As I am driving down the road my pickup stumbles for a few seconds and check engine light will come on intermittently while stumbling. The check engine light does not come on every time and only flashes for about a second when it does.

The stumble goes away after a few seconds and doesn't happen as often when driving at highway speeds.

I recently changed the O2 sensor and have an exhaust pipe thats needs welded, not sure if this would cause stumbling.

Any ideas on a fix?

 

Even though the CEL was only on briefly, many codes are stored. Start there.

http://web.archive.org/web/201410310...26diagnosi.pdf

(The special service tool really exists, but everybody else uses a paper clip.)