Ive been having idle problems with my PFC for a while

Car is an auto with the Banzai Racing Harness

I noticed that on the commander it always has electrical load illuminated.

The 4 pins have been removed from the PFC (Its an SR Motorsports PFC), and I clipped the egr wire that runs to the stock ecu anyway (car runds stock ecu as well to control the transmission computer). The other three wires going to the stock ecu are deleted on the banzai harness.

The car hunted for idle continuously until the IAC was unplugged. Idle speed still varies a lot but at least it doesn't hunt anymore. This kind of sucks because I want to use power steering and A/C and not habe the car bog down.

What else would cause screwy idle and why is electircal load always illuminated with nothing turned on?

 

Wonder if it senses the other ecu as a load.

 

I suppose I could unplug the stock ecu and see...

I do know that it doesn't run any better with it unplugged though. I tried it as part of my idle troubleshooting routine.

I just noticed the electrical load illuminated last night though and wondered if this could explain part of my erratic idle.

 

There are only a couple things that feed the EL control unit see page Z-30 B-1b

Combo switch (lights)
Heater switch (fans)
CPU no.1 (defrost)

Have you tried unplugging the EL unit?

 

For some reason I cannot duplicate what happened after unplugging the harness and plugging it back in. Maybe the fans were on low and I couldn't hear them or I hit the defrost button instead of the fog lights.

Banzai -

Since you checked in - am I correct to have cut the egr wire that leads to the STOCK ECU? It seemed to help my idle but plugging in the IAC opens up a whole new can of worms.

 

You just need to cut the four wires going to the PFC outlined in the PFC instructions. We keep those four wires intact on the adapter just in case someone wants to use something different than the PFC. Wire 3J going to the stock ECU can be left alone.

Plug the ISC back in and adjust the screw on the bottom of the TB.

 

^^^Pins don't exist on the PFC. Do I have to reattach the egr wire I cut to the stock ECU or can it be left cut? Curiously, The car would not even TRY to stop hunting until I cut this wire- the car would just hunt and hunt and hunt and hunt. After I cut the EGR wire to the stock ECU it idled for a minute! Of course it still hunted at the most inopportune and embarassing times.

I've adjusted that screw (and adjusted and adjusted). When I got pissed from all that adjusting I adjusted it some more.

Then I had a friend adjust it for a while.

This car flat out refuses to idle until the IAC is unplugged. It sucks not having the IAC plugged in with AC and power steering.

Is it possible I have a bad IAC? (maybe needs cleaned or replaced?) This is what I'm thinking at this point.

 

Since the stock ecu has absolutely nothing to do with engine control any longer cutting the wire didn't really do anything.

The air bleed screw on the bottom does not always get the job done, you may need to adjust the other two set screws on the TB.

 

Cutting the wire made me feel better. Gasoline and a match was next.

I know about the coarse adjustment on the front of the TB and the PITA one under the elbow... where and what does the third one do?

 

Top/ front horizontal screw sets the gap of the secondary throttle plates, you may need to close these a bit and open the bottom screw to stop the pulsing. Remember to always verify your TPS values are still within spec when you change TB settings. Check them on the commander VTA1 & VTA2

 

Without starting the car and cold:

VTA1: .61V
VTA2: 1.41V

 

The cold TPS voltages are not the base values. They are normally higher due to the hot wax rod/ fast idle cam opening the throttle for cold starting.

 

Chuck - I started the car and let it warm up.

At 90 degrees C water temp on PFC Commander:

VTA1: .61V
VTA2: 1.38V

As the car warms up, the idle increases from 900 RPM cold to about 1300 RPM warm. I can tell it wants to hunt and hunt for idle if I blip the throttle but with the IAC unplugged it doesn't hunt more than one or two times.

Banzai-

I have to set the idle a little high from the coarse adjustment on the front of the TB because otherwise the car falls flat on its face when I put it in Drive. I think if the car idled about 900 ish RPM all the time in Neutral or Park it would be perfect. Putting the car in Drive would drop the idle to about 750 or 800? What was your target idle speed on your test cars?

 

Looks like your thermal wax is not working properly, this is keeping your throttle plates open and causing the idle issue. This is not something that is controlled by the PFC. ON the back side of teh TB is a cylinder with a "button" sticking out of the bottom, there is a screw with a spring resting against it. For the sake of testing stick something between them (matchbook or whatever) this will close the throttle linkage.

The thermal wax is supposed to expand as the car warms up. This closes the throttle plates and lowers the idle as it gets closer to operating temperature.

Your TPS values should drop as the car warms also.

 

^^^ I effectively disabled the fast idle cam but putting a piece of rubber between the thermal wax and cam. I do not think it is operational and I will disable or replace it later.
This is what the TPS sensors read which is within spec in the FSM:
VTA1: .37 V
VTA2: .83V

 

Anyhoo,

I plugged the ISC back in. It was a bad idea to unplug it in the first place. Turns out not only does it keep the AC happy, it also keeps the car from backfiring on deceleration to an extent. Ive learned a lot about the car today at the very least.

No amount of adjustment on the idle adjustment screw or air bleed screw will stop the car from hunting.

So, what does the control screw in the picture below control? What would it be called in the FSM?




Yes I know my idle main idle control screw looks like ****. Anyone have a spare they could toss in an envelope and mail it to me?

