SES light. From reading around seems this is probably a dirty MAF/broken MAF, vacuum leak or O2 sensor. Does theintermittent nature point to any one thing in particular? It doesn't go off much (5% of the times I start her up) but mostly in colder weather.
Thanks...Nick

 

What's most important is when it sets on. You dont have a 174 so it probably isnt the MAF or a vac leak.

Read your spark plugs

It could be the O2, you could try swapping it with the one behind the cat

 

What are you driving?...

If it's a '96+, I like to test O2 sensors by swapping them side to side. Then if the code changes from P0171 to P0174.

 

Swartlkk, rather than start a new thread on this code, I will renew this one to share my experience. Also, I want to thank you for helping so much.

I had a P0171 several months ago and swapped the O2 sensors as you suggested. First I sprayed them with carb cleaner as someone on this forum had suggested. I did not get the P0171 back, but I didn't get the P0174 either. So now I don't know if the problem was a fouled sensor or maybe the connector was faulty or something else. Anyway the SES is off now. My '96 was sitting a long time and rusty underneath before I started working on it earlier this year.