SOS...Why does my car keep stalling?

My mechanic and the dealer have been unable to diagnose my broken 2005 Hyundai Elentra GT. For the past 7 weeks it jerks and shuts off while driving and often won’t start back up again. The check engine light repetitively comes up as a PO 420. I’ve changed an O2 sensor, my mid cat converter, and my manifold/upper cat converter. (I also changed my manifold at 72,000 miles 18 months previous when my check engine light went on with no symptoms.) Anybody have any ideas or know a Hyundai specialist (not the dealer!)??

Thanks! kara

Since we don’t know what city you live in or near how could anyone recommend a mechanic?

Well, you are probably on the right track because you probably need a different shop. Although P0420 says the catalytic converter or O2 sensors aren’t working, they probably are not the cause of your intermittent engine operation. In most cars, the car computer response to problems at the catalytic converter is to quit trying to use the O2 sensor data and switch to “open loop” mode. Open loop leaves the car running is pretty much the way all cars worked in pre-vehicle computer days which did not entail the engine stopping all the time.

Intermittent stalling is often caused by fuel pump, coil, spark plug wire or idle air control circuit problems. Some of those things don’t set DTC codes sometimes.

I believe that somewhere on this site, there are “Mechanics Files” that list shops that users of the site have found to be particularly easy to deal with and helpful. Why not try those?

Oh yeah, I live in western Massachusetts. However I could call a specialist anywhere.

Thanks for your detailed response. =]