idle problem
 

please help!!!
idling up and down around 1500rpm, already changed spark plugs; checked vaccum by spraying the engine bay with rough idle, no signs; checked the IACV by jumping it with 12 v, "clicks", so that works; i am goin to clean the throttle; besides taht, what else should i check?

set the throttle position sensor

Make sure your TPS is in spec and adjusted properly. Get one of these http://www.boostpro.net/prodtester.html to test for intake leaks, it's MANY times easier and more effective.

Give us more info on the car. Turbo? Modifications? Et cetera.

http://www.johnr.com/tps.html

instruction above the link, is that how to adjust the TPS?

some say unplug the TPS and BAC while idling rough, if idle back to "normal"(rmp not jumping i guess), then either the TPS or BAC goes bad?

i dont have much machanic skill, but i will read thru any helpful instruction detail to make this work.

anyone have the same idle problem and ahve it solved?

http://www.fc3spro.com/TECH/HOWTO/TPS/tps.html
The link you put up is correct. I prefer the voltmeter writeup includes pictures. Another sign of an out of adjustment tps is that the car will buck under very light or no throttle when cruising.
If you want to check the BAC valve, unplug it while the engine is idling and see if the clicking noise stops. I think it's the tps though.

oh, i have a 86 GXL N/A stock 82,000 miles, recently changed spark plugs, teh previous owner had leading plugs placed at trailing spots and trailing plugs placed at leading. but idling problem occured before new plugs was replaced.
so the link for set the TPS works on N/A as well?

Same for NA. Even easier because there won't be an intercooler in the way.

my reading shows 0, whats that mean? i unplug teh tps, stick the red pin to green and yellow wire, black pin to red and black wire, is my tps done?
the car idle 2000 rpm stable after i unplug the tps.

Are you sure about the color combination? Are you checking the resistance (ohms)? There is a screw (surrounded by spring) near the TPS used to set it to spec. In your case 1 ohm.

i tried all three wires, checked with current. only saw "0" on the display. too bad it's snowing all weekend, i am not able to check it, if comes a better weather, i am going to shoot couple pics and hopefully i can post on this thread.

i just took out the intake tubing, wipe of some dust at the throttle body near the plates area, but i didnt take the whole throttle body out, stilll attach with the engine.

i checked the tps resistant, it shows 1.197k ohm at cold.

then i started the car, push the tps tip all the way down, idle drop to around 1k from 2.5k, maybe lower than 1k, i didnt see teh rpm gage, but sounds kinda low, then it rev up and down at low rpm.

the idle still rev up and down at 1500 after it warms up; idle stays 2k after i unplug the tps wire plug.

but then i push the tps tip all the way down again while it revs up and down at 1.5k, no sign of change.

should i change teh tps? or go ahead check somethign else? like temp sensor for coolant?

I still think it is the throttle position sensor. After letting the engine get to operating temp, unplug and check the tps resistance (ohm's) again. I think you have the right wires green and black. Adjust to 1k ohm at the idle position. If you press the plunger all the way in, the resistance should change to 4~6 k ohm. The sensor is kinda expensive so you can check it with the specs in the factory service manual available online.

looks like it is tps problem, it shows 1230kohn at idle, 384 ohm when i press the tps tip allrhe way down. i have done that with warmed up engine, so i am gonna go ahead purchase a tps from ebay9hope they work), see wats happening next.

So, if it reads 1230 at idle, why don't you adjust it to read 1K?

Can you adjust it to ouput one volt dc at idle with a hot engine? Have you tried to do that?

When the throttle is held wide open, what is the voltage reading in dc volts?

And you know the 86FSM says to NOT hold the plunger all the way in for extended periods of time? There is a check for holding the plunger in, but it's a momentary thing.

FSM says to hold the rpm at two grand and move the plunger in and when you do the engine speed should vary, but to NOT hold the plunger in completely.

The TPS is set with a hot engine. You use the two LED light method mentioned in the FSM and the result after doing so, is.......................an output from the TPS to the ECU of approx 1vdc (See CONTROL UNIT page and the reading of pin 2G at idle).

Given that...........if the engine is HOT and you backprobe the green/red wire on the harness side of the TPS connector, and it reads approx 1vdc at idle, then the TPS is set right. IF it does not read approx 1vdc, then adjust the TPS screw til the meter reads 1vdc output of the TPS to the ECU.

Moving the TPS plunger in/out does not directly change the fuel amount from the injectors. It moves the output value of the TPS to the ECU from one value to another. The change of value puts makes the ECU think it's in another ZONE of operation, therefore the rpm changes some. See Training Manual somewhere on this site or the web somewhere.

I explained to him in detail how to do that but who knows if he tried.