Yes, I searched. I read multiple posts from @DaleClark and also read the recent post that @scotty305 gave some good insight. I didn't wanna add to that post because my behavior is different. I pulled my IACV and cleaned it per @DaleClark instructions and I verified it worked by applying 12V to it. So here we go...

In the process of trying to figure out why my car would stall with AC running while in neutral (just got AC installed), I discovered that my IACV wasn't working. I was getting zero volts at the B/W wire and no continuity between the L/G wire to pin 4Q on the engine management connector. This car was single turbo when I got it so I have no idea what the previous owner cut. I tapped 12V from the Turbo Precontrol B/W wire since it was confirmed to still be hot and the connector was not in use. I then ran a direct wire from 4Q to the IACV plug and confirmed continuity. My ECU is a PowerFC and engine is street ported.

Before I noticed this, my car idled great at around 1000rpm. The idle was set by @rotorsportracing and I haven't made any manual adjustments. Per @DaleClark 's old posts, I reset my PFC (and then loaded my map) and tried to do the idle learn process. When I turned the car on to learn, it would stay at 2300-2500 RPM. It would NEVER drop down to the 1000RPM range for the first 20 min (10 min of idle + 10min of idle and rear defrost so it could learn with electrical load) and it would NEVER hunt for idle. When I turned the AC on, it would drop about 300rpm but still no hunting.

If unplugged the IACV, RPM would drop to my pre-IACV range, but as soon as I plugged it in, it jumped back up. I let it "learn" anyways, went for a test drive and my car did not stall with AC running but this was also because my car would idle around 2000-2100RPM. When my car was stalling, it would idle around 1000rpm with no AC and then when the AC was on, it would drop to 600-700 and eventually die unless I turned the AC off. This was when I started to wonder if the IACV was working because making adjustment to AC idle in PFC didn't do anything.

So I get home from my test drive, disconnected the IACV, the idle drops to 1000. I plug the IACV back in and boom, it starts hunting. Why it wasn't hunting before I have no idea. I read the post above and I back probed the L/G wire so I could measure the voltage per @scotty305 . My IACV measured at 10V. When it was hunting it would fluctuate between 8-9V. OK, so now I know the IACV is "working". Still..my idle is way high.

Now for the really weird part, I reset my PFC again so I could start the learn process. When I started the car up, it ran around 2300rpm and would drop down a 1500-1700rpm and start to hunt. OK ... so this is progress I think. But, unlike the first learn, my car was nice and warmed up vs being cold. Not sure if that explains why the RPM dropped. I realized while it was hunting that I forgot to plug my power commander in. As SOON as I plugged the Power Commander in, my idle JUMPED back to 2500pm. I unplug the PC and it drops down, goes to hunt. Plug the PC back in and it jumps again. Basically, anytime I plugged the PC in, the RPM levels would jump. WTF

I am complete and utterly effing confused. I don't understand how plugging my PC in is causing the RPM to jump, but it absolutely is. So I don't know if my PFC is bad, my PC is bad, my IAC is bad?

I will test it all again tomorrow morning when the car is cold, but I suspect like today it will just stay pegged at 2500rpm like it did with my first learn. It's almost as if if my car never got out of that cold startup RPM range the first time I tried to learn. I may try without the PC, but the issue is that my Tach is slightly off so I rely on the PC for an accurate RPM reading. I do have the a dataloggit so maybe I watch my RPM there? I just dont get how the PC causes the RPM to rise.... I'm lost. Need help

 

You're making this harder than it needs to be.

Think about it. Idle is set by air getting around the throttle plates into the engine. If you have the throttle plates closed, the engine gets no air and you have no idle at all, the car would stall as soon as you let your foot off the gas.

Your ISC was totally non-functional previously. That means something was getting 1000 rpm of air into the engine since the ISC was shut. Now that you have the ISC working it's adding air on top of that 1000 RPM of air. The PFC is trying to figure out how to get the idle right so it's all over the place but it can't do it since you have that extra air getting in.

Most likely the throttle stop screws have been adjusted to crack the throttle open slightly with the throttle closed. For the ISC to work properly the throttle plates should be shut.

There is an adjustment screw for the ISC under the entrance to the throttle body, this is the screw you adult a half turn from closed as in the PFC FAQ. I would also check that screw, that sets how much air the ISC gets to work with. That half turn from closed typically works fine.

Start with making sure your throttle plates are shut. If it's not that, there's some other vacuum leak or something going on. Remember, air is getting past the throttle plates somehow, you have to find that air that's getting in and raising the idle.

Dale

 

Thanks @DaleClark I'll check that out first.

I have another possible cause that maybe you can help me figure out. My car's OEM fan controller doesn't work so I have an aftermarket one that uses a probe in the radiator that kicks on based on the probes temp that I can set. I still have stock fans but because the aftermarket is on or off, the fans wired so when they are on, both fans run at MAX speed.

