Fzj80 high idle issue!

Joined
Apr 3, 2022
Messages
3
Location
Australia
Hey all first time poster here

I have a 1994 fzj80 Manual and I have been chasing a high idle issue for over a year now. When first started in the morning it runs perfect, no high idle, and then one you start driving and it warms up, or revving it at all, it will high idle between 1500-2200. Eventually it will slowly try to return to idle but it’s no different with aircon on or off, even with the iac unplugged it does the same. I have replaced the ecu, used multiple second hand iac, vaf, tps, removed all vsv and other valves from intake plenum to eliminate vacuum leaks etc. hopefully I explained it enough so some clever Bugga can help, thanks🙂 (oil light is the sender being buggered along with oil pressure gauge😬)

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Joined
Apr 14, 2016
Messages
2,364
Location
Oregon
Did you replace every single vacuum hose, test the vacuum switching valves, and verify that the passages through the intake are clear?
 
Joined
Apr 3, 2022
Messages
3
Location
Australia
Did you replace every single vacuum hose, test the vacuum switching valves, and verify that the passages through the intake are clear?
I had the intake off to clean the throttle body and seal the gaskets where the two pieces of intake plenum meet, and I went through all the vacuum hoses and removed the vsv valves, I read a thread on here about people doing it and it being fine so I did the same, with No improvement
 
Joined
Dec 8, 2006
Messages
11,033
Location
New Jersey
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www.sdsysdesign.com
I haven’t replaced it no, I have checked the throttle cable however and it doesn’t appear to be binding or getting caught
There should be slack in the cable when the throttle plate is in the idle position. If your cable is too tight, it might not be letting the throttle plate close all the way. Or there might be some crap blocking the mechanical operation of the throttle plate. Make sure it moves freely throughout its range.
The ISC only comes into play when the TPS senses that the throttle plate is closed. Then the ECU will push the ISC for proper 650 rpm idle speed, assuming all the other sensors are working correctly.
 

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