I have a strange problem with my idle, I am suspecting something with the PFC and the stock air temp gauge but am just guessing.

After my car warms up to about 180F, if it is higher than 65F outside my idle will be erratic, dropping rpms and vacuum. If it is cooler say 50F it never happens... Any ideas?

Thanks

 

Did it just start happening?

I had a similar problem right after installing the PFC + doing the self idle learn, cold start would never be a problem, a warm start would cause it to hunt.

I fixed it by adjusting the idle screw, I did the suggested 1/2 turn out from full close and had the mentioned problem. So I went for 1/4 turn from full close and the problem is gone.

 

has the PFC been tuned at all?

 

The car doesn't have to be started hot for this to happen, I can just pull up to a light and it will start. I've tried to have it re-learn and this always pops up. I can try a 1/4 turn and see if that helps. Also the PFC has not been tuned, it is the base "mod" map. Version B maybe, been awhile since I looked.

 

funny, mine does something similar, has to fully warm up for the idle to jump around.
I'm just too lazy to do anything about it right now, it pulls vacuum normally, I'm just gonna reset the aas to a 1/4 turn and see what happens, might do it tonight if it breaks 50 degrees outside.

 

With the 1/4 out, the theory I read somewhere was the PFC cannot hold the idle down at 720rpm or at low rpm with the screw 1/2 out.

If you like an low idle like 720 rpm, then the screw 1/4 out did the trick for me. I have also read others have fixed this issue by increasing the idle rpm to 1000rpm in the PFC (can be done with hand controller).

Either way, the same goal is reached. No warm start idle hunting

 

I already have the RPMs up a little higher hoping that would help but no go. Turning on the AC fixes it briefly but then it will start again and turning it off will fix it briefly as well, I am talking seconds though. Afraid I haven't tried the 1/4 turn yet due to not driving it, weather sucks here at the moment.

 

clutch switch ok?

 

Here are some other things to try from other threads that I collected before I found my fix.

I really hope its the idle screw 1/4 out for your sake because thats the easiest of the lot IMO.

Good luck!


TPS Adjustment:
http://www.fd3s.net/tps_adjustment.html


Adjust fuel map and IAT correction table
Think a datalogit maybe required.


PFC Idle Re-Learn
Basically start again! Initialise PFC, or disconnect battery. Have idle screw 1/4 rotation out from closed and do the PFC relearn process.


Adjust Cold Start Temp Compensation
Increase the cold start temp compensation on the PFC at the 70C bracket gradually until the idle smooths out during this transition period.


Disable 02 Feedback
Turn off the 02 F/B. If it works, you can leave it off, but make sure your tuner has done a good job on tuning the car at light throttle or fuel economy is going to suffer. No idea what other repercussions there will be in doing this other than the fuel economy...


Warm Up AFR Tuning
https://www.rx7club.com/showpost.php?...5&postcount=20



Theories:

-The 02 feedback, if switched on, comes into play once the engine temp reaches 70C on the GTR and this is when it starts the hunting. The temp for the FD may be slightly different at which this occurs. During the 70c to 90c period the engine head is still coming up to operating temp during which time the engine would still be sensitive to a lean AFR of 14.7:1 and cause the hunting idle. Once over 90C the fuel is atomising properly, instead of partially condensing on the back of the valve head and the idle will smooth out.


-Faulty 02 sensor


-Faulty IACV or out of spec

 

Yeah, clutch doesn't seem to do anything, in fact I replaced the switch even though it checked out but didn't help.

As to the other reply the TPS is within all specs, plus it was replaced about 2 years ago...
O2 sensor has been disabled since I installed the PFC.

I'll need to look into the tuning threads. Thanks for the links.

 

I need to add stuff about dashpot adjustment and fuel cut setting adjustment to my big thread on PFC setup, I just haven't gotten around to it. They do play a big role in idle stability on deceleration.