Your fuel pressure should be 60-66 psi with csi and 56-62with sfi. That may be part of your problem. Alsoc clean the throttleplateon both sides and the iac hole. Also your injector lines could be cracked if under the nmanifold. That could cause the up and down revving.
If the fuel pressure is less than 55 psi (379 kPa) at idle, it falls into the following 3 areas:
? The pressure is regulated but less than 55 psi (379 kPa). The amount of fuel reaching the injector is sufficient, but the pressure is too low. The system will run lean, hard starting cold, no start, overall poor
performance, and may set a DTC. See NO START DIAGNOSIS .
? A restricted flow causing pressure drop. Normally, a vehicle with a fuel pressure of less than 44 psi (300 kPa) at idle is inoperable. However, if the pressure drop occurs only while driving, the engine will
normally surge then stop running as the pressure begins to drop rapidly. This is most likely caused by a restricted fuel line or plugged fuel filter.
Friday, January 6th, 2012 AT 9:24 PM