My 90 Eldorado (98K) runs and drives great except from start or very low speed. When I press the accelerator, the car "stumbles" slightly or hesitates, there is a slight shaking feeling as if the car is running over rough pavement, and then the car runs great. It accelerates great at highway speeds and rides perfectly smooth. Could the car need a tune up? What do I need to look for?
I did check the codes - in history I found E017 "Left oxygen sensor not ready" I bought this car a month ago and checked the car's history/paperwork - a tune up seems to be the one thing NOT done to the car - it has been extremely well maintained otherwise - what would a "tune up" entail? Thanks!

The left (rear) oxygen sensor is either not warming up or the circuit is open. It may be clogged up... You can check for continuity between the sensor and ecm, but if you havent already replaced the sensor, I'd do that first.

A tune-up usually means replace:
-spark plugs
-wires
-distributor cap
-rotor
-O2 sensors
-air filter
-fuel filter

Any history code should be written down then erased. Recheck next week and if no further codes, the sensor is ok. Car is 8000 milesoverdue for spark plugs, stay with DELCO. I also recommends wires as well.

I found a service record from May 2006 -- Car had 89K miles (currently has 98K): Scope ignition, RR distributor rotor, 2 spark plugs replaced (#1 and #6 -- Champion platinum), injector cleaner

Thanks!

I found a service record from May 2006 -- Car had 89K miles (currently has 98K): Scope ignition, RR distributor rotor, 2 spark plugs replaced (#1 and #6 -- Champion platinum), injector cleaner

Thanks!

in other words they probably just took a file to the contacts on the rotter and the distributor and replaced 2 spark plugs that liked dirty and put a bottle fo some injector cleaner in the tank . best bet is to do a complete tune up and then see where you are at as far as the rough idle goes . probably wouldn't hurt to clean the throttle blades and rod out your egr tubes

A good check for ignition system maintenance is to have a look at the spark plug wires. The original wires came from the factory numbered according to their position. Replacements (even AC Delco) will not have this feature.

IF the wires are not numbered, those are most likely original as well. At that point you might as well do the cap rotor and plugs for peace of mind and a starting point for your own service intervals.