HT4100 4.1, 4.5, 4.9 Discussion, How to adjust idle speed on '91 Eldorado 4,5l V8 ? in Cadillac Engine Technical Discussion; Hello,
Excuse me for my approximative english, because i'am french...
I have bought last week an 1991 Eldorado with 4,5l ...
Automobile(s): 1995 FWB 100,*** miles CURRENT. 1991 Seville 175,000 SOLD
Re: How to adjust idle speed on '91 Eldorado 4,5l V8 ?
This is for 4.9 engine, but probably works on 4.5 as well
Here is the ISC motor adjustment procedure for 4.9 liter engine outlined by the Guru. It should be the same for 94 Northstar. The gap is probably 0.060".
"Hold the throttle lever open manually to get the RPM to about 2500 or so. Simultaneously depress the plunger on the idle speed control motor so that it starts retracting. Keep forcing the plunger to retract until it fully retracts and stops. Disconnect the wire connector to the idle speed control motor to "freeze" it.
Return the throttle to the closed bore idle position. Use that torx screw that you have been jacking on to lower the idle to 450-500 RPM. 450 is the desired setting. The idle should come down to 450 and there should still be clearance to the ISC motor plunger. Nothing (like cruise control or throttle cable) should keep the throttle lever from going down to the 450 idle point.
Idling at 450 with the ISC motor fully retracted turn the plunger until there is a .030 gap between the plunger and the throttle lever.
Check the cruise link while at the 450 idle point. It should just be barely snug with a tiny bit of slack in the link. Make sure that there is a little slack when you adjust it. There MUST be some....just a little but some slack.
Plug in the idle speed control motor connector and cycle the key off.
Disconnect the battery negative cable for 60 seconds to erase any idle learn offsets that have been stored. Cycle the key on for 30 seconds and then off. Wait 60 seconds. Cycle the key again."
If there is still no gap, unscrew the plunger and cut it or try the plunger from th eold motor. That's what I had to do with one of three ISC motors I installed on my 4.9 in ten years.