I have a 2004 3.4 and it is idling very rough. Also when the motor warms up and I go to restart it turns over but takes a while to fire. I do have an exhaust leak but so far have changed plugs, wires, EGR , and all coil packs. Not sure what to do next. It runs ok at speed but when you let off the gas it sputters and tries to stall

 

How many miles on the car? Is the check engine light on? Have you had the car scanned for any codes? A few possibilities that come to mind are an O2 sensor going bad or a bad (clogged) catalytic converter.

 

Clogged EGR passage
Dirty injectors
Defective fuel pressure regulator
Defective fuel pump

 

It has 195,000. It has thrown various codes, intermittent spark. 02 , and that it was running rich

 

EGR has been replaced, injectors checked out. Runs ok when you are up to speed

 

It also doesn't want to restart after engine is warm. It does start just takes a few

 

I'm actually experiencing a similar problem with my Cruze right now (rough idle, some weird but subtle power problems <30 mph), had it scanned and am suspecting a bad O2 sensor. It runs fine once you're up and moving, like you mentioned.

A bad O2 sensor will lead to an air to fuel ratio that is either too lean or too rich which will cause the engine to over consume fuel. O2 sensor replacement is recommended anywhere between every 60-100k miles on newer vehicles post 2000.

 

Problem solved finally. It was a fuel pressure regulator.

 

It was the fuel pressure regulator. Thanks