milano maroon

iTrader: (1)

I have been working with my idle, trying to get it stabilized and seem to have a problem with stalling. Here's what is happening. Will start to back down the driveway, am going pretty slow, will put the clutch in and coast for a little bit, put the brake on and the idle will drop to 500 or 600 rpm, stay there a little bit, and if I'm lucky will go back up to 1050 or so. Sometimes it doesn't recover and stalls. Will do this just about every time. Clutch in, slow coast, brake on, and idle drops, then picks up...usually. Goes through cells N3/P7, N2/P7, and to N1/P8.

So here's what I have done - set fuel to about 13.5 AFR in those cells, tried advancing timing (but may not have an effect if PFC is controlling timing).

Running PFC controlled idle, ISC installed, clutch switch works (sends a signal to the PFC Sensor check screen), F/C is 1180, Idle is 1080 (if I raise F/C too much I get a surging idle). I have adjusted the dashpot as best I could but I really need a new one, the plunger doesn't stick out very far. But I don't think it's a dashpot issue - I can coast for a little while with throttle off, clutch in, but it seems like when I put the brake on I get the drop in idle.

One thing I noticed tonight - it will do it when running No load idle and E Load, but when I turned on A/C Load it didn't want to drop.

I have attached a log showing the idle drop and a stall. A lot of times though it will recover but it seems to be on the ragged edge.

Any ideas?

Thanks for any help you can give me.

Banzai-Racing

iTrader: (11)

Check the clutch switch on the pedal assembly.

milano maroon

iTrader: (1)

Thank you for the reply. The clutch switch dot on the Commander Etc. Sensor Check screen lights up and goes off as I depress and let up the clutch. Could I have it backwards somehow? Car was an auto to M/T swap and didn't have this hooked up when I bought it (hooked switch to 1Q on ECU). Can't really see though how to reverse this.

Screen shows -

clutch out - dot is not lit
clutch in - dot turns black

Could someone check their sensor screen and tell me if that is correct?

My next step will be to unplug switch and see if that changes anything.

arghx

iTrader: (3)

you need that dashpot working man. I've found it to be very helpful in solving those low speed stalling issues, which can happen with a lightweight flywheel. Either the dashpot is bad or something is out of adjustment.

milano maroon

iTrader: (1)

Thanks for the replies and help. Unfortunately it's not the dashpot. While my dashpot wasn't working I put one on that was. It did help in instances where I backed off of the throttle but not in this instance.

Have tried adjusting fuel cut, idle speed, air bleed and even the idle air screw but it still stalls from time to time.

Here's the scenario - slowing down to a stop sign, put the brake on and rpms drop to maybe 600 rpm or so. Sometimes it recovers, sometimes it doesn't. If I don't put the brake on, it won't stall.

Clutch switch works.

Brake switch works.

Both show up on the Commander if I push them.

Any ideas?

cewrx7r1

iTrader: (2)

Will start to back down the driveway, am going pretty slow, will put the clutch in and coast for a little bit, put the brake on and the idle will drop to 500 or 600 rpm, stay there a little bit, and if I'm lucky will go back up to 1050 or so. Sometimes it doesn't recover and stalls.
It means that FC is set too low or air adjusting screw needs fine tuning.


F/C is 1180, Idle is 1080 (if I raise F/C too much I get a surging idle).
FC should be at lease 200 rpm over fuel cut. Surging mean it has too much or too litlle ide air

Verify correct TPS voltages, adjust fuel for best hot idle, then lastly adjust air for good recovery.

It also might be an air pump/O2 sensor/O2FB combination problem.

BoostCrzy

have you tried giving a little more fuel in these cells?...

milano maroon

iTrader: (1)

Thanks for the replies. I'll keep adjusting.

Am running an ISC. Not running an airpump and O2 feedback is off.

I am going to investigate the TPS also. It is adjusted within spec. but on the low side. Whenever I try to adjust on the higher side (VTA1 around 1.25 and VTA2 near .7) the idle will not slow down below 2k. Could be just something I'm doing wrong.

Jeff

arghx

iTrader: (3)

You can try raising both target idle speed and F/C speed by 100 rpm.

milano maroon

iTrader: (1)

So I wanted to update this thread in case anyone else experiences this problem this may help.

I had originally set up my idle adjustment screw on the paint marks with maybe only 1 or 2 revolutions (can't remember) of pressure on the butterfly. Engine hot, no fast idle interference. And only 1/2 to 3/4 revolution of opening on the throttle adjust screw (under the elbow). Went through the idle learn process and was pretty good except for the stalling issue at stop signs etc. I need to mention here, this is an HBP engine, I have been told idle air requirements can differ a little from a street port.

So I ended up slowly opening the idle adjustment screw, a little at a time, maybe an 1/8 revolution. Did this over the course of several days/weeks. Never raised the idle by screwing too much. I am assuming the PFC was compensating for these minor adjustments by closing down the ISC.

Anyway, I am probably about 2 revolutions tighter (more air through the throttle plates) than when I first started. Stalling at stop signs has decreased a lot, rarely does it now. May continue tweaking the air a little more.

Only negative is I could not get the 200 rpms between idle speeds and fuel cuts like Chuck suggested. When I go over 100 or 120 difference I get surging. As soon as I cut it back the surging stops and idles very solidly.

Anyway, I just wanted to add my solution in case anyone else ever has this problem. Thanks to everyone who helped with this.

arghx

iTrader: (3)

What are your ISC valve duty cycles at idle now? It is "Advance ???(2)" where 0 = 0% duty and 1000 = 100% duty . I wish I could see the before and after. I bet they were nearly maxed out even under no-load idle.

milano maroon

iTrader: (1)

I'll run a log in the next few days and see if I can find one from a little while back to compare. I'm glad you asked because I have been having trouble interpreting the ISC on my older logs. It seems as if the no load duty would be running around 900 or so and when I turned on the E Load or A/C Load the duty actually decreased. Definitely a change in duty but I was expecting it to go the other direction. Big differences in timing advances though when adding loads.

arghx

iTrader: (3)

I have come to the conclusion that as idle loads increase (A/C and E/L) it is the ignition timing that is mostly used to raise idle speed. The ISC valve has a bigger role in the electronic dashpot function--that's part of the reason duty cycle increases as rpms go up--to help "catch" the idle when you let off the gas. I thought the Rx-7 PFC was unique in this behavior until I started datalogging a Nissan SR20 D jetro (speed density) PFC. I've also been reading about the ISC valve on the Evos (which is a stepper type) and they ramp up the ISC steps (open the valve further) as rpms go up. See this thread:

http://forums.evolutionm.net/ecuflas...sassembly.html it's about disassembling the Evo VIII ECU to locate the control tables for their ISC valve

Getting back to the PFC... if you want to see something interesting, perform an idle learning procedure on a warm engine while logging Advance. Warm the engine up. Save the map. Reset the PFC (key on/key off) and load the map in there before starting the engine. Look at ISC duty, leading and trailing ignition timing, rpm, and PIM as you log. Then you'll see exactly what the PFC is actually doing when it's "learning" the idle and how that in turn affects the vacuum signal and rpm. Make sure you go through the whole procedure (no load, E/L, A/C)