Okay I have a 2000 GMC jimmy with the 4.3L, around 109k. About 3 weeks ago, my engine started to shake, almost like it was choking, whenever i would crank it in the morning. The check engine light came on, so i went to autozone and they said MAF error and a bank was lean as well. So I replaced the MAF but still nothing. Cleaned the EGR no luck either. Im thinking it must be an O2 sensor? Anytime it sits for over a couple of hours it spits and sputters for about 3-5 minutes into driving before it levels out smooth. Im lost......

 

What were the specific codes? Have you checked for any exhaust leaks ahead of the O2 sensors?

 

It dawned on me to get the numbers about a mile or two down the road. By then the SES light had turned off. What would be the best way to go about checking for leaks? Visually or is there a method that I'm unaware of?

 

The PCM stores trouble codes. Have them read anyway.

As far as locating leaks, I use an old stethoscope with the end off. Listen for air pulsing out.