1991 240 Emissions Fail High CO13%

paulcblais · Post by **paulcblais** » 23 Dec 2013, 19:14

I'm running out of options. 1991 Volvo 240 with 62,000 miles on it. Fails emissions due to running rich.
Idle CO13% HC600PPM 700 RPM
Cruise CO13% HC600 PPM 2500 RPM
Have changed plugs, wires, cap, rotor, O2 Sensor, Coolant temp sensor, Thermostat, opened air box thermostat.
Injectors are not leaking, no vacuum leaks, cleaned flame trap, Fuel pressure regulator not leaking.
Shows codes 113 and 232. Starts fine, Slight miss at idle. On the road runs beautiful. No hesitation. Unplugged MAF and it goes into limp mode.
Have the LH 3.1 fuel management system. MAF measures 2.6V at key on and 3.6V at idle.
Not sure where to go from here. I don't want to throw money at this thing without understanding why.
Suggestions / Ideas Please
Paul

paulcblais · Post by **paulcblais** » 23 Dec 2013, 19:21

forgot to add... It seems like the computer is keeping it in open loop and not recognizing it's warmed up. Could i have a bad computer? UGH

lummert · Post by **lummert** » 23 Dec 2013, 22:00

Maybe coolant temp sensor is defective, or the wiring to it is bad.

paulcblais · Post by **paulcblais** » 23 Dec 2013, 22:27

possible but everything looks clean and operational, I'll double check it though.

paulcblais · Post by **paulcblais** » 25 Dec 2013, 08:24

At what temp/resistance does the computer switch into closed loop mode?