P2188 System too rich at Idle Bank 1

[pbierre]

My 2004 XC70's engine has been fault-free for the 2 years since I bought it. It's the 5-cyl B5254 T2.

After filling tank today, upon restart it threw a P2188

"System too rich at Idle Bank 1".

I noticed right away that the idle was choppy, almost stalling, then racing, then settling down. Driving home, the choppiness continued at
stop lights. It's almost as if the throttle is getting whipsawed.

What does the "too rich" error suggest?

[BillAileo]

Possible causes include
– Leaking fuel pressure regulator
– Leaking fuel injector

[pbierre]

Excess fuel injection (flooding) points to a problem regulating fuel injection. The sensor that controls it is the Mass Air Flow (MAF) sensor.

As a first crack, I cleaned the MAF sensor using a spray MAF sensor cleaner. This has smoothed out the idle, although it seems a bit high in neutral (800-900 RPM).

Will continue to monitor. I neglected to say the engine has 120,000 miles on it.