Check engine light is on?

Well I work nights which means I am at work. I have the paper at home I will have to get that to you later. Thanks.

P0171 and P0302.

So maybe the coil pack. Hmm okay.

I do not know how to check for vacuum leaks. Okay, I will just sell it.

The check engine light comes on when the weather dips below -7 degrees celcius (or so). Usually when I hook it up to a diagnositc machine, I get one of the following codes: P0171 or P0174.

Today while driving to work, the light came on again. I hooked up the scan tool, and it came back with NO codes. The light was on, but no codes were present? How is that possible?

My O2 sensors seems to be working fine according to the scan tool (the graphs are not just flat, there is some movement), so what else could be causing the problme? Specifically, what could be causing those codes? Why does this only happen in the cold weather?

Help? Thanks.

My check engine light came on, so I took it and pulled the codes. It said it was running lean on bank one and bank two. The guy at the shop told me since it was running lean on both banks, it is a bad mass air flow sensor instead of bad O2 sensors. I replaced the mass air flow sensor and he disconnected my battery to clear the code. I live in the houston area and emissions are important for inspection. I got my car inspected, then about a month later the check engine light came on again. I pulled the codes and again it is running lean on bank one and bank two. What should I do?

I haven't heard any hisssing commonly associated with a vacuum leak. When I reset the code by disconnecting the battery it will take about a month before the light comes back on. I'll run it and see if I can find any though. Any other suggestions. I have noticed it sometimes wants to bog down slightly when I hit the gas pedal at a light or stop sign, but then the rpms pick right back up.

Every time I start my car, the rpm starts going down and then it would jump up and it does that for about 3 minutes and sometimes it will turn off, and then (almost every time) while I am driving, the car starts jerking and without moving my foot off the gas pedal, my speed would go down by itself and then will jump back up by itself after a couple of minutes, and the check engine light flashes during that time (The light is always on usually in my car). Any ideas? BTW I did try and use fuel injector cleaner, because I was told that it could be the problem but did not work. I appreciate any help.

Engine Performance problem
1999 Ford Explorer V8 Two Wheel Drive Automatic 150k miles

Replaced everything to do with the EDIS module ignition system. Still kicking a miss fire code, seafoamed it out. Notta, checked all the vacuum lines on it. Cleaned them out and also looked for leaks. Throttle body looks good and no issue. Fuel pressure is at 40psi, which is good. Runs good until cel comes on, so closed loop mode. Just has a check engine light that seems to never to want to leave.