1997 280z rev fluctuating between 2000-3000 rpms

[evanlowe98]

so i was driving down the road last night about 2:30am and i noticed my head lights weren’t working only my high beams but didn’t care that much just wanted to get home. so i keep going and i look at my AFR gauge and it was a little lean so i took it out of gear and put it in neutral and my RPMS jumped to 3000 and then started fluctuating between 2500-3000 and wouldn’t stop so i pulled over looked for vacuum leaks and found nothing. kept look and couldn’t find anything so i pulled the wire on the AFM and it made my RPMs drop about 1000 but kept fluctuating. i can’t figure out what’s wrong plz help!

 

 

Sent from my iPhone using Classic Zcar Club mobile

[siteunseen]

Take the black cover off the AFM and make sure the sweep vane is working freely.  Cobwebs and what not get in there.

Very helpful info here thanks to 240260280 aka Blue's Tech Tips.

http://atlanticz.ca/zclub/techtips/EFI&fuel.htm

Edited October 28, 2017 by siteunseen

[evanlowe98]

yes the AFM is working properly i already have the cover off cuz i have messed with it for more fuel. i pulled the throttle position sensor and ohm tested it and it read an open circuit on one side so i’m going to get a spare and see if that fixes it but i don’t know.


Sent from my iPhone using Classic Zcar Club mobile

[siteunseen]

I don't know about open circuits on the TPS but I bent mine with my fingers to make contact at idle and wide open throttle.

I'm hoping to help, not make you mad so forgive me if I'm saying stuff you already know. 

http://atlanticz.ca/zclub/techtips/tps/index.html

[Zed Head]

8 hours ago, evanlowe98 said:

 i took it out of gear and put it in neutral

Is it an automatic transmission?  With a manual you can just push the clutch pedal.

Engine RPM is controlled mainly by air allowed in to the intake manifold.  You might have some kind of intake system leak.  Automatics have some vacuum actuated mechanisms, that can cause problems.

[evanlowe98]

Is it an automatic transmission?  With a manual you can just push the clutch pedal.
Engine RPM is controlled mainly by air allowed in to the intake manifold.  You might have some kind of intake system leak.  Automatics have some vacuum actuated mechanisms, that can cause problems.

manual and no leaks on intake at all use carb cleaner and can’t hear anything. so no leaks.


Sent from my iPhone using Classic Zcar Club mobile

[Zed Head]

Is your BCDD still attached?  They are known for causing idle speed problems.

You should put your car and engine details in the first post or your sig.  Not clear what you're working with.  It might be a 1977 (right?, not 1997) car, but the engine could be a transplant.  Plus you have an AFR gauge, which implies that you've done some modifications.

[evanlowe98]

Is your BCDD still attached?  They are known for causing idle speed problems.
You should put your car and engine details in the first post or your sig.  Not clear what you're working with.  It might be a 1977 (right?, not 1997) car, but the engine could be a transplant.  Plus you have an AFR gauge, which implies that you've done some modifications.

yes a 1977 and yes it’s boosted on a na block and after market heads and cams. no BCDD valve and no smog. AFR gauge is for making sure i don’t run lean in boost.


Sent from my iPhone using Classic Zcar Club mobile

[Zed Head]

8 minutes ago, evanlowe98 said:

yes a 1977 and yes it’s boosted on a na block and after market heads and cams. no BCDD valve and no smog. AFR gauge is for making sure i don’t run lean in boost.
 

Did you do the work, or buy it that way?  There are people here who can add some ideas, but this is "classic" Zcars. com, not what you're running.  I don't think that "aftermarket" heads exist for the L6 block, except for Derek's.  If you bought one of those you should probably be on hybridz.org.

But, back to the the basics - describe the engine details, and how it got that way.  Are you running a ZX engine management, or a cobbled  77 EFI system?  The stock Nissan turbo, or "aftermarket"?  "Smog" means what?  Hoses not understood or actual systems described in the Emissions chapter of the FSM?

We know a lot about the Nissan made stuff, but once somebody gets in and starts tweaking, it can get weird.

[evanlowe98]

Did you do the work, or buy it that way?  There are people here who can add some ideas, but this is "classic" Zcars. com, not what you're running.  I don't think that "aftermarket" heads exist for the L6 block, except for Derek's.  If you bought one of those you should probably be on hybridz.org.
But, back to the the basics - describe the engine details, and how it got that way.  Are you running a ZX engine management, or a cobbled  77 EFI system?  The stock Nissan turbo, or "aftermarket"?  "Smog" means what?  Hoses not understood or actual systems described in the Emissions chapter of the FSM?
We know a lot about the Nissan made stuff, but once somebody gets in and starts tweaking, it can get weird.

don’t know the kind of heads or cams. yes i did the work setting up the turbo and everything. no car is not on a stand alone or piggy back. on 1977 ECU and FSM smog as in emissions. it’s a 59mm turbo on the stock 83 turbo manifold. AFR’s reading 10.9 at idle and 12.3 at WOT all read fine. i wasn’t in boost or anything when it freaked out. just happened changing gears. and yes still the stock EFI system. the AFM i have tweeted for more fuel pressure so it doesn’t lean out in boost. boost is set at 15 PSI. Any other questions about the car or work down?


Sent from my iPhone using Classic Zcar Club mobile

[Patcon]

I think you are going to have a real challenge getting it properly tuned using the factory EFI. You need more resolution in your maps and the shape of the maps will be different than what the stock system can provide. I use the term "Maps" loosely as I don't know that the stock ECU even really uses a map

BTW your numbers are really rich...

[Zed Head]

Edit - this post is blunt, but true I think.  No offense.  You really do need to learn the details.

You're in way over your head.  You made it work, boost happens and it probably goes faster, but fine tuning requires detailed understanding.  How about your boost controller?  Maybe it's on the fritz.

Without all of the details of your "turbo" system people can just throw out ideas.  But you're not really processing the help you're getting.  You just repeated my words back to me on my smog question, but didn't add any details.  "FSM smog"?  You're going to have to study up on how turbo engine management works, and keep cobbling away on your NA system.  We'll throw ideas at you as you give more details though.

Nothing good happens after 2 am. 

Edited October 29, 2017 by Zed Head