Idle Surge Throttle body or sensors on it not causing it

[xman]

Ok I have read a lot of the forums but I can not find anything on Idol surge when car is moving but not at idol and the problem not having any thing to do with the throttle body or sensors on it. I have taken a throttle body with all the sensors on it from a good running car and put it on the car with the idol surge problem and the surge is still there.
This trouble I am having is on a 1991 non turbo 2.0 FWD Eclipse 5 speed

I am lining toward the Seed sensor or motion sensor? is this sensor located in the interment panel attached to the speedometer on 1G?

Any ideas on how to take care of this would be great.

Thanks

 

[donmagicjuan]

First of all, "idle surge while the car is moving but not at idle" is a bit of an oxymoron, which is probably why you didn't find anything on it in a search. Have you checked the capacitors in the ECU? A leaky capacitor can cause a number of driveability issues, and with your car as old as it is, it'd be the next thing I checked after the components related to the throttle body.

 

[xman]

I did my search in the forums for idle surge.
The ECU that is in the car at this time has been repaired by Steve Piette so I do not think the ECU is the problem and I have 3 ECU's that I have tried in this car and I still have the idle surge problem.
Thanks for trying to help

 

[RSTurboFWD90]

After reading your post I am not understanding your idle problem. Usually, idle surge means the engine rpm is not steady at 750 rpm when your throttle body is closed. Sometimes the idle will be 300 rpm and then jump to 2000 rpm and then back to 300 rpm and perhaps even stall the engine. Your car can be moving but your throttle body must be closed for it to be called idle surge. There are quit a few knowledgable members here that can help. Please give a bit more detail on how your car behaves. I'm sure someone will give some good advice.

 

[donmagicjuan]

If I am interpreting it correctly, I now understand the problem to be "idle surge while the car is coasting, but no surge while the car is stopped." Unfortunately, I don't know the location of the 1G VSS, as it's different from the 2Gs. I believe everything comes off of the cable for the speedometer, though.

 

[xman]

This car when setting and idling runs fine it has an idle speed of about 800 rpm's, but when you are driving the car and push the clutch in and are costing down the road the rpm's surge from about 1100 to 1500 rpm's and it dose this no matter how little you are moving ¼ mph to 80 mph when the car moves the rpm's surge when the car stops the surge stops.
It is not the throttle body or any of the sensors on the throttle body, it is not the ECU, it is not the MAS, and it is not the oxygen sensor, there is no intake leaks that I can find. I have swapped just about every part I can think of from a good running downer car but the surge in still there.
I think the speed sensor is what may be causing this but I am not sheer were it is at on this 1g car so I can not swap it from the downer car till I find out? But it may be something that I have not tried so any suggestion on what may help is greatly appreciated.

 

[steve]

The speed sensor on a 1G is inside the speedometer. It's a magnetic reed switch.
You can check that it's working by using the cruise control or looking for the output on the DLC.

Steve

 

[xman]

The speed sensor doses not appear to be the problem either because I put the dash panel from my good running downer car and I still had the idle surge. I found out that if I unplug the idle stop sensor that the idle surge goes away. What would be the down side to leaving the idle stop sensor unplugged and not to use it any more, I turned the idle speed up and the car seams to run good and dose not appear to affect the drivability any.
Thanks

 

[91turbotalon]

have you done a boost leak test?It could leak after you start driving because of the load on the car.

 

[xman]

This is not a turbo car, what load are you referring to if it was?
Thanks

 

[RSTurboFWD90]

I know that the idle switch is used to tell the computer you have closed the throttle and it needs to perform certain operations, depending on engine rpm, to keep things tidy. If you eliminate the surging problem by unhooking the idle switch wire then your computer will think your throttle is never closed. You have verified the idle switch is good, right? Then look into other components that will be used when the computer is operating as if the throttle is closed. I know you are going to say you've tried everything else but finding that unhooking the idle switch stops the surge is getting somewhere.

 

[xman]

Yes the idle switch appears to be working fine I believe it is a ground switch that when closed it goes to ground telling the ECU the throttle is shut ? This is the way it is working anyway.

I am not sheer what else the ECU looks at when the throttle is closed? The speed sensor, throttle body sensors, the ECU is rebuilt, the MAS, the oxygen sensor, what is on the car that the ECU looks at when the throttle is closed that I have not looked at?

To all I apologies for my bad spelling and or bad grammar wile on this site I am very sorry for not being better at it, I use Microsoft word to do my spelling and grammar check before posting and it apparently dose not know how to spell any better then me, I apologies once more and I will do my best to do better with spelling on this site.
Thank you