I have my controller set to kick on at round 82c and when they run, they cool the car down fast (running Greddy VMount Kit). After reading the Big Fat FD3S cooling thread, it appears that at 82, the car is just barely warming up and the Thermostat starts to crack open. I noticed last night that my coolant temps once the fans kicked on, never got past 80 once the fans kicked on while the car was idling. From what I've been reading, the cold start RPM is driven by coolant temp. If my coolant temp never rises high enough because may fans are on too early (and doing a really good job), then I'll never leave the cold start RPM range. Does this sound plausible?

I looked in my PFC settings, and Fan1 is set to 86 and Fan2 is set to 89. In my case, I can't control them separately. That being said, what's a good temp to have my fans kick on and what's a normal coolant temp for driving? I've been thinking lower is better, but now I'm wondering if I'm way too low?

I still can't wrap my head around why plugging the PC in causes the jump in RPM though...

 

I would probably crank the fans up to kick on at 90 deg C and kick off at 85. Around 85 is a very happy range to be in.

With the AC you will want the fans to run whenever the AC runs.

The fans are 3-speed, I don't know how they are set with the fan controller. That said, I would probably see if you could wire the fans to run at low speed with the AC on, and then kick up another speed if the car gets to 90 deg. C

Also the 93-95 ECU's only have 1 fan output. The later ECU's have 2 outputs to run the fans, that's why there are 2 speeds in the PFC. On yours only the first will do anything, I usually set them both the same just to do it. That said, I think all it does is just trigger the fans at that speed, if you aren't using the OEM relays/wiring it won't do anything. I don't think the PFC accounts for "fans should be on so I should do x with idle" or anything.

Regardless, some of this is down the road and not related to your current issue you're working on. Bump the fans up a bit and continue working on your idle.

Took me a bit to get PC = Power Commander. Typically you would just call it the Commander, no abbreviation needed. Anyhow, it's not a great idea to plug and unplug the Commander with the car on, not sure why it's doing anything but I wouldn't get too deep into that rabbit hole.

Dale

 

I dont have much control with the external fan controller. It's basically ON or OFF based on the temp probe and there is a override wire that you can wire to the AC compressor wire so it kicks on when the AC is running regardless of temp. I can't set on and off speed, on the speed that triggers them on. I'll set them to 86. When it hits 86, they would kick on. When the temp drops below 86, they kick off. I can't set on ad 90 and off at 85. Im sure such fan controller exists somewhere, but it's probably pricey compared to this $50 universal one.

I am not using any of the OEM relays but they are still there. The wiring for OEM fan control was hacked up by the previous owner and it had aftermarket fans. I bought OEM fans and then just wired them together such that they are always running MAX speed when the fan is on since I didn't have the capability to control them like the OE. Thanks for your input as always. I'm going to get to the garage and adjust idle and fan settings. Hopefully it works...then I'll just see what shoe falls off next.

 

@DaleClark for the win! I adjusted the throttle plate screw as it was cracking the throttle open. I went full close on the throttle plate and it dropped the idle down so that the ISC could do its thing. I also recalibrated the TPS voltage since adjusting the throttle plate shifted my values. I ran the learning and the car is doing great with Idle...for the most part but the ISC works and adjusting settings in the Commander now work!

My next issue is my fans I think. I adjusted the fans to come on at 88 degrees and at full blast, it cools down a few degrees pretty quickly. The issue I noticed today was that it was relatively cool out (high 70's but humid) and I still ran the AC. With the AC on, the fans run full blast and given the ambient temp plus the fans full blast, my coolant temp dropped down to about 80c. At 80c, whenever I came to a light, my RPM was in the 1500 range and the car would hunt for idle...after 15-20 seconds of hunting, it would level out at 1500. My *guess* is that with water temp being 80c, it thinks the car isn't warmed up and is therefore raising idle to warm up the car. If I drove the car hard and got the water temp to be 85+, the car would idle perfectly around 970-990 RPM (it's set for 980RPM) with the AC.

This is a big win for me. 2 years and I never know my ISC wasn't working. I'd like about 40 hours of my life back troubleshooting AC and other random idle issues...

I think my next project will be to see if I can wire the OEM fans to work with the ECU since it will probably fix my issue...

