99 vic running rough

I just changed my intake manifold, (it cracked at the thermostat housing and spewed all over the engine) and when I started the car up the first 2 times it stalled. Ever since it has idled rough and when I am driving it feels like a cylinder is mis-firing. I do not get any code, no light(check engine). There is a lack of power and it is noticeable. I double checked all wires and hoses. I took off all the COP's cleaned them and put them back. I am going to change the plugs again(they are about 6 months old). I am at a loss to figure this out, the car was running great before the manifold cracked. has anyone else had this problem or have any possible solutions? Thanks in advance for any help.

You made sure that the plug wells were dry before inserting the COPs, right? And you used dielectric grease around the ends of the COP boots?

Other than that, it may be a vacuum leak around the manifold or one of the vacuum hoses. Or you may have forgot to plug a sensor back in. Are all connectors attached firmly?

I got out today and put in new plugs, checked all connections and hoses, put di-electric grease in every boot and it still seems to be hesitating! I am thinking of changing the egr valve next although it seems fine, other than that it's swap out all of the COP's and injectors to see if that is the cause. I'm stumped!:runaround:

Test the EGR first. I take the vacuum line off of the fuel pressure regulator and attach it to the port on the top of the EGR valve. If the engine RPMs initially drop off from the EGR, it's working properly. If you hear no change like the EGR is constantly open, than you need to check the DPFE sensor. These are known to get condensation in them and send incorrect data. Usually taking them out and smacking them in your hand to get the water out fixes the issue, but is not always the case.

The DPFE sensor is located on the rear of the passenger side head. It's held on by two bolts and has two hoses running to it which can just be pulled off.