High Idle - ZR-1 Net Registry Forums

Dds1990 · 08-18-2016

Just recently got the secondarys working on my 1990. I replaced the rubber PCV connector and the secondarys began working and are still working. I am have a high idle ..about 1500 rpm then it will drop to 900 rpm after being stopped for about 5-10 seconds or so. After replacing the PCV connector and first start up I did have a backfire and I did check the MAP sensor vacuum connection and it was fine. Im clear it could be a vacuum leak but where since the secondarys are working?? Could it be a O2 sensor?? As always any and all help will be greatly appreciated....

rush91 · 08-18-2016

It sounds like a vacuum leak, maybe under the plenum. And are your injectors original?

GOLDCYLON · 08-18-2016

If you have checked the MAP hose that's is connected to the MAP Sensor on the rear of the plenum as stated it sounds like the PVC hose or another vacuum hose under the Plenum blew off with that backfire. You will need to pull the plenum to get to it. GC

Dds1990 · 08-18-2016

No they were replaced in June.....There was a vacuum leak at the PCV connection that would not allow the secondarys to work which was fixed. I was under the assumption if the was a vacuum leak under the plenum the secondarys would again not be working...?????

GOLDCYLON · 08-18-2016

Quote:

Originally Posted by Dds1990

No they were replaced in June.....There was a vacuum leak at the PCV connection that would not allow the secondarys to work which was fixed. I was under the assumption if the was a vacuum leak under the plenum the secondarys would again not be working...?????

If its an Idle swing that you are reporting, I'm talking about the vacuum nipples underneath the plenum. The Secondary's will still work unless there is a SES light in the DIC. Is The SES light on?

Does the idle swing from high to low. Or is it high and then the drops to low and remains.

Dds1990 · 08-18-2016

I guess a better question would be where would a vacuum leak causing high idle be at that would not effect the secondarys working properly? The car runs great just when I come to a stop it idles at 1500 rpms then drops to 900 rpms...

XfireZ51 · 08-18-2016

If the idle drops, it may not be a vacuum leak. I see u have a 90 which has a mod to the calibration addressing the Decel Fuel Cutoff routine that does what u are describing.

Paul Workman · 08-18-2016

Quote:

Originally Posted by Dds1990

I guess a better question would be where would a vacuum leak causing high idle be at that would not effect the secondarys working properly? The car runs great just when I come to a stop it idles at 1500 rpms then drops to 900 rpms...

NATURE OF THE BEAST?
Someone (Marc?) correct me if I'm wrong, but I believe that is SOP for a 1990 car. Mine has always done that when coming ro a stop fron hwy speeds, as well as a high idle immediately upon starting that lasts 3-5 seconds before settling down to 850ish.

I read somewhere that this "charming" little feature was adderessed in the 91+ calibrations - Ami's 91 does not do it (tuned by Pete, if that matters).

I've learned to live with it. Nothing to do on startup but wait a few seconds. It gets the oil circulating I guess (and my Ford F150 does the exact same thing on startup).

The high idle, coming down to a stop from hwy speed, does not happen IF I down-shift and engine brake just a little. But, foot off the gas, clutch depressed, and come to a quick stop - I get a high idle for 2-3 seconds.

Initial startup 3-5 seconds @ 2000 rpm; quick stop from speed = 1500 rpm for 2-3 seconds is typical for my 1990 since 2007 when I bought it...

Dds1990 · 08-18-2016

Swings from high to low the stays. Sounds exactly like Pauls 1990...If I downshift it does not do it. Secondarys are working fine. Sounds like its just a 1990 thing...I can live with it...love the car...

GOLDCYLON · 08-18-2016

Quote:

Originally Posted by Dds1990

Swings from high to low the stays. Sounds exactly like Pauls 1990...If I downshift it does not do it. Secondarys are working fine. Sounds like its just a 1990 thing...I can live with it...love the car...

Yep that's normal the way I read it the cars idle was swinging high to low. Mostly high

08-18-2016	#1
Dds1990 Join Date: Jul 2016 Location: INDIANA Posts: 86	High Idle Just recently got the secondarys working on my 1990. I replaced the rubber PCV connector and the secondarys began working and are still working. I am have a high idle ..about 1500 rpm then it will drop to 900 rpm after being stopped for about 5-10 seconds or so. After replacing the PCV connector and first start up I did have a backfire and I did check the MAP sensor vacuum connection and it was fine. Im clear it could be a vacuum leak but where since the secondarys are working?? Could it be a O2 sensor?? As always any and all help will be greatly appreciated....

