I have a 83 Non-T car that mysteriously the idle went to 1200 and is surging to 2000 or so mysteriuously. I have checked for Vac leaks , replaced the Idle Air control valve on top and it still does the same thing. I have owned 4- 280's and have never had this issue. I have read where it COULD be one of several things from AFM to O2 sensors ect ect. my question is has anyone actually HAD or seen this issue and what exactly fixed it ?
Thanks in advance to any Real solutions not guesses..

 

Welcome to ZDriver!

Hum... it's pretty hard NOT to guess with a very basic / general description over the internet... it would be easier if you could give more detail.

I would start by checking all the things you've already discovered COULD be the problem: Timing, AFM, idle screw, and vacuum leaks are the main cause of high idle.

If you haven't do so yet, I suggest buying the Haynes manual or download the FSM for free at www.xenons130.com/reference

 

I know it's hard over the Net..and it could be a number of things.. Just wondered if anyone had or seen this exact issue high idle at cold start and surging or revving between 1000-2000 non stop doesnt go away ..what was their fix for similar issue.. As a process of elimination to back diagnois before I just start replacing things that it could be...

 

Looks like I should have posted in the General forum.. but thanks to Nismo and anyone who sees this post to respond.

 

I have a 83 NoN -T car . I have had 4 280zx's and have never had one have this issue .. The car wasa running fine but one day last week Upon cold start the idle is about 2300 upon warming up it starts surging to over 3000-3500 on its own. I have checked for vacum leaks and cant find any Replaced the Air Idle Control Valve cleaned the MAF meter & throttle body .. No difference.
I know it could be alot of different things.. As a Z owner for 20 yrs I have never seen this symtom or issue. Has anyone else? If so what fixed it? In the meantime I'll keep searching. Thanks in advance for any responses..

 

If there is no vacuum leaks it's directly related to a malfunction of mechanical parts in the Ign distributor or air flow meter butterfly open close function. It can also be at your trottle linkage. Try looking at that and let us know when it's fixed.

 

[QUOTE=Black&Gold83Z;306866]I have a 83 NoN -T car . I have had 4 280zx's and have never had one have this issue .. The car wasa running fine but one day last week Upon cold start the idle is about 2300 upon warming up it starts surging to over 3000-3500 on its own. I have checked for vacum leaks and cant find any Replaced the Air Idle Control Valve cleaned the MAF meter & throttle body .. No difference.
I know it could be alot of different things.. As a Z owner for 20 yrs I have never seen this symtom or issue. Has anyone else? If so what fixed it? In the meantime I'll keep searching. Thanks in advance for any responses..[/ After you have checked all the possibilities i mentioned before and have no avail it has to be a bad BCDD valve. I'm almost sure it will be that. Good luck with it.

 

Merged threads.

x2... BCDD.

 

What happens when you take the oil cap off when it's idling?

 

I truely appreciate your suggestions..and will impliment a diagonosis as soon as I can.. hopefully a day or 2.. will get back with what I find..

 

Zen what does BCDD stand for never herd of it? Thanks Cary

 

I took the rubber tube off the AFM where I can see the AFM inlet door with a mirror when the car starts surging I can see the door oopening and closing with the surging. Not sure if that is a falty AFM symtom or if something else is causing the AFM door to open and close. Think I am going to buy a new AFM and put it on and see if it fixes it.. if not I know I will need a AFM in the future and know that is not my problem..

 

BCDD = Boost Controlled Deceleration Device.

I wouldn't blow $200-$400 for a new / reman AFM when you could adjust (fix) it yourself if it were the problem.

https://www.zdriver.com/forums/240z-280zxt-s30-s130-tech-tips-275/js-how-rebuild-your-afm-15277/

 

I hope the door moves with the surging!

It's pretty easy to rebuild the AFM. Did you make sure the connector for the AFM was seated properly? Missing clip? Corrosion on the connectors?

 

There should be a single vacuum line running from the top of the intake to underneath the manifold to the BCDD.Just pinch the hose off and see if the idle goes back to normal.If so just block off or remove and plug both ends.Mine runs fine without the BCDD with no problems.

 

Thanks again guys !!
The door on the MAF is flapping with the surging..Not surge if thats a bad AFM or is some thing else causeing the AFM to open & close..I am borrowing a AFM from a friend and will blt it on as a process of elimination as well as the other suggestions.
THANKS again will find the demon sooner or later !!

 

Didnt make a difference still very high idle & surging .. will have another AFM next week to try..
THANKS !!

 

Will put it on today and see if thats the fix !

 

Well put on another MAF and no change ..still super high idle & surging after warm up.. will look at the other suggestions now .. process of elimination will have several new replacement parts when this fix is done..if I dont give up and haul it to the Z clinic here in austin.

 

In case you missed this:

and this...


Sounds like a vacuum leak to me.

 

Me too Nis..so I'm gonna keep looking in no so very obvious vacum areas..
When I did disconnect the vac hose from the mani to the BCDD nothing happen ..as I remember..will try it again..If it was working I would think it should responed? Hmmmm..

 

Did you take the oil cap off yet?

 

I did it today.. it does bring the idle down.. but when I gave it some throttle it gos back up to high and stays there..I have a friend gonna come out tonight who was a pro mechanic on US domestic cars ..Not a Z guy and help me mess with it over a few beers....

 

A system is a system is a system...... he'll be able to help you out. Still sounds like a vacuum leak....

 

Just diagnosied to have a Bad BCDD Valve so you guys get the Prize of Knowledge & Know How..After having 4 of these cars (and thought I pretty much knew the basic componet failures of these cars) I learned alot from you guys and my friend the ex Pro Domestic Mechanic ! Now to find one and I will install myself !
If I can help you guyz in Any way give me a shout out !
Will follow to confirm it !
THANKS AGAIN !