so when it gets ultra hot my cars rpms seem to be funny on the tach... the first time it happened i was over 6k on the highway at 55mph, it was not the case, but thats what the car said

yesterday the tach read 0 while i was under 20mph... then jumped up to normal spots at speed in a few minutes.

today it was reading low again... but it was actually running lower rpms on the highway. it was nice. so my question is

why is this happening? and also
with stock 17" rims what should my rpms be at when im running 60mph?

 

the tach reading 0 while ur around 20mph or anytime when the car is running means you have a problem, could be the sender unit, wiring or the tach it self. i remember one member here who had this problem that was in middle east i believe due to high heat or something and the dealership ended up replacing the entire cluster to replace the tach

 

Look Here... looks like youre not alone if thats any compensation.

 

Yep, I started that thread. I even had videos to show the dealership about the problem. They ended up replacing my whole tachometer and the clear plastic front panel because they scratched it while trying to replace the gauge cluster.

I have no problem since then. I also haven't parked it directly in the sun either. I suspect the needles getting stuck problem was due to the material inside the needles expanding from the intense heat and causing issues with the motor spinning them.

At 60mph, your tach should read between 2-3k RPM.

 

Agreed that it's most likely just the tach itself. If the ECU was actually getting an indication of zero rpms, it would undoubtedly have have freaked out and thrown a code or something.

 

i was hoping my car would run around at lower rpms now but it cooled off and went back to normally indicated rpms