Idle speed again
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Joined: Dec 2002
Posts: 83
Likes: 0
From: Everett WA
Idle speed again
My 87 is idling around 1200 but will back off to around 900-1000 after about 30 seconds (even when hot). I've replaced the intake manifold gasket, IAC, Oxygen sensor, EGR hose, EGR temp sensor, vacuum check valves, t, checked all obvious vacuum lines. What else could cause the thing to idle so high? I suspect I could have a problem with the vacuum lines at my AC programmer, but haven't felt like torturing myself again to go under there. I've looked in the archives, but can't seem to find any clues.
Melting Slicks
Joined: Aug 2003
Posts: 3,380
Likes: 388
From: Lakeville MI
Re: Idle speed again (87Vert)
The idle control has two operating modes, An open loop mode intended for cold start idle, which simply controls the IAC position as a function of coolant temperature. There is also a closed loop pid controlled idle which controls the idle rpm as a function of coolant temperature, with a typical setting of 500 rpm for normal coolant temps.
Most likely the throttle itself is open way too much, and the IAC cannot close-off enough to compensate properly. Get an OBD1 cable available from AKM electronics and others and run datamaster or EFIlive software to get a look inside at what's going on. Another option would be to build a simple 160 baud interface and use WinALDL software. You should be able to find lots of info in the Scan and Tune area once you get that far. The calibration of the MAF also plays a role with respect to mixture control and BLMs since there is only a limited range of self compensation.
In my experience it is nearly impossible to get a good idle when working blind, by just tweaking the throttle stop screw, and/or tps sensor, etc.
Most likely the throttle itself is open way too much, and the IAC cannot close-off enough to compensate properly. Get an OBD1 cable available from AKM electronics and others and run datamaster or EFIlive software to get a look inside at what's going on. Another option would be to build a simple 160 baud interface and use WinALDL software. You should be able to find lots of info in the Scan and Tune area once you get that far. The calibration of the MAF also plays a role with respect to mixture control and BLMs since there is only a limited range of self compensation.
In my experience it is nearly impossible to get a good idle when working blind, by just tweaking the throttle stop screw, and/or tps sensor, etc.
Instructor
Joined: Jun 2003
Posts: 128
Likes: 0
From: tampa fl
Re: Idle speed again (87Vert)
As I worked my way through all the issues inherited with the wifes 85, one thing on the forum made mine work properly. After numerous attemps to set the base idle, one of the senior members advised that during the procedure the ETS should be disconnected also. Well today because of this advise it's running great and I quit losing sleep and hair. Hope this helps!
ROCKY85
P.S. Still have alot of sensor issues but thats for another case of beer!
ROCKY85
P.S. Still have alot of sensor issues but thats for another case of beer!
