Hi all - strange situation:
1997 Accord LX 4 cyl. F22B2 engine.
Recently the tachometer started jumping all over like crazy when gas is given - car would sputter and bog down during this time, but not every time.
Replaced the ICM, and still the issue remained. Replaced coil - and issue remained.
When the OBD 2 scan tool is hooked up (hung it on to read rpm and timing data) the problem vanishes. When unhooked, voila, it re-appears. It is like throwing a switch - I can do it in the space of seconds over and over, and it is perfectly consistent. It never fails.
I'm imagining the scan tool is providing an alternate ground path possibly? Anyone ever have any experience with something akin to this?
Thanks

 

May be a ground wire issue, the scan tool may be supplying the ground.

Check ground G101 connection.

 

See this other thread where the scan tool can supply ground:

https://www.hondaaccordforum.com/for...scanner-51949/

 

Beautiful - that was it! Went out, and that bolt was loose. Must have not been snugged down after I took the manifold off last. Thank you.