Deaded Idle Surge?
 

This evening I was driving my 90 Z back from the Dallas Auto Show. Everything was golden until I pulled off the highway and up to a stop light. The idle stayed at about 2000 RPM for 20 seconds or so, then, in steps, dropped to 1200, then 750, then 600 or so where it remained for the rest of the drive home (all on secondary streets). It hasn't done this before, but I really haven't driven it enough to know what is normal. Any comments/suggestions? :dontknow:

Jim

Re: Deaded Idle Surge?
 

Check your vacuum hoses. Usually they are the culprits. One is probably cracked or hanging on by a thread. Good luck and let us know what you find. :handshak:

Re: Deaded Idle Surge?
 

Check the PCV "F".

Re: Deaded Idle Surge?
 

Aslo are you running the original PROM? Gm released an update to the prom due to this surging problem but the previous owner may or may not have gotten it fixed. If this is the first time you have experienced this then as the other members have already stated the PCV hose and even a dirty IAC can cause this as well. If you had poped a hose under the TB the idle would never fall.

Re: Deaded Idle Surge?
 

Just in case you may want to see the TSB on the PROM update it's over at the netreg site.

http://www.zr1netregistry.com/bulletins/476503-1.jpg


The only issue now is this replacement PROM seems to be NLA. I'm not 100% positive on the NLA, but when I run the P/N nothing comes back. I get the "no such part number" message.

I'd check for vacuum leaks first and you can tell if the PROM was done by hooking up a scanner as it will give the PROM ID# after you verify the VIN #.

:cheers:
Tom

Re: Deaded Idle Surge?
 

maybe someone could copy that updated prom and post a file so everyone could burn it because I also know that its no longer availabkle from gm

Re: Deaded Idle Surge?
 

Here it is. I found a BRXB which looks to be a 91 ZR-1 cal as well. Don't know much about it but maybe some of the ZR-1 gods can chime in.
:cheers:

Note: I make no guarantees for the bin. Use at your own discretion. If somebody tries it out, let us know if it works.

Re: Deaded Idle Surge?
 

This should have been a recall and not just a Service Bulletin ! Hard to find an owner of a 90 or 91 Z with the original Memcal that hasn't had high idle problems and hard hot cranking. :confused:

Re: Deaded Idle Surge?
 

I've got a Haibeck (sp) prom in the car. Still have the original in a bag. I haven't had a chance to look at the vacuum hoses and just bought a set of manuals off ebay. I haven't driven the car since bringing it home from the Dallas Auto Show.

Jim

Re: Deaded Idle Surge?
 

Ok that answers that Jim your prom is ruled out as the culprit. So a dirty IAC or a vac hose maybe the issue. Did the car backfire upon a startup recently? Normally that event occurs before the PVC hose blows off behind the plenum next to the firewall. As will cause the idle symptoms