I have a 96 Regal Custom 3.1 with 238,000 miles which is having an idle issue. The RPMs will cycle fast/slow/fast/slow...etc ranging from 1500 down to below 500. The car has no noticeable loss of power while driving, but runs rough and almost dies at stoplights or low speeds. I found an exhaust leak recently (after it started) and ended up replacing the catalytic converter, rear manifold, and the donut gasket. The car does not act up when it is really cold out (it was 15 degrees when I brought it home after the exhaust job-- I thought that fixed it, once the outside temp warmed up it started again).


The mechanic who did the exhaust says it is the O2 sensor, another says EGR valve. No one seems to want to scan it without charging extravagant shop rates, any suggestions?