08-18-2016	#2
rush91 Join Date: Feb 2016 Location: Carterville Illinois Posts: 846	Re: High Idle It sounds like a vacuum leak, maybe under the plenum. And are your injectors original?

08-18-2016	#3
GOLDCYLON Join Date: May 2007 Location: Peoria, AZ Posts: 9,154	Re: High Idle If you have checked the MAP hose that's is connected to the MAP Sensor on the rear of the plenum as stated it sounds like the PVC hose or another vacuum hose under the Plenum blew off with that backfire. You will need to pull the plenum to get to it. GC __________________ GOLDCYLON - 91 ZR-1 #2014 GOLDCYLON - 90 ZR-1 #2794, 4L60e (Formerly Schrade's) GOLDCYLON - 11 CTS-V Arizona State Director 91 WHITE/BLACK #2014. 380 P&P&PCed,Ported Heads, Jeal Long tubes, Corsa Exhaust/FIKSE FM-5s /LED TLs, LED Headlights, Front Wilwood 6 piston narrowlite calipers and rear Wilwood caliper street shop mod,CNCed Coolant Pipes,TPI Cvr,Filter cover,Stainless Bolts, DRM/DOM PROM /ZFDOC mod build #102,DRLs,BMAD with stainless Debris Screen,Coplan Air Blaster, Pioneer APP Radio 4,Brey-Krause HB,Sub Bar,Fire extinguisher seat mount,DRM Coilovers,LEDs everywhere,Compass mirror (orange),V1 DIC hidden display, Homelink sun visor, Carbon Fiber top x3 and APSIS Carbon Fiber interior, APSIS CF Steering Wheel/NAPA Leather, Banski trailing arms, Guldstrand front suspension,urethane bushings from Prothane (total suspension) ZFDoc drive shaft safety loop, raptor shift light (orange),AO engineering louver front plate, Console seat cushion, 96CE seats with black custom Sheepskins, ss billet catch can,Viper remote entry/alarm,Cragar Rear Louvers,LED side louver lights, Dewitts Radiator with SPAL fans and a Woods 160 T-Stat 90 RED/BLACK #2794. 4L60e Automatic Stage V by RPM Transmission, TCI Dedicated TCM, OBX Stainless Headers, Corsa Exhaust, SAN Secondaries and Haibeck PROM, Exotic Muscle Coil overs, LED Interior Lights, LED Tail Lights, LED Headlights, 94 Sport seats with black custom Sheepskins , Cragar rear louvers, GS Front calipers, Banski Trailing arms, APSIS Carbon Fiber steering wheel, Front and Rear Baer Eradispeeds, DRLs, Guldstrand front suspension,urethane bushings from Prothane (total suspension), Dewitt's Raditor with Dual SPAL fans and a Haibeck 170 T-Stat 11 RED/GREY CTS-V

08-18-2016	#4
Dds1990 Join Date: Jul 2016 Location: INDIANA Posts: 86	Re: High Idle No they were replaced in June.....There was a vacuum leak at the PCV connection that would not allow the secondarys to work which was fixed. I was under the assumption if the was a vacuum leak under the plenum the secondarys would again not be working...?????

08-18-2016	#6
Dds1990 Join Date: Jul 2016 Location: INDIANA Posts: 86	Re: High Idle I guess a better question would be where would a vacuum leak causing high idle be at that would not effect the secondarys working properly? The car runs great just when I come to a stop it idles at 1500 rpms then drops to 900 rpms...

08-18-2016	#7
XfireZ51 Join Date: May 2007 Location: Chicagoland, IL Posts: 9,696	Re: High Idle If the idle drops, it may not be a vacuum leak. I see u have a 90 which has a mod to the calibration addressing the Decel Fuel Cutoff routine that does what u are describing. __________________ [SIGPIC][/SIGPIC]Former Membership Chairman Former ZR-1 Registry - BOD 1972 Corvette 4speed base Coupe SOLD long time ago 1984 Corvette Z-51/4+3 SOLD 1992 Corvette ZR-1 Aqua/Gray #474 SOLD 1992 Corvette ZR-1 Black Rose/Cognac #458 2014 Honda VFR Interceptor DX

08-18-2016	#9
Dds1990 Join Date: Jul 2016 Location: INDIANA Posts: 86	Re: High Idle Swings from high to low the stays. Sounds exactly like Pauls 1990...If I downshift it does not do it. Secondarys are working fine. Sounds like its just a 1990 thing...I can live with it...love the car...