Cadillac Repair: Surging, egr system, throttle positioning sensor

Question
  Have a 1991 Cad Deville, with 45,000 and when coming to a stop (below 15 mph)car will surge (sometimes violently) before stopping. It does this about 50% of the time...other times the stop is normal and smooth.  Several mechanics have been unable to solve problem...thanks for your help...Dave

Answer
There are so many possible causes that can cause this type of problem that it would take hours to list them all. Since so many people have had their fingers on the engine and can just imagine how many things have been ADJUSTED and or MISS-ADJUSTED trying to resolve your problem.

Without actually having access to the vehicle, there is honestly no way for me to tell you what is causing your problem.

The most overlooked items are:

1. A residue buildup within the throttle plate and idle air by-pass circuits.

2. A faulty EGR system.

3. An intermittent fault in the TPS (Throttle Positioning Sensor) of which normally does NOT cause the CHECK ENGINE light on the dash to illuminate.



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