M45 runs lean after longer drives

[ple99]

My 45 will run lean after longer drives. Usually one hour or more. No trouble with shorter drives.

It gets the irregular idle and throws code for being lean on bank 1. P0171.

I know this means air is getting in somewhere. Since it only happens on the longer drives does this indicate maybe a head gasket? Or any other particular place?

Thanks.

[Ilya]

I'm not familiar with this code but this page gives a list of possible culprits:

http://www.engine-codes.com/p0171.html

I would check all your hoses and tubing, etc. Start with the basics. Maybe replace the PCV valve ($5 and 10 min of work) and clean the MAF (be very very careful, they are sensitive!) with MAF cleaned. Maybe replace the air filters if they are old.