blufc3s

On my 07 Z the cruise control is jerky going down hill (decelerating). It maintains the selected speed but is on-off while doing this.
My 03 Z was very smooth decelerating.Has anyone else had this "jerky" issue or know of a fix?
Thanks

zakmartin

Automatic or MT? Miles on car? Any mods to engine? etc. etc. etc.

blufc3s

Sorry for the late reply.
MT, 82,000 KMs (49,000 miles), AEM CAI, but it was jerky before the CAI was added.

zakmartin

It shouldn't be jerky. Do you have aftermarket wheels that are a different size than OEM?

blufc3s

No, stock GT wheels. The tires are oversized though, 285/35-19 rear and 255/40-18 in the front, but within 1% for VDC reqts.

rancor

I have noticed this in my 07 (Auto) also, it will only occur on a steep down hill and it feels like a sudden increase in deceleration. Most noticeably this happens at slower speeds often 55mph (88kph) I cant remember if I have noticed this on a road with a 65mph (105kph) speed limit.

My car has no drive train mods, its had its throttle bodies cleaned and spark plugs and air filters replaced, none of that changed how it acts. It also occurs with both my turning V2 wheels and grand touring V2 weels both with stock tire sizes.

I notice a drop in rpm, about 500, when it occurs. I cant remember if I can reproduce this without the cruse control on. Can you cause the same jerk by going from just barely engaging the throttle to removing your foot completely when going down a hill that will cause this same action in the cruse control?

blufc3s

I never tried to simulate this using the accelerator pedal. If I get a chance before winter sets in I will try it.
On level road or going up hill or a slight down hill, no problem.
It's not a big deal, but curious whereas it never occurred in my 03Z.

rancor

I will try to reproduce it also but as the Z is going into storage and I am getting snow today so it might just need to wait until next year.