My '99 SLS has been dying on me at idle after the engine is completely warmed up. Earlier, I got two codes to replace one O2 sensor and a Crank sensor. I bought both but a shop in town said that I only had one. Then I had a torque converter clutch code which was repaired(overhauled transmission). The problem persisted so I replaced the fuel filter and treated the fuel for water and used some injector cleaner in the fuel. No change. I checked the fuel pressure with the pressures low but within limits in a Haynes manual. As the engine warmed up, the needle on the gauge would vibrate about 3 psi total and got worse the warmer it got. So, I replaced the fuel pressure regulator. Tonight, I got the same thing. After about 20 miles of driving at a good cruise (and passing some slowpokes) with no problems at all, I pulled up to a light and it died again. Is there a Low oil pressure switch independent of the one for the dash light? My oil pressure light does not come on unless the engine is off. Where else can I turn? My troublshooting skills are getting a good test!

 

What about cleaning the IAC and throttle plate?

The oil pressure switch would only let it run for about 30 seconds before cutting fuel.

 

Also check the EGR to make sure its not carboned up