD II Code P0440

Yes, if you open your gas cap and look closely at the sealing o-ring. Sometimes these get cracks in them and no longer seal completely, causing the evap sys to be unable to pull a vacuum on your gas tank. This will trip a P0440. A crappy aftermarket gas cap will cause this as well. Make sure it is a Porsche OEM gas cap.

Good hunting!

Thanks for link and tip on checking the o-ring seal.

I was having the same issue. Found the air oil seperator needed to be replaced. No cel since .

So i wanted to update everyone and also look further into this problem because I don't think I fully 'fixed' it yet.

As I mentioned in my previous post the code which showed up when I plugged in the obcii reader was P0440 - Evaporative Emission system... I cleared the code and it never came back. It's been almost a week now and still no code. I checked the seal on the gas cap and it looks good. The car seems to idle a bit rough at idle, around a 50-100rpm fluctuation. But my main concern is my gas mileage, it's gone to crap, i've lost about 4-5 mpg.

Around the city i'm getting about 15.5 mpg which is really low compared to what i normally get for the same driving. For highway, i'm geting about 18-19, again, about 4-5 mpg lower than usual.

I have an 03 Boxster S.

Any ideas on why my gas milage has gone to crap?

I know a dirty throttle body can cause a rough idle, but can it make my gas mileage go to crap??

When was the last time you took apart the TB? Well, as they say, that's too long!

When you take apart the Throttle Body you will see WHY your gas mileage has taken a nose dive. From the butterfly valve back there is all kinds of dust, dirt & grime. I have resorted to doing mine every 3 months but it is a daily driver.

The process is pretty easy but wear gloves or your hands will be mangled!

Don't panic too if it takes a while, a few curse words, and a LOT of WIGGLING to get it back together. Is it worth it? You have a dead level idle and the acceleration is through the roof. Something that is a MUST before a track day.

Good luck!

Can't wait to tackle the throttle body this weekend! Would you just use carb cleaner or something else? I read somewhere that carb cleaner might be too strong? Thanks again for info.