tomf

Yesterday I pulled a spark plug to check its condition. It looked OK so I replaced it. Today, I started getting a P0171. Could a defective spark plug cause a P0171? Is this just a coincidence that after pulling the spark plug that I started getting a MIL light?

Here's my freeze frame data:

shrtft1 -8.6
longft1 16.4
shrtft2 -7.0
longft2 19.5

BTW I've had a p0171 recently, about a year ago, and replaced the MAF and bank 1, sensors 1 and 2. Haven't had any trouble until today.

tomf

Looks like it was just a coincidence. I replaced the front (bank 2) 3 spark plugs. Still was getting P0171 system too lean. Last week, I cleaned the IAC and throttle bottle so I decided to recheck the hoses and clamps. But before I did that I took out the MAF and cleaned it even though it looked clean. Then as I was tightening down the clamps on the air intake I noticed that a hose running into the air intake canister was disconnected. I reconnected it and on the following test drive the MIL went away. I think its interesting that it took 7 days for the for the MIL light to come on if the cause was me leaving the hose off the intake canister. Anyway I'm glad the MIL light is out.

To summarize the actions that corrected the problem (Don't know for sure which one corrected the problem):
1. Cleaned MAF
2. Tightened down the air intake clamps
3. Reconnected hose on intake canister.