Luke13

My 03 GT has been throwing up a code for running lean. It has only started happening since the weather has gotten colder, and also on days where i haven't driven the car for a day or so. I cleared the code with my tuner and it stayed off for about a week. Another cold front came thru, and the car sat for a day, then put the code back up.

I've also had a problem with idle, it doesn't happen always but seems to be random. The car will idle down after being cranked, then fluctuates between 500 rpm and regular idle. It will do this while sitting, then go away after driving.

What are possible causes of these problems? Are they related? I've seen many threads on this, but they seem to go off topic and haven't found a good place to start.

cliffyk

What is the code(s)?

A sluggish/dying front O2 sensor can cause the problems you describe.

Here is how to bench test a narrowband O2 sensor--though they are cheap enough and if they've never been changed almost any New-Edge GT is due to have them changed...

Luke13

The code that keeps popping up is p1131.

I've done all the basic things to check for running lean.. No obvious vacuum leaks, my rear o2 censors are off, I'm running 93 octane with a 93 octane tune. So it looks like it's time to start replacing parts. I'm looking for the best place to start?

Stevo86

I would look into possible vacuum leaks as well.

Luke13

So I've found some oil residue coming from under the PCV hose where it connects into the front of the throttle plenum. I have the BBK throttle intake and had to replace that hose elbow since the last one collapsed and formed a hole in it. Obviously oil is making its way out of the hose, but i don't notice any odd noises or problems like when the original hose had a hole in it. Could this possibly be my problem though?

Stevo86

Doubtful, a little oil through the PCV is normal.