I would check the intake manifold for a crack or an intake manifold gasket leak. There is a smoke test that can be used to find the leak. Very cheap to do.
Because it happens hot or cold look to this first as a starting point. The extra air that leaks in confuses the computer on the mix of air and gas needed. This causes the engine to surge up and down.
Wednesday, June 6th, 2007 AT 10:37 PM