Help CEL codes 00 boxster

[tsmith3108]

I have a 2000 boxster 2.7 The CEL came on a while back with P1128/P1130. I have tried everything I know now. I replaced the MAF which was 986.606.125.00 with the latest 986.606.125.01 and took it to a porche place to reset the codes. The CEL stayed off for about 280 miles and then came on again. I then started looking for vacuum leaks as my next option. Went over every hose and connection and found nothing. I reset the CEL and it stayed off for about 1k and then came on again same codes. I went over the whole vacuum thing again and found nothing. I have checked for vaccum in the oil dipstick tube thinking maybe oil separator going bad but nothing there. It has the new style oil separator on it not the original. It seems to be fine until the gas tank starts getting low at around 280-300 miles. Its not when the car is cold so I ruled out the cold start circuit. This last time I was sitting at a light waiting for it to change and bing there goes the light and 286 miles on this tank of gas and showing below a quarter. The car was up to temp and just idling. Is there something in the fuel evap circuit or could a fuel filter going bad cause it to lean out when the fuel is low in the tank? I'm at my wits end. I purchased a cable and software so i can pull the codes and reset the light but it gets old doing it every other tank of gas. Its not consistent at 280 miles either. It only pops on when it feels like it. Sometimes its 600-900 miles between incidents. The O2 sensors seem to track fine according to the software. I did fit a K&N filter before it started doing this nonsense but I clean it every 5k miles and its not clogged and I don't over oil it. Perhaps I should go back to factory but it doesn't seem logical to blame that.

Anyone out there with any ideas on where else I can look or where I should focus coz I'm missing something obviously.

I'm liking my '77 911s and its simplicity more and more every day. If only the Air conditioning could keep up with the Texas heat.

Anyone. Any ideas. anything I missed?

Edited June 8, 2008 by tsmith3108

[Chris_in_NH]

vacuum leaks could be occuring via cracks in the oil filler tube or AOS bellows tube. just a thought...

how many miles are on the car? has the fuel filter ever been changed?

but i think K&Ns are notorious for setting off this code. switch back to the OEM filter and see what happens. as you said, it didn't start until you switched filters. last thing touched... ;)

btw, there is a TON of info on these codes here. i'm guessing that's why no-one besides me has responded. just search this forum for '1128 1130'. also search for 'K&N' to learn more about others' experiences with those filters.

[tsmith3108]

vacuum leaks could be occuring via cracks in the oil filler tube or AOS bellows tube. just a thought...

how many miles are on the car? has the fuel filter ever been changed?

but i think K&Ns are notorious for setting off this code. switch back to the OEM filter and see what happens. as you said, it didn't start until you switched filters. last thing touched... ;)

btw, there is a TON of info on these codes here. i'm guessing that's why no-one besides me has responded. just search this forum for '1128 1130'. also search for 'K&N' to learn more about others' experiences with those filters.

Thanks for the reply Chris - I did search the forums on the codes thats where I got all the great info to check all the things I did and these forums are awesome.

BTW 82k on the car and no I have not changed the fuel filter in last 15k.

Next on my list is put in new factory air filter and change fuel filter and i'll throw in a set of plugs for good measure as its been at least 15k since last set and see what that does.

[Topless]

Someone on this board replaced a bad gas cap and solved these codes. Give it a look.

[Chris_in_NH]

Thanks for the reply Chris - I did search the forums on the codes thats where I got all the great info to check all the things I did and these forums are awesome.

BTW 82k on the car and no I have not changed the fuel filter in last 15k.

Next on my list is put in new factory air filter and change fuel filter and i'll throw in a set of plugs for good measure as its been at least 15k since last set and see what that does.

i would do one at a time. change back to the OEM filter and see if the codes go away. if they don't, you'll know it's not the K&N and you may want to go ahead and use it if it's not causing the codes (although i really think it is). but if you change both the fuel filter and air filter at the same time and the codes go away, you won't really know which one it was! :huh:

and again, you said these codes started after you went to the K&N... ;)

Someone on this board replaced a bad gas cap and solved these codes. Give it a look.

yes a bad gas/oil/coolant cap can cause these codes. when you (or we in my state) get emissions tested, the gas cap is checked on some kind of gas-cap-checking device. i'm not sure if they do that everywhere in the US.

[tsmith3108]

Thanks for the reply Chris - I did search the forums on the codes thats where I got all the great info to check all the things I did and these forums are awesome.

BTW 82k on the car and no I have not changed the fuel filter in last 15k.

Next on my list is put in new factory air filter and change fuel filter and i'll throw in a set of plugs for good measure as its been at least 15k since last set and see what that does.

i would do one at a time. change back to the OEM filter and see if the codes go away. if they don't, you'll know it's not the K&N and you may want to go ahead and use it if it's not causing the codes (although i really think it is). but if you change both the fuel filter and air filter at the same time and the codes go away, you won't really know which one it was! :huh:

and again, you said these codes started after you went to the K&N... ;)

Someone on this board replaced a bad gas cap and solved these codes. Give it a look.

yes a bad gas/oil/coolant cap can cause these codes. when you (or we in my state) get emissions tested, the gas cap is checked on some kind of gas-cap-checking device. i'm not sure if they do that everywhere in the US.

[tsmith3108]

Thanks chris for the suggestions to tackle them one at a time as that makes perfect sense. The new parts arrived today but I will follow that wisdom. (driving my '77 911 today so will tackle the first change tomorrow.

I like the bad gas cap idea too because it never triggers the CEL till the tank is below 1/4 full which is also wierd but I would not have thought a bad gas cap could trigger a lean condition unless Porsche uses that code for multiple emissions related errors.

[dezpimpdada]

i was having CEL p1128/1130 and took the car to a smog shop to test the cap. it passed but the cap has many cracks on the inside. the tech says sometimes it may pass the test however it doesn't always guarantee that it is holding pressure to the factory standard.

i am getting a new one even thougth my problem was caused by a bad AOS.

Cheers!