Egr
 

how can i tell if EGR is bad on Z34? what else can cause it to idle REAL fast--like i had my "foot stuck in the carburetor"? it's not vacuum leak, not IAC valve--it scares me, 'cause i'm afraid i'm going to slam into something one day.

high idle can be caused by several things.
1. A vacuum leak.
2. Sticking or faulty Idle Air Control Valve (IAC).
3. Carbon build-up in the throttle body bore and plate.
Always have the system scanned for codes first.
Or the EGR calve and also a plugged Catalytic converter.
Keep in mind this stuff that you replace can be faulty as well, some of it isn't made to last.
Vacuum Leak: On a fuel injected engine a vacuum leak will cause a high engine idle. ... Malfunctioning Throttle: A malfunctioning throttle system can cause both a high idle as well as an engine stall. A dirty air intake or cracked air intake tube is often the culprit.

Is it a constant "foot in carb" situation or not all the time? Unlikely but possibly throttle cable stuck. Happened to me.

THANKS so much for your reply. you bring up a couple of things i was never told. How would one check for a cracked or dirty intake

Not constant---usually does it when i crank it. sometimes i have to crank it and cut if off FIVE times before it idles at the right speed.

but SOMETIMES when i'm driving, like real slow thru a parking lot, all of a sudden it goes WIDE OPEN, tach up to 2500. it's hard to stop when the motor is going that fast.

Pop it into Neutral and shut it off then. I am thinking your throttle cable may be the culprit I would check that for sure.

I should have added here why this happened to me.. My cruise control engaged and pulled the cable to WOT.. I mean, the cruise control was off (no green light on, on the button) and no indication on the dash.

i haven't used Cruise control in ages. never get on a road where it'd help. And i've never had any light come on when i used it. ?????

when i got my car it only had 71K miles, so don't seem likely the lights would have quit by then.