01-06-09, 10:11 PM
I just purchased a 1992 DeVille w/ 66,700 miles on it and it's having trouble starting, it idles rough and when I acclerate it's a little jumpy and hesitant. I ran the codes and got a E30 which is for the ISC motor. Is there anyone in the West Burbs of Chicago that I could pay to help me install this new motor. I don't think it will be to hard, I just have no garage and am not the most mechinically inclined.
01-07-09, 12:46 PM
Before you install the new motor. try resetting it. You will need two people for this. Have one person sit in the car and be ready to turn the key off when you say so. With the car running, the second person needs to open the open the throttle body a little to make the engine run faster. While doing this you need to push down on the plunger for the ISC motor. You will feel the ISC motor retract as it tries to slow the engine back down. When the ISC plunger is fully retracted have the person in the car shut it off. Unplug the ISC motor (the connector should be right behind it) and plug it back in. This will reset the motor position in the computer and may fix the problem. I was having the same issue with my car and this worked and saved me $80 (price of new ISC motor).
If that doesn't work I'd be happy to help you with it.
01-07-09, 01:57 PM
Is the motor and plunger 1 piece? Is it at the front/or back of the engine?
01-07-09, 05:32 PM
It is right at the front. My car is in storage and under a cover but here is an old picture that I dug up and zoomed in so you can see what components I am talking about. Just play around under the hood with the car running and you will understand what needs to happen to reset the ISC motor. Moving the throttle body clockwise will increase engine speed. While doing that push down on the ISC plunger (just enough to trigger the switch that is in there, do not force it down) and you will feel it start to retract.
I don't think that is your problem though. Sounds more like you just need a tune up (new spark plugs, wires, cap, rotor and coil). You may also have to clean out the EGR valve. It is very common on the 4100-4900 for the EGR to become plugged with carbon. You may also have some dirty injectors. Go to the store and buy some STP Fuel Injector Cleaner or preferably Fuel System Cleaner. Pour that in with some Shell or BP premium fuel next time you fill up. Only do it once though because if you use the stuff continually it will cause lots of carbon build up in the engine.
01-07-09, 05:59 PM
Ok, when I move the throttle body to increase the rpm's, should i increase it to what sounds to me like the correct rpm idle speed, hold it there and then push in the silver plunger contact or am i doing both of these at the same time? I guess what I'm asking is, does the car automatically know the correct setting for the idle rpms/speed or am I setting the idle rpm/speed by moving and holding the throttle body?
Awesome pics man! That really helped me out!
01-07-09, 06:14 PM
1 more thing, is the throttle body supposed to be touching the ISC plunger contact at all, during idle or when its turned off? Mine isnt, which makes me think the TB is to far counter clockwise because the plunger contact isn't far enough out of the ISC motor meaning the rpm's arent' set as high giving it the stalling feeling or rough idle. Do you follow?
01-07-09, 10:54 PM
Yes, whenever the car is idling it should be hitting the plunger. When you give the car gas the plunger will move out a little bit and then when you let go of the throttle body it should hit the plunger and then slowly go back down to the correct idle speed. Now that you say it does not always touch it make me think that the motor may actually be bad. Check the connection and make sure it is actually connected. It is rare for the motor to take a dump, its one of those things that just doesn't break very often. Every now and then I get the same code on my Fleetwood but the ISC is fine.
To answer your first post you should do both things at the same time. Let the motor retract all the way and then have someone shut the engine off. Disconnect the electrical plug for the motor and clean it with some electrical cleaner. Hook it back together and start the car. You may have to let it sit in the "run" position before actually starting the engine so the motor has time to extend back to where it should be. As a note, you may have to reverse the steps, I can't remember. You may have to have someone disconnect the ISC motor while it is fully retracted and the car is still running, then have the second person shut the engine off.
The car does not know exactly where the ISC should be at to make the car run normal. It constantly adjusts itself to make it run right. There is a little switch at the bottom of the plunger (inside the motor) that tells the car when the throttle body is touching the plunger. If it is idling too high and the car senses that switch is activated it will retract the ISC and slow the idle speed. It should do the opposite when the car is not idling. If that switch is not depressed the ISC will fully extend and wait for the throttle body to make contact with the plunger. This is why you need to "reset" the motor. It may have "forgotten" where the fully extended position is.
You may have to have someone disconnect the ISC motor while it is fully retracted and the car is still running, then have the second person shut the engine off.
This is the correct way to do it. After it is retracted and unplugged, adjust the gap between the ISC plunger and the throttle linkage to .060.
BTW, this thread should probably be in the 4.1/4.5/4.9 section, but I'm not a mod here so I can't move it.
07-22-09, 10:50 AM
Can anyone in the city or burbs help me adjust my ISC motor and Throttle Positioning Sensor. I know the correct output readings I'm supposed to have but I don't have the tools to read the RPM's or voltage output. It shouldn't take long b/c everything is already installed, just not adjusted correctly and it's setting the service enginge light on.