my car throws a code P0171 ( fuel system lean bank 1). it comes and goes. stays on for a day or 2 then gone, and will pop up again after a week .
if i bring it in for warranty. they going to say the plenum spacer is causing it. anyone else have this code before

 

The spacer might be the reason you are getting it.

 

Generally this means your o2 sensor in that bank is reading more oxygen than normal in the exhaust. I'd guess you have an air leak after the airflow meter. It could be in your intake tube, or it could be around your manifold spacer. How is your idle? When did it start? (after a modification) Ever get a bank 2 code?

 

it idles fine. i cleared the code last night and this time it came right back after driving around the block.. going to jack up the car and check the O2 sensor. dam i dont want to take off the spacer and intake. cuz thats what i am going to have to do, if i bring it in.
i never got the check engine light after installing the spacer, last year.

 

hey sorry for bringing an old thread back from the dead, but i am having the same issue (just posted a thread on it, before finding this one) did anyone figure out how to fix this? mine goes on and off the same way stays on for 2 days, then off for 4. all i have is a fujita intake

 

Apparently there is a TSB out on bad cam position sensors. It could be related.

Tony