97 venture 177k mi runs rough at start

[cjstew4]

About once a week on morning cooler start up idles/runs rough like on 5 cyl for a few miles, then it's fine the rest of that trip, even other start ups and trips throughout the day. Throws the Service Engine Soon (SES) dash light but will not stay on long enough to have the mechanic read it. Sometimes the SES will stay on long enough to get it to the mechanic, but that's on a Sunday when they are closed. Had the 02 sensor replaced a few months back with the plugs and plug wires about 70k mi ago. Hard to time it to throw the code in front of the mechanic. Until then, any probable causes you can point to? Thanks in advance.

[97Venture_Chick]

7days a week, Kragen Auto Parts is open. Next time that light comes on, get into a Kragen store and ask to use the OBD2 scanner. It is free, but you have to use it in the parking lot. Im in California, therefore rough smog laws, but it could be the EGR valve. My venture had those issues a while ago, and it turned out it was the O2 sensors (front and back) and the EGR valve. Try and get into a Kragen next time that light comes on and run the test there.