 

I am having a similar issue, and I am not sure if it is my IACV or not. Long story short I recently had powdercoated uim, throttle body, y-pipe and its intake counterpart, as well as swapped the pulleys. Needless to say i removed and took apart A LOT of things and springs. The car was off the battery for about a month and a half while i got all the parts to come back to me. I was very careful about returning all the vacuum hoses and the sort back to their proper locations. I even replaced broken ones with silicone hoses.In the process I botched the soldering of my alternator and fried regulate and/or recitifier so it was overcharging initially. I just replaced alternator for now to get to this idle problem. I have the elbow off and checked the plates were shut, and i did tighten down the throttle screw on the bottem to fully closed and that maybe dropped it to 1750-1800 rpms. I also checked the IACV resistance and it was at 13.4 ohms but this was measured after the engine was warmed up and not at the 20c it was supposed to be measured. I really don't want to have to replace that valve. This has a FEED built engine so it is running a PFC. I was wondering if it may have re-learn idle ( I can't imagine this thing not having EPROM or something but...). Im still digging in forums at other people having similar issue.


That rear plate may not be in the proper position


This white powder might be a coolant leak somewhere but i don't see any visible leaks from anything.

 

You didn't say what your idle is doing - too high, too low, what?

Also does the car generally start and run OK?

Dale

 

To fully get this tuned right you really should have a datalogit and a wideband and actually tune everything. That means you need to look at the idle speed and fuel cut settings, read the idle duty cycle from the PFC (only possible with datalogit). You also have the physical dashpot on the throttlebody.

This complication is why the quick(er) fix is to basically disable the IACV and adjust a few screws. It doesn't actually idle like stock when you do it that way, but it's the quick fix. It's also why every new car for the past 12ish years has come with electronic throttle, because idle control on cable throttles are complicated.

more discussion in this thread: https://www.rx7club.com/3rd-generati...needed-841706/

I think my threads are so old they don't even show up in search anymore, although I think that one's archived.

 

Dale sorry it generally did before i started this project… even with the split and cracked hoses i found on turbo actuators etc. Right now it idles at 1800ish rpms. Before it was like 750 800 range. And dropped to this at 71celcius.

I'll have to do a lot more research on this. I am not savvy on tuner side of this. The PFC was installed and tuned by FEEDs Fujita and worked properly before my engine room projects

 

If you idle is that high air is getting in where it shouldn't somewhere. The ISC can't do an idle that high. You'll have to find where the air is getting in and solve that problem - bad lower intake manifold gasket, vacuum lines to lower or upper intake manifold open to atmosphere, throttle plates stuck open.

Also if you had the throttle body powder coated it's possible the shaft seals on the throttle body are missing or failed. There's a writeup about those seals just a few months back, search for it. I would be suspicious of the throttle body since you have to big time take it apart and put it together to powder coat and the TB is a VERY complicated device. Quite possible it's not sealing properly.

Get a can of starting fluid and spray where you think a leak may be - the idle will rev up and smooth out when it sucks that fluid in.

Hopefully it's something easy, just have to find it.

Dale

 

@DaleClark You're definitely not kidding about it being complicated...When it came time to put it back together I referenced a lot (threads, original photos, manual..etc). I can see why people just swap it out. I did check the spring and butterfly operation. The seals...are those the little rubber grommets? I think those went back in the right place. As far as the seals go, I wasn't the one to take them out BUT I was the one putting everything back together. For the powdercoater I stripped everything down to whatever was able to take the heat (but powdercoater found those and pulled the shaft out from UIM). I did make sure he didn't powder anything that was to make a seal or mate with a gasket. However since you mention seals, on the UIM I did put some rubber pieces back together in an unknown fashion.

Gaskets....I changed UIM gasket to throttle body and lower intake manifold. I also swapped the y-pipe to the later gen model as well as that intake pipe that mates with it (and all its related gaskets too). These gaskets were new...but they were ordered using a US parts manual number ( I know i gotta be careful doing this because even though the parts pop up here in Japan..They're sometimes off).

Update on the IAC, its resistance checks out fine at cooled down temp.

I saw you said something similar to someone in another thread about air getting past throttle and ECU trying to compensate for the 1000rpms worth, which has me racking my brain as to what i missed. Now that UIM seal is suspect to me because of my ignorance in assembling it. Gaskets i don't know how i feel about tightening some more...I have the worst luck with stripping and snapping bolts..

Vacuum lines i did look over again this morning when I checked resistance on IAC and their locations still checked out.

One random, possibly stupid question, but @arghx was mentioning about learning idle. I am saving as a last extreme resort, but question is can the PFC forget a tune just from being powered down for a month or so? Don't these things have like EEPROM chips in them too or something of the sort? The car has been tuned so...

 

There's no way the ISC can get your idle that high by itself. The only way you can get it up that high is a leak somewhere.

The good thing is the leak is going to be somewhere from the throttle body to the engine. Anything in front of the throttle body doesn't matter - turbo intakes, Y-pipe, intercooler piping, etc. - none of that matters as far as idle is concerned.

Take the throttle body off and shine a light behind the throttle plates. If you see light coming around the throttle plates they are cracked open and letting air through. Adjust the throttle stop to get them to be fully closed. NOTE: the thermowax on the back of the throttle body will crack the plates open for a 1500 RPM idle when the engine is cold and drop the idle as it warms up. If you have that system on the TB, you need to disengage it to check to see if the plates are closed.

