Alright I have a hunting idle when warm.
I have changed the TPS with Two known good working ones that also spec out as per FSM.
I have tried setting them with the Lights, With resistance, and Voltage Running and not. My best results have been with the engine running and backprobing and adjusting to get 1.0v when warm and idling.

Now the car starts and idles arround 1800 rpm and slows as it warms down to a rock solid 800 rpm however after the first time I take the car for a spin I get a hunting idle from 1200-1800 rpm when the car is warm,
I have also cleaned the BAC valve and even cleaned and tried a second one no good.
I have set the idle twice and still no difference.

I am out of ideas, anybody with any?
More details on my escapade here;
https://www.rx7club.com/2nd-generation-specific-1986-1992-17/s5-tps-idle-hunting-hesitation-problems-594021/

 

Did you ground the set coupler and make certain the idle is set around 750/800 with the throttle screw? If the idle is set too high with the throttle screw, the BAC will be working overtime and a hunting idle will be felt.
If this has been done, then we'll go from here.

 

Yes.

 

do you still have your top mount inter cooler? If so try plugging the vacuum line from the intercooler to the manifold. (pasenger side, small hose on the back of the intercooler) it supplies air for the air bypass solenoid. It helps controle idle with a load. If it is sticking open when the computer thinks it is closed you will get a surging idle. (I know from experiance)

 

Only the BAC valve remains. and my top mount has no niples as it is from s4

 

thermo wax pellet

 

how does the thermo wax pellet mean a hunting idle on warm engine? I can see it permanently leaving a high idle... or no help while starting.. etc. But I will check to test the thermowax to see that.

 

Thermowax works as advertised. well at least as per fsm.

 

The thermo wax cold start assist would have nothing to do with a surging idle.

 

Unplug the TPS while it is doing the surging. If it solves it, the TPS is either bad or set incorrectly.

 

Icemark,
Yes it kind of goes away when I unplug the TPS but it runs like **** it sputter and instantly runs Super Rich... I mean REALLY RICH. so I can't really tell if that is the cause or not... but it seems to be irretic, sometimes it surges then I will put the engine under load by applying the e-brake, and then in 1st I will depress the clutch and slowly apply load to the engine then put it in newtral and allow the clutch back up.... it will idle fine again. I don't understand why it would be doing this.

 

I am not sure if it is related but I cannot figure it out either.
The idiot lights, clock, and the Radio flicker on and off but don't really come on... cannot figure out what is going on there. any ideas if it is related?

 

sounds like an electrical problem closely related to fuel or ignition rather than timing. again..it SOUNDS like...still need more info to diagnose..have you removed or tampered with any of the emissions crap? does it smell funny or idle or load? do you have hard time starting, do you have a misfire on decel?

 

bad room fuse... that could also cause the problem with the ECU

 

There are no emissions left.
It runs rich... like it should, not super rich.
Yes I have a hard time starting when cold. But not when warm.
No misfire on decel
There could not be an electrical problem relating my interior problems with that of the idle, other than the alternator and tomorrow I am going to have it tested to find out for sure.

 

I checked it, it looked (visually ok) but I will take it out tomorrow and replace it with a new fuse, see if that fixes my problems.
Keep you posted.

 

Hey, I thought you were supposed to set the TPS when the engine is OFF (after it's warmed up), and with it unplugged from the harness.

Use your MM probes: black probe into black wire, red probe into green wire.

Use the 20k OHM's setting and set to 1k-ohm. Or 1.0

Or maybe you've got all that. If so, see if it does it both in gear and in neutral? Also, do you have a fuel-controller? If no then just ignore the last question.

Either way, 1500-1800 RPM's is the notorious spot for "falling revs" and hunting... I assume it only does it when it's coming out of the warm-up... But how about when you slowly rev the car from 1000 RPM's to 2000?

 

check your alternator voltage.

 

There are a few ways to do it, one is the lights, the other is resistance, the other is voltage. The ecu reads the TPS by voltage so I backprobed for voltage with it not running had it set perfectly, then started the car and it was having problems. Tried it again with the engine running and the setting was off 1/4 of a volt.

Same results as above

Done

Yes does it both gear in and out

No fuel controller

no It ONLY does it when the engine is warm and has been driven.

 

I am having the alternator tested today, and I am going to check the room fuse right now.

 

Ok so interior fuse turned out to be bad! I replaced it with another 7.5 and the radio and all that good stuff worked flawlessly. The idle however is still trying to find itself after going for a spin... however if I am sitting at an intersection and it is hunting if I put it in first hold the brake load the engine under 800 rpm then push the clutch in and back to neutra it holds a strong 800 rpm idle. This is what perplexes me.

 

could be a vacuum leak

 

Try doing the method you said fixes it, and after it's normalized itself--lightly blip the throttle to about 1000-1500 RPM's, then let off.

See if it drops back down to normal or if it trys to "stay" up there at 1500RPM's+ and hunt after the light "blip"... Try blipping the idle with the car both in gear (with the clutch in) and in neutral and see if the results are the same.

 

No it is not a vacume leak, for a relatively new engine 300km's on it, it pulls very good vacume.

The hunting starts anytime the rpm goes above 1200, if the rpms stay always under 1200 the hunting starts again.

I am pretty certain that I have two bad tps's cause both have similar problems but act differently one I cannot get the lights method to work or tune it to 1.0V or 1000 ohms
The other i Can get it tuned in but it hunts, I today used a light check method and cannot get both lights to illuminate so I am pretty sure this one as well is bad... I will have to find another one that is known to be good to try out. Keep you posted.

 

[/QUOTE]... however if I am sitting at an intersection and it is hunting if I put it in first hold the brake load the engine under 800 rpm then push the clutch in and back to neutra it holds a strong 800 rpm idle. This is what perplexes me.[/QUOTE]

I have the same issue, even with a rebuild.
My idle will sometimes fall to 850 RPM where I want it or fall to 1200 RPM, too high.
If I hold the brake and load the engine, it will go down to 800 RPM steady. It drives my crazy.

Checked
Throttle cable
Gas pedal
Cruise cable
TPS
BAC
you name it.

Iv'e noticed that if I apply the clutch above 2000rpm on decel it will fall to 850 but if I apply it lower than 2000 RPM, I get the high idle.

Any insight on this?