K.This problem started just yesterday.I took my car out just to fill up air in the tires and when i got to the gas station before i shut down my car the idle sounded real low like it was gonna stall.well.filled up air got home and I waited in driveway and my idle was fluctuating(sorry for spelling) big time.It would go from about 700rpm or so then sound like it was gonna fall on its face.My idle has never been the best.It did fluctuate before but just a little and it wouldnt get that low.Also before and now my car will idle fine then fluctuate.then i can rev it up a little then it will idle fine then maybe after awhile it might fluctuate again.I dont know exactly when and why it does.Well.Today decided to take a look at my car again.Started her up.idled fine.took her around the block and went back in driveway then vrroooomm....vrrooommm....vrrooooomm.Idle sounded like it was gonna die again.I had my mom rev it up and seemed clean from the exhuast.no smoke.but then once she stopped revving and the idle went back to almost dying i looked at the exhuast and it would go vrrroooomm...(puff of black smoke)...vrrooooomm...(puff of black smoke)...vrroooooom..(puff of black smoke).
My car always smelled like exhuast cuz have no cats or anything but it seemed to smell a little richer. If you guys could help me out.Thanks!!!

 

Throttle return spring? could be weak.

 

vacuum leak(s)?

 

k.im glad its not my engine.cuz my engine does have full power.runs like a beauty when getting on it.

 

12a carb or 13b RE-EGI?

Very important to know this because the troubleshooting of idle issues like this are completely different.

As a point of reference, please provide your car's year, make (G/GS/GSL/GSL-SE), how many miles, what you've done to it, what exhaust you're running, outside air temperature during cold start, amount of tire pressure in the left front tire, number of balance weights on the right rear tire (and position), and the price of gasoline in your hometown.

Will enter these into the Idle Problem Computer and see what spits out...

Seriously, though - more info about the build of your car would help us provide better answers. HTH,

 

sorry.85 GSL so its a 12A.104,000 miles.Mods are header back exhuast 2.5".and racing beat air filter.thats it.oh.and i removed the air pump but still have the rats nest.

 

Some things to think about based on your engine and mods;

Shutter valve - used to block off airflow during deceleration, when this goes out, it can lead to vacuum leaks that result in odd idle conditions. While not easy to change (have to pull carb), it can be the cause of many hard to find problems.

TPS - your carb engine DOES have a Throttle Position Sensor that should be adjusted for idle vs. off-idle conditions (one light). Run a search for the information on how to build the test rig for CARB engines, not the EFI engines.

AP removed - is your Blocking Plate sealed down well? The Blocking Plate that's installed to cover the Air Control Valve that feeds air from the Air Pump to the exhaust needs to be sealed to avoid an intake vacuum and exhaust pressure leak. This could lead to idle issues that you described.

 

I am having EXACTLY the same issue!! My mechanic changed plugs, rotary cap, rottor, fuil filter, air filter and all the usual culprits for poor idle and still I have the problem. Sorry you are having the same problem, but at lesast we have some ideas where to go with it.

Bill

 

Could it be the coolant o-rings for the intake manifold. Check to see if coolant is collecting at the base of the manifold where it meets the engine towards the driver's side.