Hello everyone,

My family's Volvo 240 engine idling rough and inconsistent, especially at the stop sign when the car needs to proceed, the engine hesitates. However, when the car accelerates it picks up RPM and power. I have done the following work on the engine and still am having problems with start up, rough idling, and running rich.
Replaced air idle valve
Replaced pressure regulator
Replaced throttle position switch
Cleaned the throttle body
Replaced fuel pump and fuel filter
Replaced Oxygen sensor
Installed new Bosch copper spark plugs
Ignition coil tested and is good
Air Mass Meter is good
Warm or cold, the idling is rough and oscillating. The initial start up is quite bad but as the engine gets warm it picks RPM. I very much appreciate for any ideas or tips you may have to share.

Thank you,
Habib

Test power stage (ignition amplifier). Check all ignition wiring. Clean and secure wiring grounds.

How are spark plug wires, distributor cap and rotor?

I can tell you from personal experience that air mass meters can test "good" but still end up being faulty. Or another way of looking at it is that it has not completely failed, but it is not performing as it should. You might try swapping in an air mass meter from another car that is running well. Junkyards around here (California) sell them for about $50, tested and with a 90 day warranty.

Have you checked engine compression? Are any of the cylinders significantly lower than their neighbors? You could have a burnt valve or some other valvetrain issue. But I would start with the AMM - they can cause all sorts of "head scratching" running issues.

Dear cdcrawford;

You sure were right concerning the AMM. Replaced the AMM with a re-manufactured one and the engine is running fine now. In addition, the air-box thermostat was found to be defective causing continuous hot exhaust air through the AMM possibility damaging it. The thermostat also is replaced. Thank you for your time and suggestion. Have a great day!

Habib