Aldl connection corrupted data when engine running

[1project2many]

89 G20 will have slow updates. What is an example of the corruption you're seeing?

[steveo]

as a general rule on any car if the log data is clean when engine is off, but becomes corrupt with engine on,

- try running with alternator disconnected. if situation improves, replace alternator (failed alternator rectifier is introducing AC current into the system)
- try jumper cabling chassis to engine to ECM. if situation improves you have a shoddy ground cable
- try firing engine up in the dark and mist water all around the engine with a spray bottle. if you see sparks, you have a spark plug wire or coil or something with insulation breakdown producing RF that is screwing with your data stream