I drive a high (265k) milage 02 QC 24valve HO 6 speed. While on a 340 mile trip and on cruise control at 62-63 mph after about 2 hours running, engine missed a couple of times and speed began surging slightly. I did not notice if tach and speedo were moving to gether. Disabled cruise and truck began running smoothly. Did not notice any voltage variation, 6 mo old batteries. After about 10 or 15 minutes enabled cruise again and same thing after a few minutes. Turned off cruise and resumed trip. Next morning tried cruise control on 15 mile trip to dodge dealer with no problem.
Dealer could not replicate problem on road tests with engine up to temps. Dealer indicated no codes in memory. Possible PCM problem per dealer, but not sure. Dealer indicates this model truck has cruise control components contained in PCM. Since the problem is unique to cruise control, is there any thing else that could be causing the problem external to the PCM?
Any help would be appreciated
TNX Edward L Frazier

 

If rear axle speed sensor(abs) acts up, it will affect speed control and engine performance. So could the brake switch(usually kicks off completelly), APPS switch, speed control swithes,wiring in steering column. Sort of doubt is PCM, but carefull wire check and grounds cleaning is good thought.