My daughters 1987 volvo 240 is running too rich and did not pass emmissions inspection today. The car had sat for a while prior to her purchasing it. She also has complained of poor gas milage. I would appreciate any input of wjhere I should start looking for the source. the car starts fine and seems to run good, no problem idling, but has arough spot when decelerating.

 

May be your Mass Air Flow Meter or your O2 senor. Have you check for codes

 

I am unsure where to check for codes. The oxygen sensor appera to have been changed recently. How can I diagnose the MAF sensor?

 

It is a good idea to buy a Haynes Manual....The code tester should be on the left side (sitting in car) under the hood just behind the wheel well...little black box...the top comes off and there is a test led on the side of it..put the test led in the #2 hole press the botton...a light should come on...release the button and then a sieres of blinks will happen... 1-1-1 means no codes..the our codes are in the book and I dont have mine handy...good luck

 

The 1987 model doesnt have that so you cant check for codes. U have to check manually getting voltage reader and check the voltage coming from the mass flow sensor and the O2 sensor *** well.. Don't know the voltage the sensors get but i will try and and find the specific voltage u have to get.. But you can allways start by doing a tune up, like: spark plugs and wires, cap and rotor, air and fuel filter change, cleaning the throttle, throw a bottle of injector cleaner.