High Idle

[Dds1990]

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]

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

[GOLDCYLON]

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]

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...?????

[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...

[GOLDCYLON]

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.

[XfireZ51]

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]

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...:cheers:

[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...

[GOLDCYLON]

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

[zr1eddy]

Hello, I just got my 1990 Z this April and I took it to Mark to have it checked out, mine idled like this and Mark confirmed totally normal for a 90


Sent from my iPhone using ZR-1 Net Registry (https://siteowners.tapatalk.com/byo/displayAndDownloadByoApp?rid=90383)

[Dds1990]

Thanks fellas...as usual great info for a "Newbie"