My '94 Astro ( throttle body, vin z but vortex valve covers).(?) Ran great at first, then on the highway 67-8 mph started a little bobble when climbing a rise. this would change with any change of throttle position. Got worse and worse, now stutters as soon as shifted into high gear, acts like the spark plugs are breaking down, but they're not that old. either are the wires, cap & rotor. Used to get 22-3 hiway mpg, now about 16. Trouble code at first read: IAC valve - replaced- no change. next read: throttle position sensor - replaced - no change. now reads: EGR - replaced - no change. Sometimes it backfires.
Mar 23, 2009 at 9:41 AM