My 280 had a bad catalytic converter and had the same symptoms. Be careful though. I took mine out, put in a straight pipe. Ran faster than ever, but blew the rings because there was no backpressure.
If you remove it and it runs better, be sure to put a replacement in it's place.
Steve
HEy guys, its the Telrenners again :-)
>
> The hesitation on the Z is getting worse. When i push on the gass, it
> starts lowering revs as if i had cut off the gas for a few seconds, then
> sometimes will pick up. WE determined it is nto the fule system. WE have
> it narrowed down to 3 parts (we think):
>
> Timing chain is worn out : WE are going to look at it tomorrow and see if
> that is it. Hopefully so, seems to be the easiest fix
>
> ECU dying: This is the most expensive option, but also seems likely,
> becuase if we are moving, i can set it to accessory breifly, and then turn
> it back to run, and it will drive well for about 5 minutes.
>
> Ingition System: Under the Cap and Rotor (which we replaced, along with
> wires and Plugs) we were also wondering if this might be wearing out
> instead of the timing chain.
>
> Any suggestions from the Z Experts?
>
> Thnxz
>
>