Tried out the elm327 device today to use with rev on the iPhone.

It all works ok but now the car seems to have a rough idle and a slight knock.

Could this be coincidence that something else happened at the same time or could it be the device?

Are these things able to write to the the computer?

Thanks

Won't be the elm. These cannot write anything other than clear faults.

I have one and used it loads with dash commander.