High idle and running rich (P0507, P0172, P0175)

[Jason Cheng]

I have a 2002 silverado with 5.3L engine. It has suddenly started idling high at startup and the check engine light has come on. The codes are P0507 (high idle), P0172 (bank 1 rich), P0175 (bank 2 rich).

 

Anyone have any idea what is wrong?

 

If it was just the idle air controller or throttle, that would explain the high idle but not the rich running.

If it was a vacuum leak, that would explain the high idle but it should be running lean in that case, right?

I guess a faulty fuel pressure regulator could explain all the codes and symptoms.

[carkhz316]

Pull the vacuum line off the regulator. Even if it is dry, start it up and watch for it to start squirting fuel. I've watched on take upwards of a minute or so of running before it started leaking.

[Jason Cheng]

I pulled the vac line off the regulator and it was dry. I forgot to wait for up to a minute for a leak to develop though.

[Jason Cheng]

I fixed and it was indeed the fuel pressure regulator like I initially thought. It was apparently not the normal mode of failure for fuel pressure regulators in general. It never leaked any fuel through the vacuum line and I believe that this was because the diaphragm was not broken which is typically what happens to fuel pressure regulators. The body of the regulator was extremely rusty and it looked like it was cracking apart. Shame on Chevy for not painting the regulator to begin with.