Surging idle. Fix?
 

Before you move this to the PFC forum, please know that I have read every thread in there and tried every method of fixing to no avail.. I figure there might be more response in the 3rd gen forum, although this IS PFC related I believe.

Car: 93 FD

Motor: Lg streetport 13BREW

Turbo: TO4R

Fuel: 850/1680 SX reg, dual walboros @ 12V

ECU: PFC/Commander

Full exhaust, fmic... etc

I have done the learn mode 3 times. I have unplugged the Idle motor from the back of the UIM. I have loaded Chuck Westbrooks fuel maps and relearned the idle.

I've done it all SEVERAL times. No luck. I can't get the goddamn surge to go away.. Ive adjusted the air bleed, the idle screw, and tried a new TPS..

Does ANYONE have any other ideas? I've been fighting this thing for 2 weeks. I must be missing something, but I don't know where to look.

It is my understanding that tuning for the streetport has to be done, but I was under the impression that the maps I loaded (manually I might add) would cure the problem.

I'm on the verge of offering $$ for a fix action, so if you have ideas let me have the.. A running car is worth it to me.

Thanks for the time.

Justin

It would help if you can discribe how the idle is surging. Is it dropping low to the point of almost dying, is it going high, a better discription would help.

Surging Idle
 

The following worked for me.

1- Turn the air bleed screw under the elbow all the way in (clockwise) and then back out 1/4 turn.

2- Back out the idle speed adjust screw on the front of the throttle body till it no longer touches. I backed it out untill i saw clearance under the screw, turned it in by hand until I could feel it touch, and then backed out a half a turn. When you tighten the nut to lock it down this adjustment may change. The end result is that you do not want this adjustment doing anything.

3- In the PFC commander set the fuel in cells N1-N4 to P01-P05 as follows. This will smooth the loopy idle.

N1 N2 N3 N4 N5

P01 105 105 100 100 105

P02 105 105 100 100 105

P03 100 100 100 100 105

P04 100 100 100 100 105

P05 105 100 100 100 100


Let me know how you make out. I assume you have the Idle Control Valve still hooked up.

It's just surging between 700 and 1500.. Up down up down... Won't stop..

Re: Surging Idle
 

I'll give that a shot. Thanks!

throttle position sensor, isc?

Unplugged the ISC (As advised) and tried a new TPS, and several different adjustments.. Nothing worked. :(

o sorry, i guess i missed it..

hmm, i'll go with what mklinger stated..

Was the ISC connected when you did the idle learn ?

Do you still have the fuel pressure regulator. This dramatically improved my idle. Also is this when cold or after hot. Because when its cold I have a hard time starting up and get some surge but as it gets hot, it settles down.

After you unplug the Idle Control your idle will not adjust to either ELD or AC loads. The additional load on the engine will cause the idle to decrease as there is no compensation via the ISC. However, this might work if you set the idle high enough, like 900-1000 RPM.

BTW..my idle is rock steady at 750, with the adjustments described above. Also, the behavior is such that the engine speed drops to about 1100 for about 15 seconds before then dropping to 750. At either speed the idle is constant with no hunting or surging. My Idle Control is plugged in.

I am convinced that the issue is to much air. Driving the air bleed screw almost all the way in and shutting the throttle plates as far as they go, certainly reduces this condition. Before I made these adjustments my idle was all over the board as you described, 800-1500.

could be a vacum leak. thats what mine was. it was on the LIM

Ive done the steps both with it plugged in and unplugged... Neither works.

Nope. Stock FPR is gone. SX regulator is in place. Solenoid is also gone.

Checked. I didn't find any, although with the surging idle it's really hard to tell... I might check that again.. That was my first thought as well...

Thanks for the info. I have driven the screw all the way in.. The surging went down significantly, however did not stop..

Are you sure your IAC is working? I had to take mine out and soak the valve deal in brake cleaner.

Yeah.. It works. :)

What happens when you turn the IGN and O2 idle control off? Assuming you have a Datalogit too?