tripper80

I noticed that on OBDII reader, the control module voltage can drop as low as 11.3V on highway which is much lower than the alternator output of 14.5V. Will it an indicator of a bad grounding?

*Online search tells me the Control Module Voltage is the battery voltage minus any voltage drops between battery and ECU

Moto_Guzzi

Which problems do you notice about functioning of the car-?

tripper80

reason for observing the voltage is that my engine has intermittent shake both idle and on road, more noticeable on idle. I thought the very low voltage may lead to very weak ignition or even misfire.

update:

1.today I replace all spark plugs, checked all coil and all are with similar specs. So ignition system should be fine.
2.opened camshaft cover, replaced both tensioners. checked timing belt and gear teeth, they look both in good shape.so timing should be ok.
3.checked all vacuum lines and replace one aged seal with good one.
4.checked grounding, battery -pole to engine block, to car body, engine block to car body. all look in normal situation.

noticed that the temperature sensor before the throttle valve may dead, because I see no RPM change when unplugging it. thinking of replacing it.