I'v been working on a trouble code po171, comes and goes, have changed both of the O2 sensors, looked all over for a vacuum leaks didn't find any, I noticed that the vacuum line going to the fuel pressure regulator doesn't have any vacuum on it??? Is this normal?? I checked the line and its clear, pulled the housing off the throddle vlv and have alot of vacuum there but not pulling anything on the regulator....is there a problem??? its a 2003 chevy cavalier 2.2 eng

First thing to check is your fuel pressure. It should be 50-60 psi with the key on and engine off. Do you have any other trouble codes along with it? Does it have an actual driveability issue? Meaning can you tell that it is not running right? Does it cut out, die or? When the code was read did they/you check the freeze frame data? A quick way to check if there is a hole in the diaphragm of the fuel pressure regulator is to smell the vaccuum hose going into it. It should not smell like fuel. There are many things that could cause your problem so it is a gradual process of elimination. Do not start taking stuff apart and changing out parts. This is a common mistake and will compound your problem and cost lots of money. There could be contaminates in your fuel, a plugged filter, a bad injector etc etc etc.

what r the conitions outside when light comes on? ei. cold wet hot ive had to replace intake gasket on one before

It doesn't seem to matter what the weather is, I took and sprayed carb. cleaner all around the intake and didn't find any change in the eng.......not saying thats not it, just that it didn't change the way the eng. was running.....

"BadGirl", fuel psi is 55, no other trouble codes, it drives fine till the code comes up then die's but starts back up, guess I am not sure about the freeze frame data, no fuel smell in the vacuum hose, I'll take a closer look at the fuel in the tank and filter......what bothers me is there's no vacuum on the hose going to the fuel pressure regulator, that has me puzzled......

id take the trottle off and clean that port of throttle body no vacuum equal higher fuel pressure try sticking a paperclip in there with throttle body cleaner to clean it out and clean throttle plate and bore