Expert: Brad Sears - 12/3/2007

Question
'79 Cutlass, 260 Engine. Weather is turning colder so I warm up my cutlass for 3-4 minutes. When I tap the gas a few times after she's warm in Park,it revs nice and smooth so I assume she's ready to go. When I pull out of a level driveway, she tries to die out unless I can tap the gas to keep her alive. Problem goes away after 1/2 mile or so. What has changed just because she's in Drive ? Any tips?

Answer
What you are experiencing is the reason that we have gone completely to fuel injection. Given the governments restrictions on emissions and fuel economy it just was not possible to make engines run under all condition with a carburetor. In the trades many good mechanics in that era went totally bald from tearing their hair out trying to solve these warm up condition stalls and shudders. What this sounds like it could be is the timing of the opening of the EGR valve in relation to engine warm up, the timing of the heat into the carburetor from the heat tube and thermostat in the air cleaner, and perhaps the thermostat in the engine could be opening a little too soon. Add to this the mix of alcohol in today's fuel, dirt in the bore of the carburetor changing the effective opening of the throttle plates and thus changing the timing of ported vacuum and of course now load on the engine when you shift into drive. My 79 Pontiac has always from the day it was new until I changed the engine a year ago always did this same thing, and I tried every trick in the book to fix it. I could change it, but it was always there. Now with an after market Street Rod throttle body computer set up it is fine.
Brad