For the vacuum leak, check the bolts on the intake manifold top plate for tightness - I have seen them finger tight on virgin CFI's... Also, see how much play or movement you have in the throttle brackets on the throttle bodies. If both are not fairly tight, this could  likely be your vacuum leak and you'll need to get the TB's bushed. This is a normal problem on CFI's with 60k plus miles - even seen it on one with 45k miles. My 82 had 90k and bushing took care of the high idle issues for good.

Good luck!
  Phill's Vette2010-11-13 13:44:50

Hi Chip and Phill.  I hope it turns out to be something else.  I've pretty much ruled out the TBs.  I've hit all around them with carb cleaner with not a bit of change in the idle. I have torqued the bolts on the TB/Intake top plate and the TBs and no leaks around the seal.  I decided to take it into town this AM.  Ran great.  Idled fine.  Took about 35 mins to get to work.  It was a bit cool but, 75 mph to the outskirts of town then 35-40 in between the lights for 10 minutes.  No O2 code or excessive idle.  Parked in my spot and the idle was right at 800-900 rpm. 

On the way home in the PM,  I stopped about mid-way and it was idling at 1700 rpm.  A few minutes later after I got off the throttle from about 65 mph the check engine light came on.  Turned out to be the O2 code 13. For that code to set the TPS should be not at idle. There could be something intermittent in the ECM. A vacuum leak should be pretty much always leaking - Right?  I have many years experience in component level electronics as a repair technician.  I'll have to look at the ECM closely before I replace it.

BTW - Chip is that the original gray interior? Looks great.  Phill How much clearance to you have off the ground?  Both are good looking rides!
Thanks for the thoughts.  I'll be back into it tomorrow.
Keith
 

Sorry for the late reply I forgot to subscribe and have been off the board for awhile. I live 5 miles west of Sandario on Manville. The offer is still good to meet with you and see what the scanner is saying.
I'll PM my cell #.

Thanks Philip,
I have to go into town in the morning but, I'll give you a call after I get back to the area.  Thanks for the offer. 

Keith

Keith,  thanks for the compliment but no,  its not the original interior.  I replaced the interior about 5 years ago.  

Thanks to all that have offered their opinions and suggestions.  I got together with Phillip and used his analyzer and experience to come up with a game plan.  The O2 sensor is producing a voltage a little lower than what I have read as spec. I think a heated O2 sensor will help keep it in closed loop.  It drops out of closed loop when I decelerate from a cruse and the O2 sensor cools a bit.  I've learned from the folks here and at the CFI Vault Forum that only in closed loop mode does the regulation of the mixture take place.   The TPS, CTS and MAP are all working.  The linkage to the TBS shows wear and the shafts have worn the lining of the connecting rods so allowing vacuum leakage to the TBS.  I really did not know how to check that.  I still think I'll remove the computer and look through that for cracked solder joints and clean the EProm socket and general electronic servicing that I know. 

The car still performs very well and I will look for a place that can do the repairs to the TBS.  I'm not in that much hurry. So, I will have to park the ride for a while this winter.  Thanks again for all the support from the members of C3VR and Philip and Chip. 

Keith

Keith one thing that can be done is to remove the IAC solenoids and clean any carbon build up from the pintle and in the air passage. We can do that in my shop if you like as soon as I get the Nova on the road again.

Thanks for the offer Philip.  It is nice to know you and thanks for the help.  I drove down to the pecan festival today and it was nice to open her up on I-19.  Speed Limit 75 - traffic flow 85.  There were pick up trucks and SUVs passing me at 85!  The car performs great on the road.  The idle is irregular and for the most part is somewhere between 1000 and 1200.  It did get stuck up at 1500 rpm so, I have decided to look into the brushing service from DCS.

              http://www.crossfireinjection.net/about_us.htm

I think it will be a while before I send them in but, I have an inquiry in with them.  I will let you know what I find out.  One can send in the cores and get serviceable replacements or request return after service of my original cores. I have not checked for matching numbers on this car but, the previous owner gave me all the information he received from the original owner.  The biggest thing replaced was one of the bronzed T-Top after a break-in event.

I thought I had a place to send in the complete units but, does not look that way on my recent searches.  I'm still reading and learning on the CFI Vault page.  The DCS site also has some information available under the "How to" section.  I will post what I find out.  I'm thinking that cleaning the IAC won't hurt.  Thanks again.

The DCS site was informative. Some nice products and services offered too.