I just finished replacing my vacuum hoses and adding an efini y-pipe, downpipe and PFC. I also replaced my plugs and o2 sensor. now it is idiling rough and missing when idling. I looked around and couldnt find any exhaust or vacuum leaks. Does anybody have any ideas what could cause this? Could I use my PFC to check what is wrong??

 

Sounds like one of your hoses is in the wrong place...Retrace your vacuum lines.

 

Try adjusting your Air Adjuster Screw under the plastic intake elbow center on the throttle body. It may be that since you are running a downpipe, you need to readjust your idel air mixture. Remember how many turns you go so that you can put it back if it does not help.

If that does not work, try pressing the throttle linkage further closed with your thumb, or try gently prying the throttle linkage idel stop up a little with a flat head screw driver to see if you can get a positive improvement by manually adjusting the throttle valve. If it improves, then adjust the idel stop screw. Also make a mark so that you can realign the screw if you go wrong.

 

You are complaining of a rough idle and not a high idle correct? I agree with Foz, it's a vacuum line, not throttle problem. Also check your spark plugs and wires. Good luck.

Richard

 

actually, when i start it, it idles around 2000, then it slowly goes down to 800 when it is warming up. It is missing alot when idleing also. Then, when I rev it for a second and let it idle again, it idles up and down between 1000-2000 for a few seconds and then returns to the normal (abnormal) idle.

I was very careful with my vacuum hoses and I checked all of them at least 3 times. I also tested all the solenoids and check valves. I would feel really stupid if it ends up being a vacuum hose.

 

I did the same thing, I checked, rechecked and checked again when I did my vaccum hoses, however, I had one of the check valves backwards in the end. If you are 110% sure that you have properly done the hoses, then next thing to check is your TPS. Make sure it is reading properly from idle up to full throttle, this causes a lot of revving if not properly adjusted. As for the misfire, it's gotta be electrical, check each of your wires for spark.

 

well, i check my tps (this was very easy to do with my PFC), and that was working fine. spooledUP7 guessed right, it turns out that all I needed to do was to adjust the idle screw on the throttle body

but while trouble shooting it, I did find some loose hoses and a (small) exhaust leak due to a bad downpipe stud. My car runs great now, it has a perfect 10-8-10 boost pattern and it idles around 700-800. Now I just gotta fix those soggy bushings.

thanks everybody for your help!