76 280z high rpm
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IdahoCoug
- Posts: 1
- Joined: Mon Jun 08, 2020 2:34 pm
- Car: 1976 Datsun 280Z
1977 Datsun 280Z 2+2
1993 Nissan 300ZX Turbo
76 280z high rpm
Hi, I am new to this forum. I have a 1976 280Z and my problem is while driving and coming to a stop the idle stays high for a few seconds before coming back down to normal. Is this a problem with my AFM setting? Any help is appreciated?
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AZhitman
- Administrator
- Posts: 71063
- Joined: Mon Apr 29, 2002 2:04 am
- Car: 58 L210, 63 Bluebird RHD, 64 NL320, 65 SPL310, 66 411 RHD, 67 WRL411, 68 510 SR20, 75 280Z RB25, 77 620 SR20, 79 B310, 90 S13, 92 SE-R, 92 Silvia Qs, 98 S14.
- Location: Surprise, Arizona
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Re: 76 280z high rpm
Welcome aboard, Idaho!
A few possibilities, in order of commonality:
1 - Throttle cable linkage binding. Easy to test, pop the hood, run engine (by hand) at 3-4k RPM for a few, then drop the linkage. See if it remains at high idle, and if so, try to manually decelerate it. If that's the fix, lube the cable and throttle linkage.
2 - AFM contact points can get funky and sticky. You may have to do a search on the process for cleaning them, it's been over a decade since I messed with one.
3 - On deceleration in the L28, manifold pressure surges and causes the RPM's to stay high. The factory installed a "Boost Controlled Deceleration Device" (BCDD). Allegedly, they have been known to fail. I have heard that some Z owners remove this piece completely with good results.
4 - Vacuum leak (although this should maintain consistent high idle, not just after stopping).
Keep us posted!
A few possibilities, in order of commonality:
1 - Throttle cable linkage binding. Easy to test, pop the hood, run engine (by hand) at 3-4k RPM for a few, then drop the linkage. See if it remains at high idle, and if so, try to manually decelerate it. If that's the fix, lube the cable and throttle linkage.
2 - AFM contact points can get funky and sticky. You may have to do a search on the process for cleaning them, it's been over a decade since I messed with one.
3 - On deceleration in the L28, manifold pressure surges and causes the RPM's to stay high. The factory installed a "Boost Controlled Deceleration Device" (BCDD). Allegedly, they have been known to fail. I have heard that some Z owners remove this piece completely with good results.
4 - Vacuum leak (although this should maintain consistent high idle, not just after stopping).
Keep us posted!
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