If that doesn't bear fruit, use my starting fluid trick to spray around to find where the leak is.

Dale

 

a cliff notes version is that with a stock car, the BAC valve is set up to not have a ton of control. Mazda figured out that using air is slow (and it has emissions implications at some point), so the stock ECU uses timing to make quick changes to idle speed, and the BAC will follow.

when you jump the TEN (Test Enable) and GND (Ground), you turn off the timing feedback.

TL;DR? the engine idle is set to ~700rpm mechanically, the BAC brings it up to 750, and then the timing will keep it there if you don't have the mechanical idle speed right, the BAC can't help you, it will surge and hunt and do other weird things

 

I'm in the "you have a leak" camp. Making changes to the throttlebody is one of the trickier things to do on these cars and there's a lot that can go wrong. It's basically an old carburetor without actually dripping fuel.

 

Ok I will get on this first thing after breakfast tomorrow morning. I am hoping that leak is not in those seals… lol i made a promise to myself not to touch any of that stuff again without having a garage or something similar. Occupied my apt for a whole month waiting on parts from around the planet. ( T∀T)

 

im going to have to find starter fluid somewhere. I bought carb cleaner bc thats all i found but thats not safe on the powdercoated stuff…I know we isolated the area but there is way too many parts that can lead me astray. I am tempted to pull uim and throttle out again and rerun through it all but my time is running out. School starts next week… after that all i'll have time for is routine maintenance. Which runs me into winter and spring… also a no car work period (stuff ALWAYS breaks on me in the cold)

Quick question… does anyone know if the throttle plates in the uim is normally open or closed? I think those may be installed wrong idk…

 

The throttle plates that aren't in the throttle body that are in the UIM are the Double Throttle. All this is for is to restrict air Into the engine when the engine is cold and also cars with automatics use this somehow when shifting gears (I don't know automatic stuff that well on purpose )

Anyhow, they are typically full open during normal driving, only closed when the engine is cold (like under 50 deg. C or so). It doesn't matter if they aren't fully closed or whatever. Actually a lot of people just remove them to clean things up.

Starter fluid is sometimes called "ether" as well. I always recommend it for finding vacuum leaks since it evaporates VERY quickly and doesn't leave a flammable substance behind. You can use carb cleaner/brake cleaner but they can leave stains and they can pool up and I don't like flammable stuff pooling up on a running engine.

Dale

 

Today I took uim and throttle body out of car.I will do light check on plates and stuff.

I'll check rats nest to uim lines once evening comes around cause its way too hot outside right now. The uim and tb I will check and double check… if somehow it all works when i reinstall well then idk i'd still be confused but maybe it was something i rookie put back together.
And i HATE coolant (/ー￣

once im sorted i want to delete as much… or have complete control over all the coolant paths out of engine.

 

 

@DaleClark You're a bloody genius mate. Idle is now down to 950 give or take a 100 at times. I did the light test and primary throttle was not shut whatsoever so i pulled apart the right side of the throttle body that pertained to the primary throttle shaft and adjusted things around till it can close properly. The fast idle cam components were too engaged. I also adjusted the double throttle in the uim so those shut properly when they're suppose to. I notices when I shut it manually it wasn't closing all the way ( I know you said not necessary but figured why not while its all apart). Rats nest and lines too and from uim were fine. Idle is 99% sorted but I created 2 new problems lol. Heat warning on dash is now on (Although this started yesterday, not today when I took everything apart), and car stalls out when trying to drive off in gear.

If the heat warning is due to the cat going, then its fine...I just need that thing to hang on long enough to pass inspection in like 2.5 months. Then I don't have to worry about inspection in this country again.

Now the stalling...I put the TPS on while trying to engage the spring thing. This is probably not correct and maybe this is causing it. The first time putting car back together i just put the TPS on without trying to sort out what that crappy lever setup on inside is doing. I'll release it in the morning and see. Hopefully I can go for a day drive with this car before school!

 

Nice, you're chipping away at it! Keep at it!

Dale

 

Ah sorry to keep everyone in the dark, school started and these people are ridiculous with assignments before you even attend first class. Anyway I DID release the TPS from spring loading it (idk why I thought it needed to be in the first place), all I did was take cover slightly off to hear it click to proper place and put it right back on. The car now doesn't stall and the heat warning lamp on dash is extinguished. I took the car for a full day drive across 2 prefectures and up a mountain and it didn't abandon me anywhere lol. There is still a funny whistling mooing when climbing in boost but I think its because of a hose to the BOV that is kind of in a weird angle from being too long with new Y-pipe. I'll sort it out. Thanks for all you wise words everyone.