I've noticed that even when I am coasting, the instant mpg guage on the HCHII goes to zero for a couple of seconds. This mostly happens when the engine is still cold. Is this a pretty common occurrence or does my car have a problem?

btw..the car is still new, with less than 7k miles. I havent even done an oil change.

 

I've noticed the same thing on mine during its warm-up period. My speculation is that it sort-of recalibrates itself once the engine hits certain temperatures--either warmin up or cooling down with coasting. When I see it, I just tap the gas pedal and it goes back to normal. I've had my HCH for a little over a month now, and about 1200 miles.

 

Search for "samba" and you will find several threads relating to this (since the iFCD "samba dances" it's way down to zero and the back up to 100...). It is thought to be a recalibration and it happens frequently on my car--mostly when the engine is cold.

 

Bingo on the recab. There was an old thread about it and someone brought up that it is explicitly mentioned in the owners manual -- an easy one to miss.

 

I'm sorry, can you give a link to that thread. I remember seeing it a long time ago but now I can't find it. The search thing on this forum hasn't been working recently and not even google brought it up.

 

I had a thread on this awhile back.

I found the answer in the Tarabell HCH bible. Just read down to the part with heading iFCD "recal"

HCH Bible, by Tarabell

 

I find mine does this even when engine is warm. I find if it happens when I decrease pressure on the gas pedal, but not enough for the car to slip into EV-Mode. The mpg counter jumps in large increments. My joke is that the iFCD is above and beyond the 100mpg mark so it just goes to zero.
It used to freak me out a little at first, now I welcome it.