Djseto

iTrader: (2)

@DaleClark suggested I start a thread to see if the bigger brain trust here can help with a weird idle issue I started experiencing with my car a few weeks ago.

• Engine: 13B Streetport (rebuild by Rotorsports Racing), PowerFC, BW 300-SX-E 8380 Turbo, No AWS system
• More Info: see my build thread: https://www.rx7club.com/build-thread...hread-1127397/
• Problem
  • Will randomly stall when put into the car into neutral. When in gear, there is no problem. Only happens after it’s warmed up.
  • Because it’s not consistent, it’s hard to replicate and test fixes — I basically have to go drive for 20-30 min and try to coast when possible (and safe since it stalls) or find some traffic lights. I’ve tried warming the car up in my driveway and then letting it idle. 9 out of 10 times, it won’t stall.
  • Basically there are Four states of how the car idles:
    • Great. Holds idle in neutral with or without electrical load or A/C on/off. Idle fluctuates within 20-40RPM according to PFC Commander
    • Bouncy. Will sometimes bounce between 1100-1600 RPM. Seems to bounce less with AC on, but when it’s off, it’s all over the place. Managed to capture a video of this:
      You Tube
    • Stall. When I go to neutral, the RPMs drop from whatever I was in gear to 600-700RPM and then just cuts out
    • Almost Stall. Will drop to 600-700PM but then jumps to either Great or Bouncy
• Things Ive tried
  • ISC - I pulled it, sprayed some carb cleaner in, and verified the resistance is good per FSM and also that it opens when 12v is applied
  • Adjusted Air Idle Screw - I’ve played with this a few times but since it rarely stalls sitting in my driveway, it’s hard to really see if this helps or where the screw should really be set
  • Dashpot - pushed on it and it pushes back so I’m pretty sure it’s good
  • Clutch Switch - verified the PFC knows when the clutch is in
  • Throttle position voltage - PFC shows VTA1=.62 and VTA2=1.51
  • Adjusting PFC Idle settings
    • From Rotorports Racing, all F/C Idle settings were set to 1400 RPM, All Idle settings were 1100 RPM
    • A Facebook user suggested I raise the F/C settings to 1700 RPM. I tried it and took it for a short drive, and no stalling, but it wasn’t a long enough drive. Not sure if it really fixed the issue given the randomness
    • Can someone explain to me who the Fuel Cutoff settings actually do? If it’s set to 1400pm, does that mean when I drop below 1400RPM, it cuts the fuel? Don’t I need fuel for the car to not stall. Newbie question for sure
• Things that “changed” since the car was working fine
  • A/C - it wasn’t working and I realized it just needed a charge. I bought a R134 conversion kit (not knowing it was already converted). I put R134 in (oil was pre-mixed in the can of R134) and charged her up to the right amount per the instructions. A/C works good enough.
  • PFC A/C Relay Fix - With A/C on, the PFC sensor wasn’t showing it as being on. I wired in the relay per the posted fix and now the A/C indicator comes on when the compressor is engaged
• Things I have left to check
  • ELD Computer. Haven’t tried any of the FSM steps to troubleshoot if it’s the ELD. As @DaleClark pointed out to me, the ELD light it on in my YouTube Bouncy Idle video. I’m about 99% sure that’s because the radiator fans are running. The fans weren’t working when I dropped my car off with Rotorsports Racing. We decided it was cheaper to get a standalone thermostat from Autozone for like $30 and wire it in than possibly spend hours troubleshooting. I need to see where they tapped power from. In the video when the AC is turned off, there is nothing (lights, stereo, etc) drawing power other than the PFC.

This is driving me nuts. Thankfully she didn’t stall during the Rotary Rally (had a blast!) a few weekends ago. Rotorsports Racing is about a 2 hour drive from me and they are pretty backed up with work. I also want to troubleshoot this myself so I can learn more about my car.

Thanks in advance for the help.

Billy7

iTrader: (7)

I had a similar issue, after the car was fully warmed up, I drove it and at random times, when coming to a stop light, I coast it in neutral and it would just stall on me. It turned out to be a faulty HKS Twin Power (brand new less than a year old) which basically craps out when the car is warm. Perhaps your ignition booster is the first place to start.

Djseto

iTrader: (2)

Hmm. How do you test it? I also have the HKS Twin Ignition Booster. It was on my car when I got it so I have no idea how old it is.

Billy7

iTrader: (7)

Long story short, the last time it stalled, it wouldn't start back up, I was stranded and had to tow it to IRP. Ihor let it idle until it stalled on its own. When they found the culprit, they removed the HKS Twin Power and the car ran with no problems. Of course I upgraded to the SBG IGN-1A afterwards...

DaleClark

iTrader: (55)

The HKS twin power has a harness that just goes between the ignition coil harness and the front main harness. Takes like 2 minutes to unplug it and just plug it in like stock. May be worth doing for troubleshooting but I doubt that's it.

There's also a neutral switch on the transmission, it should show up in the sensor check screen on the commander. When you put it into gear the switch should disengage. Easy thing to check.

