88volvo760 turbo/auto transmission Topic is solved

Glenda25 · Post by **Glenda25** » 11 May 2005, 15:52

Appreciate any advice. Please email: [email protected]

1.Tachometer bounces back and forth and sometimes goes to zero and the car dies.
2.In park, revved up to 4000 rpm then it bounced down to 2000rpm and then back up several times. When slowly released gas pedal, rpm fell to normal idle.
3.This usually does not happen in the first trip of the day but after driving and stopping for a while.
4.Parts recently replaced: in tank fuel pump (external fuel pump OK), fuel pressure regulator, spark pugs, the green #B fuel relay (under dash), black system relay (under the hood), injector ballast resistor (driver side fender wall), ignition control relay (next to ballast resistors)

Glenda Fair Oaks/Sacramento, California

LaRy · Post by **LaRy** » 12 May 2005, 12:42

I would maybe divide this into two separete problems. I twice had the tachometer problem, bounces back and forth sometimes and goes to zero and the car dies. The tachometer is connected straigh to ignition coil, so the fact that it is bouncing up and down and goes to zero is telling us that it is something wrong with the ignition. I had to change the Hall-sensor and some years before that I had to change the ignition amplifier.

It could also be the same problem, because the sensor is also giving information to the electronics about motor speed and if you get bad speed information to the electronics, the function with idling speed would most probably be bad, like you describe. It is also typical for a sensor that when it is going to die, it is working bad first when it is heatened up by the engine. Probably is this sensor assembled close to the flywheel.

Glenda · Post by **Glenda** » 13 May 2005, 08:35

It seems that the hall sensor may be my problem. What does it do? Where is it located? Does it have another name? I can't find it mentioned in my manual. Thanks

LaRy · Post by **LaRy** » 13 May 2005, 12:38

I am not any expert in the V6 engine that I suppose you have, but according to the information I can find, the sensor is placed in the distributer, just under the rotor. In the old days you had contact fingers to adjust in the distributer. Now you have a sensor instead, making it maintainance free. The problem could be as simple as corrosion in the connector between the distributer and the cable going up to the ignition amplifier. From that amplifier it is going a wire with pulses to the ignition coil making sparks AND to the electronic unit. Sorry if I do not know the correct English name for all those componets, I'm Swedish.