so i just became a proud owner of a 2003 Nissan #50z with just 34,000 miles... im as happy as a child on christmas morning. But i am having a problem that even the dealer cant figure out.

no matter if the car is warm or cold, as soon as the idle settles it jumps from 550 to 700. all i hear from the engine bay and exhaust is pinging and thumping sounds like misfiring. as this misfiring sound is heard, the idle moves up or down.

the dealer said it needed a tune up so they replaced the plugs and sent me on my way.

problem still occurring so they changed the coil packs with brand new ones.

problem still occurring... i did a fuel pressure check and its fine. so now what do i do?

they said the car has had all its recalls performed to include the cam and crank position sensors.

anyone got any other ideas? im currently running seafoam fuel injector cleaner through the tank to i guess clean out the injectors and see if the problem goes away... any advice or help would be awesome cuz this sound is making me nervous

 

Sounds like a computer problem to me.I'm surprised the dealer did not scan
the car(codes) to see whats up.Is the car stock...no intake mods etc.?
Have you disconnected the battery(negative terminal) wait several hours or
overnight..reconnect?This will allow the computer to "refresh" and learn.
This has worked for me.If that does'nt work,I'd check for a vacuum leak.
Good luck

 

34,000 mi on a 2003?Has the Z been sitting up?Thats some low miles.You may have some moisture/water in the system.I use STABIL for this.But
never had a problem with my Z like this.I also have 2003---bought it new
still have it--70,000 miles.Its like new.

 

Has it been sitting? My first thought was like JCITY...sitting with less than half a tank can result in moisture buildup in the gas tank. Also my second thought was maybe it has been sitting and the only gas in it was less than 91 octane...