 

Top/ front horizontal screw sets the gap of the secondary throttle plates, you may need to close these a bit and open the bottom screw to stop the pulsing. Remember to always verify your TPS values are still within spec when you change TB settings. Check them on the commander VTA1 & VTA2

The TPS values you have listed now are too low. I can see in the pic of the spacer that the thermal wax has fully extended the button and that someone has tried adjusting the screw all the way in. You might want to get this to someone that knows how to set up a TB correctly, this is not something that is easy to do, and if you do not know what you are doing you can very easily make it worse.

 

^^^

Okay, fast idle is disengaged. I will likely replace the mechanism. That button doesn't move. Its stuck where it is.

Close the secondary plates a bit.

Open the primary plates a bit. This should also raise the TPS voltages. The ones I posted are in spec at closed throttle with the fast idle disengaged. If they are too low, where should they be?

 

They are not "out of spec" low , I just set them closer to the upper limit to avaoid any throttle tip-in issues. For right now just leave the TPS where it is until you get the rest of the set screws dialed in.

 

^^^ Turns out the secondary throttle plates were already closed and no more adjustment that way. Still hunts and hunts and drives me insane. Only pulling the ISC plug gives any relief.

I removed the ISC and tested it per the FSM. Just because.

Seems to be in spec once it cools down (FSM says to test at 68F).

So here I am.

Car in pieces again. Pissed.

 

This may be a completely useless perspective but...

have you tried using the air adjust screw to adjust the idle to a stable 800ish (or whatever the target is) with the ISC disconnected and all 3 idles set to 0 in the datalogit.

Then go into your datalogit, reset the PFC, set the idle speeds properly, then start the car to redo the idle relearn procedure? The idea is to get the car to idle on its own without the help of the ISC, and then the ISC only kicks in to reduce backfiring on decel and idle up when under load. That's how you usually set the idle on other EMS's with a duty cycle controlled ISC valve (not a stepper motor like say on a Mitsu engine).

I'm guessing the PFC has to determine a baseline level of ISC duty cycle based on the amount of air flowing through the TB, air that is determined by the adjustment of those screws. On a Honda (using a Hondata s300 reprogrammable ECU which is speed density and a lot like the PFC in terms of features) I have had the idle hunting problem you describe.

On that car you usually leave the throttle plate adjuster screw alone and you adjust the air adjust screw with the ISC disconnected to idle stably at a specific rpm. On that car, it's 500ish with the ISC disconnected. Then you reconnect the ISC and adjust ISC duty cycle (it has a crude slider bar for adjustment) so that it neither hunts at idle, nor stalls on decel, nor sticks at a high rpm on decel.

On that particular Civic there was insufficient idle air coming through without the ISC. So I had to have ISC duty cycle pretty high to keep it alive, which resulted in some hunting. So I added a little idle air, reduced ISC duty cycle, and it stabilized. The problem is that the PFC does not let you directly monitor or control ISC duty cycle, only do this phantom idle learn procedure which nobody really understands. We do not know exactly what amount of range of baseline idle air (by baseline I mean the amount of air determined by those adjuster screws) the PFC expects for its duty cycle calculations, and that's one of the reasons why it's such a pain in the *** to get it set up right. If the PFC works anything like that Hondata, the ISC duty cycle is too high and the idle is hunting--kinda like an EBC with the gain too high. We just need to figure out how to get the duty cycle down by:

1. through some guesswork, ascertain what the operating range of idle air should be (without the ISC). We can fiddle with the TB screws and try different things, that's about the only option here.
2. somehow get the PFC to use an appropriate gain/duty cycle setting for whatever that appropriate level of idle air may be. The PFC adjusts ISC duty cycle in some way during the idle learn procedure, we just have no idea how it does so. This is one of the things that really frustrates me about the PFC. On a Hondata or Haltech you have more adjustabililty.

If I had the car in my possession right now, here is what I would do as a sort of experiment:

1. Using mostly the air adjust screw if possible, get the car to idle with manual idle control (idles set to 0, ISC disconnected) at 800rpm, then perform idle relearn with idles set properly in the Datalogit. Observe results. IF idle still hunts:

2. get the car to idle with manual idle control (idles set to 0, ISC disconnected) at ~700rpm, then perform idle relearn. Observe results. IF idle still hunts:

3. get the car to idle with manual idle control (idles set to 0, ISC disconnected) at ~600rpm, then perform idle relearn. Observe results. Continue that process trying different "base" idle speeds, while making sure the ELD computer and TPS and all other external factors are all working properly. The idea is to "hone in" on whatever mysterious level of idle air the PFC can operate within after doing its idle relearn. You would also have to be careful not to mess with fuel and timing too much as that would affect the experiment. The key once again is to set a "base idle" without the ISC. Then the PFC will hopefully learn a duty cycle range that results in a stable idle speed with the ISC connected and working.

I don't know if that made any sense to anyone but I hope it helps in some way.

 

You may only need to add/subtract fuel from the idle cells on the PFC... the base map on the PFC is not all that great, and every car pulls different vacuum at idle. The base map that comes preloaded is only a starting point. If your car pulls better vacuum than other cars then you may be into the 1.215 cells of the default map.

 

BTW, the secondary throttle plates need to be open a little, so the fact that you have them completely closed can also cause the surging.

 

Chuck Westbrook - can I make an appointment?

I want this auto running on the PFC for SevenStock!

 

I replaced my ISC with a known good one. No dice.

I am going to remove my AWS when the block off plates arrive. The AWS still revs the car to 3000 at start up even though the poins are removed on the PFC. I have a down pipe so no need for this. Should eliminate one more thing that could be wrong.

I noticed that the PAC (Port Air Control) illuminates on the commander in time with my hunting idle. How could this be related?