alright i see alot of idle issues on here already but here is mine:
1993 rx7, single turbo, emissions deleted, several upgrades.

i got the car march 1st. it typically idles at 1100, a/f is 11.5 , its a freash rebuild so i figured i'd just keep it like this for a while until broken in, then i can get the tuner to re-tune it and fix the rich idle.


a few days ago, i went to use the ac, since the previous owner said it works.

i used the ac for about 5 min. then turned it off.
after coming to a stop, the idle was now at 1300 and the a/f was jumping from 10.9 to 11.5

the way it sounded reminds me of cruising on a highway. taking your foot off throttle but then placing your foot ever so slightly on the throttle, you get that babababab noise. its not horrific, but its enough awkwardness on idle to make me want to fix it ASAP.


i drove about an hour running around town with it acting this way. stomping on the breaks 4-5 times fast, in a row raises the idle like it should. about 1400-1500, but then it doesnt go back down to the previously set 1100, just 1300 with odd sound.

75% of all my stops the other day were 1300 idle. 25% of the time it WOULD go back to normal, 1100


BACV has been deleted.

i believe the ecu is stuck in idle lifter mode? and the idle lifter mode isnt tuned correctly.

now what.

 

The FD has a Idle Speed Control Solenoid but it is the same thing.
If it is disabled then those 3 idle speeds do noting as you now have a pure manual
idle air control system. You can set the 3 fuel cut speeds to 1600-2000 rpm so the engine gets fuel sooner when letting off the throttle. This helps recover.

You might as well set all three idle speeds to 0 with the DL to be able to go to being able to also control idle timing.

 

thank you for the quick response.

the a/c button is off, the *** is turned to off (unless the logicon unit is saying its on still) but my idle is 75% of the time higher.


with what i said in my OP, do you believe that, going into the DL and adjusting the settings you stated above, may be able to fix my issue? do you have any other ideas that could contribute to my idle issue, other then vac leak.


again, thank you! i will read up on setting up those settings in the PFC.

 

A stock FD with fully functioning idle and AC, after installing a PFC; will not have the AC properly functioning on all 4 fan speeds. There are fixes posted for this.

Then if you remove the air pump, you need to turn of the O2 idle control system.

Then if you remove the air control valve on the UIM, this tends to mess up the 3 idle speeds so they no longer work.

Remove the ISC solenoid, and you have three co dependent idle speeds that vary due to engine loading.

During all of this with the stock timing control that the PFC uses, you now have a more unstable idle.


Contact arghx to join the best PFC/DL tuning group that has notes on all of this and more.

 

thank you i will look into all of that. (i understand all of it, thank you very much that makes sense)

but let me double check this one thing thats bothering me.

my ac is OFF , and now im having idle issues. im not trying to run the ac any more, and my idle is messed up after the first attempt at using the ac.

thats the issue.

if the idle was messed up only while using the ac. thats one thing. but after using the ac for the first time, now the idle is all messed up.

THATS my problem.

i'll be doing what you said above. thank you!

 

With my 100% manual idle control, initially idle would be set with A/C working, driving lights on,
and the cooling fans running. Depends on porting for your rpm set. Mine was 950. Thus with no load the rpms were about 1200.

These two points in the maps were far enough separated to be timing and fuel tuned independently.

Then I made my own ISC type valve that works only for the AC.
This keeps the idle around 950-1000 under all conditions.

 

so.. guess what it was?








battery terminal, neg terminal was loose. i went threw everything last night , inspecting and trying to figure out the issue. went to start it and i had no cranking amps. went to jump start and found that the neg terminal was loose ( i attach neg jumper clamp to strut tower )

i replaced the terminal and the idle is more consistent, it starts up quicker, and no more funny idle. it still idles rich. and i lowered the idle from 1100 to 1000 with the idle stop screw.