Idle can be one of the toughest things to get right. There's a lot of factors that go into setting idle speed and things that can bog down the engine at idle that need to be compensated for.

Also, the PFC is supposed to do an idle learn when you first install it, I'm wondering if it needs to be re-done since you now have working AC. I'm not sure of an easy way to re-start that process or if you need to per se, in my PFC FAQ you typically run the car with no electrical load/no AC for 10 minutes, then electrical load 10 minutes, AC 10 minutes, etc. At first the idle will surge but it will figure it out and smooth out the idle.

The only way I've re-started this process is doing a reset on the PFC. But, if you do that you would lose the map and tuning done by Rotorsports. You would need a Datalogit to back up that map before resetting.

Dale

Djseto

iTrader: (2)

The neutral switch indicator doesn't work. I think it's because the previous owner wired the car to start without having to push the clutch in. I've thought about wiring it back. At the same time, it wasn't an issue before so I wonder why it would be a problem now? I'll try to put that stock ignition back. What risks do I run by using the stock? Will the car be harder to start if it does stall, etc.?

I've read about the PFC re-learn in my research and not being able to get my maps back is the one thing that's held me back. My wife asked me what I want for my birthday and I'm thinking a Datalogit might be it...

AE_Racer

iTrader: (1)

There is 2 switches on the clutch pedal (for usdm). One is for the computer and the other is the starter interlock. I was having trouble with my car dying when coming to a stop and pressing the clutch pedal in. I removed the switch and found the spring very weak. I took one out of a writing pen and it has worked great since.

Djseto

iTrader: (2)

So my issue happens regardless of whether the clutch is pushed in or not. If I'm coasting, I can drop her intro neutral and let off the clutch and she still stalls. I will check the spring though.

AE_Racer

iTrader: (1)

I definitely would look at it. I believe the switch on the PFC is labeled as “CLT”. If its not lighting up, it may not be your whole problem but could help.

Djseto

iTrader: (2)

The CLT light does light up when the clutch pedal is pushed. The Neutral indicator, as I mentioned above though, does not.

AE_Racer

iTrader: (1)

gotcha. I dont think the starter bypass would affect the neutral switch. Typically the two wires for the starter bypass are just joined. The neutral switch is on the transmission.

AE_Racer

iTrader: (1)

Scroll to page 186 of this FSM and you can see the location of the neutral switch. Id just give it a look and make sure its plugged in and check the wiring. http://www.rotaryheads.com/PDF/3rd_g...ol_systems.pdf

i would imagine the switch is there for a reason, similar to how the clutch switch tells the ecu to catch the idle when you press it in.

DaleClark

iTrader: (55)

^Yep, check the neutral switch. If the previous owner tried to bypass the "push down the clutch to start the car" it would have been done at the clutch pedal.

If the car has/had a fancy car alarm with remote start sometimes they have to be wired into the neutral switch so it makes sure the car isn't in gear when it does a remote start. FYI those remote start systems are nothing but trouble, every car I've ever seen with those alarms had all sorts of weird electrical issues.

Dale

Djseto

iTrader: (2)

Ill check. The car doesn't have any aftermarket alarm. Stock one is still there (and works).

Orbitalmovment

iTrader: (2)

Aren't Mazda specs VTA1 = .10 - .70 and VTA2 = .75 - 1.25?

Also you may want to check your coils. I had an issue where my idle would bounce up and down but idle perfectly fine with A/C turned on. After looking for vacuum leaks repeatedly and adjusting my idle every which way 10 times I came across this thread where they had the same problem and ended up fixing the problem by replacing the coils. I replaced my coils with the SBG ignition system and it fixed my idle issues.

Djseto

iTrader: (2)

So I think I got to the cause of my issue. When I checked the dashpot a few weeks back, I confirmed that when you press it, it pushes back. What I didn't do was confirm that when the throttle was closed that it was actually pushing on the pot a little. This is because at that time, I didn't know how the pot actually worked as part of the system. Was talking to Rotorsports Racing yesterday about some other things I had questions about and when I told him about that problem, he said to make sure the metal plate that pushed agains the pot is actually depressing it. He said the dashpot is essentially a dampener so when you come off the throttle, it allows the throttle plate to slowly close vs slam shut. Upon inspection, mine was touching the put, but not pushing against it. I loosened the nut, turned her a bit, and then went for a drive. During my 30 minute drive, the idles were smooth and she never once tried to drop into the low 600RPM when I put her in neutral. Will need to drive some more today, but so far, so good. Of course I just got my datalogit in the mail that I thought I'd need to troubleshoot...

SpinningDorito

iTrader: (2)

This thread is a great summary of all the troubleshooting steps for idle. I've been working out my idle issues and after reading this my dashpot and idle bleed screw were way out of adjustment. The plunger on my neutral switch is also broken, so the pedal was never engaging it. Still have some issues, but definitely seeing some improvements.

Stock ECU must have pretty robust idling logic that was compensating for all this stuff.