Hi, I'm new here. '93 SL sedan, SOHC w/throttle body injection, automatic. The car has 140k miles on it. As a reward, I gave it a new air and fuel filter, new plugs and O2. It has developed an occassional off idle stumble. Not really a stumble,more likeno response when the throttle is depressed. It acts just like the throttle isn't connected to anything. Happens rarely, so it has been hard to catch on a scantool. Scanner doesn't seem to show any dead spot in the TPS, but may be too fleeting to see? It also has an annoying sort of float, then jerk, to the performance when warn driving at steady slow speeds, like 25-30 mph. It feels like it has a mile of play in the drivetrain. Again, it only happens when warm and not all the time. Fuel pressure is rock steady @ 28 psi. Idle is also smooth. Along with this, the mileage has dropped approx. 5 mpg in my daily 70 mile commute. It has averaged a steady 33-37 mpg for over a year, on the low end during winter temps and high end during the summer. Last tank was 30 mpg. Any common problem to look for?[img]smileys/smiley6.gif[/img]

 

try a tune up

 

The stumble is an EGR problem. Simply unpluging the vacuum that operates the diaphragm cured the erratic operation and stumble. It still needs to be fixed but now I know where the problem is. The poor mileage was a result of the belt tensioner going bad and dragging the engine down a little. All readings on a scantool are returning to normal except BLM is a little high from lack of EGR flow, and light throttle at highway cruise will show a little knock retard from the same thing.