Volvo 240, 1988, Iding Problem

JOO · Post by **JOO** » 13 Mar 2009, 23:59

We have Volvo 240 that we are trying to fix after it has been idle for 4 years. The problem we are having is that we are unable to set the idling. It is very high, we suspect the Bosch FD could be the problem given that the car has not moved for sometime, but we are not sure. When driving, it is not smooth, it keeps jerking, any idea on how we can fix it?

Post by **billofdurham** » 14 Mar 2009, 13:08

Welcome to Matthew's Volvo Site.

When a car has been standing that long there are many parts that can deteriorate or stop working due to lack of use.

When you decided to take this on did you drain out any old petrol and refill the tank with new? This is very important as it can cause many of the problems you seem to be experiencing.

For erratic idle you need to check:

Mixture and idle speed adjustment.
Accelerator linkage is functioning correctly.
All air and fuel hose connections.
Idle air regulation valve.
Fuel pressure.
Fuel injectors.
Coolant temperature sensor - this is the sensor that supplies the Electronic Control Unit with information and not the sensor for the temperature gauge.
Air Mass meter.
Air induction system under pressure.
The throttle valve housing is clean.
ECU connector.
Initial opening of throttle valve.
Throttle position sensor adjustment.
Valve clearance are correct.
Engine compression is normal.

Bill.

JOO · Post by **JOO** » 18 Mar 2009, 10:03

Yes we did drain all the fuel and in fact cleaned the tank, replaced tank fuel pump and the other fuel pump under the body. We re-checked the items listed except for ECU connector. There seem to be high fuel going through the system during idling, and less fuel when the car is moving.

Post by **billofdurham** » 18 Mar 2009, 13:42

That rules out 'dead' fuel.

We re-checked the items listed except for ECU connector.

When you checked the engine temperature sensor did you check for resistance and voltage which, apart from replacing it, is the only way to test it?

Below is a description of, location and method for checking the sensor. This is one of the most common causes of poor starting and running. I posted this for member waynej last week.

Temperature sensor defect. The engine has two temp sensors one for the gauge which is mounted in the head under intake header #2. The other is for the fuel injection and is mounted in the head under intake header #3. This sensor is a negative temperature coefficient thermistor. As the temp drops, the resistance rises, and as the temperature rises, the resistance drops. Therefore, if you have a broken wire, defective sensor, or even just a bad connection the resistance measured by the sensor and passed to the ECU will be very high or even infinite. The ECU interprets this as minus many degrees and pours in the petrol to compensate. This would lead to the type of starting you are experiencing.

Sensor resistance "cold" should be around 6,000 ohms at 32 degrees F (0 deg C), 2300 at 68 degrees F (20 C), and 200 at 212 F (100 C). You can also check the wiring between pins 13 and 5 at the LH ECU, with the sensor disconnected, resistance should be infinite. Voltage with the ignition ON and sensor connected, measured between pins 13 and 5, should be:
0 C=around 3 volts +/-.5v
20C=around 2 volts +/- .5v
100C=around .3 volt +/- .1v
If these aren't correct, check the connections in the sensor wiring harness. Check engine earth connections at the intake manifold. If the voltage is zero, your ECU is at fault.

Bill.

dannym · Post by **dannym** » 19 Mar 2009, 05:34

Could have a vacuum leak.

Maybe replace all vacuum hoses.

Danny