Rough at idle

[Douglas Cook]

My 3.8 is sometime running rough at idle immediately after first starting. It seems to clear up quickly after I raise the rpm or start my trip This only occurs after I have had the engine shut off for 10 to 30 minutes. No check engine lights are being shown. Could it be my maf sensor?

[kmohr3]

I'll betcha 5 bucks you have a bad fuel pressure regulator. This happened to my father-in-law's 3.8 Liter LeSabre.

What we noticed was: (1) slightly more excessive cranking time, (2) stumbling and running rough for several seconds after starting. Basically, what happens is the fuel pressure regulator lets fuel leak out of the fuel rail and it takes several seconds to build up fuel pressure before the injectors start spraying well again

One way to check it is to pull the vacuum line off the pressure regulator and see if any liquid fuel comes out - if yes, you definitely need the regulator. It's easy to change, and we bought one for the Buick at Advance Auto for about $30. Just be careful when opening up the fuel system - I had my fire extinguisher nearby (especially with a hot engine - just a precaution).