K87ZZ4

O2 reads in the 800-900+ mV range pretty consistently. It occasionally sets a Code 45.

I’ve replaced the IAC and the O2 sensor, checked for vacuum leaks, tried disconnecting (and plugging) the lines from the EVAP, disconnected (and plugged) the tubes in the A.I.R. system. Nothing has made any difference.

Any ideas about the most likely culprit?

It started running rich at idle a few years ago (discovered in emissions test) and has just gotten progressively worse.

jv9999

My first thought would be one or more leaking fuel injectors.

Cliff Harris

A ruptured fuel pressure regulator diaphragm will cause your symptoms. Check for fuel in the vacuum line that attaches to it.

K87ZZ4

Thanks for the ideas. I checked the fuel pressure and it's running about 40 PSI. I pulled the vacuum hose off the regulator and it's dry.

Is there a way to see if an injector is leaking without removing the injector?

jv9999

Shut the engine off while watching the pressure. With good injectors and regulator, it should hold the pressure for a least a couple mins.

Another thing that will cause a rich condition is a misfiring cylinder. How old are the plugs and wires?

Cliff Harris

Are the spark plug wires OK? Check in a dark garage...

K87ZZ4

It holds pressure for a few minutes and was at 20 PSI after 15 minutes.

I *thought* I had replaced the wires when I replaced the plugs, cap and rotor (3 yrs ago), but I may not have. In that case, the wires may be over 10 yrs old.

A while back, I pulled a couple of plugs (#5 and #7) and found both to be pretty fouled with black soot. I'm thinking maybe all of them are fouled, rather than just a single cylinder misfiring.

Cliff Harris

It is common to cross the plug wires for #5 and #7. That will cause the plugs to fire at the wrong time and those cylinders will be dead. I suggest pulling all the plugs to see what's really happening.