RepairPal is your advocate for car care advice and guidance

Q: car is running rough at 40 to 45 miles per hour on 1994 Cadillac Seville

Rookie cbe0621eac06868b3efe0d8d1d3611e23c60d3114864ea2ec19a68cfbd3eebab
The car misses at 40-45 in overdrive change to drive 3 and it quits any insight
No car image 94a1663db56199c5353592009e34aaa51078a2469bed068bb8d6f0ba43accf97
Get a Repair Estimate
Guaranteed by certified locations nationwide. Learn more
RepairPal estimates are guaranteed at over 1,700 quality certified locations nationwide. Learn more
A secondary ignition misfire can cause the conditions you are having. The ignition system components are under very heavy load when traveling 40-45 mph in overdrive. Shifting down to 3rd lessens the load on the ignition system and the misfire goes away. Chances are pretty good the a spark plug or spark plug wire is at fault. Only a complete inspection of the ignition coils, spark plugs, and spark plug wires will confirm this. If "carbon tracking" is found on any of the spark plugs the spark plug wire to that plug should be changed also. If your spark plug wires are original in may not be a bad idea to replace all 8 plug wires if fault is found with any of the wires.
Didn't find what you were looking for?