ZOMG! Idle solved, S4 turbo owners read inside!
10-10-07, 10:05 PM
#1
Epitrochoid Chamber FTW
Thread Starter
ZOMG! Idle solved, S4 turbo owners read inside!
Today is momentus to say the least. In 4 years of owning my car I have just now achived perfection in tuning, including solving my idle woes!
This set-up is for people who are inbetween stock TB and the TB mod. Sort of a gray area if you will. To be more specific...
This is for those who have removed their vacuum rack/ACV/EGR etc...
Also you have to have severed & capped the coolant line that runs from the top of the engine block to the thermowax behind the TB (for ease of maintenance really). There is some misinformation out there, that the purpose of this coolant line is to cool the TB... LOL it's not, it's to make the Thermowax piston extend and roll the cam roller off of the fast idle cam. Once this happens (the car is now "warm") the throttle plates are allowed to close fully and in a perfect stock RX, the idle would settle to 750. This is when one should set the TPS and why "they" say to warm up the engine first.
I personally, chose not to do the TB mod so that ideally I would retain the cars smoothness at low speeds, to keep it stock feeling.
Problem is... With that coolant line capped, the thermowax thinks the engine is cold all the time and never gets to do it's job, making it next to impossible to set the BAC and TPS properly. Thus, the surging idle insues, bucking at low rpms and all sorts of things that suck. And, not to mention it makes your car look and sound crappy to your bros and to hot chicks :P
Here is the fix I discovered through lots of reseach and some trial and error.
First, remove your IC and get to your TB... Refer to picture 1 for this step.
The screw on the left I've highlighted has a spring between the head of the screw and the the fast idle cam. Unscrew this (counter-clockwise) all the way out, being VERY careful not to drop it once it comes loose. Remove the spring from the screw and set it aside neatly so as not to lose it, in-case you want to undo this *mod* later.
Now, thread it back into it hole and screw it all the way down. Check to make sure the cam has seperated from the roller, if it hasn't, further adjustment can be made with the cam roller adjustment screw, designated on the right side of my pic.
With the roller seperated, you are now simulating a "warm" engine. This is assuming all of your other adjustments are in proper order... Throttle cable, butterfly plate clearances, etc... Verify this by looking at the throttle stop screw and the tab that mates with it. Refer to picture 2, courtesy of NJGreenBud :P Now, if there is a gap, DO NOT adjust the screw to meet the tab. Adjust whatever is making your throttle stick open so that the tab flushes up to the screw.
Now you are ready to set the TPS, there are many methods available. I prefer the DMM method courtesy of FC3SPRO http://fc3spro.com/TECH/HOWTO/TPS/tps.html (THANKS TED!)
Reinstall the IC and MAKE SURE all your IC conections are tight.
Get your flathead screwdriver and adjust the BAC valve screw all the way out.
Start the car. Once the idle settles, attempt to adjust it to 750 via the BAC.
Mine was a little bit weak, even with the BAC screw all the way out. It was around 500-550 rpms, though turning on the AC/headlights, radio etc. verified that my BAC was working properly because it compesated nicely. Though I didn't want to have to keep the AC running to prevent my car from dying :P
If you suffer the same symptoms, proceed to the next step.
Remove the IC again.
Using some chalk and/or a permanent marker to make some marks on the throttle stop screws THREADS to note it's original position, this again is so that if you ever choose to undo this mod, you can easily.
Unplug your TPS and connect your DMM as if to set it per normal, it should read close to 1k-Ohm, keep it within eyeshot to give you a "barometer" on how much you are adjusting the idle speed while you are turning the throttle stop screw.
Now, loosen the 8mm lock nut on the throttle stop screw and start threading so that your reading on the DMM gets higher. When you are satisfied that you have compensated sufficiently, tighten up the locknut and then reset the TPS back to 1k-Ohm.
Plug it all back together, reinstall the IC and fire her up, keeping your flathead handy. Again now, you should be able to fine tune the idle to 750 via the BAC valve adjustment screw.
If your still off by small margin repeat the previous step until you arrive within a comfortable range for the BAC adjusment screw. Alternativly, you could unplug the BAC (or jumper the intial set coupler) during this step. This would (for me at least) involve ALOT of taking off and putting back on of the IC. I need one of those sweet PVC rigs that you can temporarily replace the IC with for idle tuning.
That about does it... This information again was a SERIOUS compilation of reading tons of threads about this sort of problem. I will link some of them here for those of you that this didn't work for. Good luck and DRIVE HARD!
Good pics in this one and some movies of the bad idle symptoms. Lotsa good info here! https://www.rx7club.com/2nd-generation-specific-1986-1992-17/video-still-crappy-idle-no-response-idle-adjustment-657023/
Archive thread about idle faq. This helps to rule out Vacuum leaks, IMPORTANT!
https://www.rx7club.com/2nd-gen-archive-72/faq-idle-problems-334730/
Archive thread to remove emissions, (often a source of vac leaks)
https://www.rx7club.com/2nd-gen-archive-72/emissions-equipment-what-you-can-remove-how-112251/
Also, FYI... Just yesterday, I completed the super grounding job discussed in the archive. Some people have claimed that doing this helped settle their troublesome idles. I strongly suggest that anyone with some experience in soldering perform this job! You won't regret it!!
https://www.rx7club.com/2nd-gen-archive-72/grounding-how-thorough-discriptive-199558/
Word...
This set-up is for people who are inbetween stock TB and the TB mod. Sort of a gray area if you will. To be more specific...
This is for those who have removed their vacuum rack/ACV/EGR etc...
Also you have to have severed & capped the coolant line that runs from the top of the engine block to the thermowax behind the TB (for ease of maintenance really). There is some misinformation out there, that the purpose of this coolant line is to cool the TB... LOL it's not, it's to make the Thermowax piston extend and roll the cam roller off of the fast idle cam. Once this happens (the car is now "warm") the throttle plates are allowed to close fully and in a perfect stock RX, the idle would settle to 750. This is when one should set the TPS and why "they" say to warm up the engine first.
I personally, chose not to do the TB mod so that ideally I would retain the cars smoothness at low speeds, to keep it stock feeling.
Problem is... With that coolant line capped, the thermowax thinks the engine is cold all the time and never gets to do it's job, making it next to impossible to set the BAC and TPS properly. Thus, the surging idle insues, bucking at low rpms and all sorts of things that suck. And, not to mention it makes your car look and sound crappy to your bros and to hot chicks :P
Here is the fix I discovered through lots of reseach and some trial and error.
First, remove your IC and get to your TB... Refer to picture 1 for this step.
The screw on the left I've highlighted has a spring between the head of the screw and the the fast idle cam. Unscrew this (counter-clockwise) all the way out, being VERY careful not to drop it once it comes loose. Remove the spring from the screw and set it aside neatly so as not to lose it, in-case you want to undo this *mod* later.
Now, thread it back into it hole and screw it all the way down. Check to make sure the cam has seperated from the roller, if it hasn't, further adjustment can be made with the cam roller adjustment screw, designated on the right side of my pic.
With the roller seperated, you are now simulating a "warm" engine. This is assuming all of your other adjustments are in proper order... Throttle cable, butterfly plate clearances, etc... Verify this by looking at the throttle stop screw and the tab that mates with it. Refer to picture 2, courtesy of NJGreenBud :P Now, if there is a gap, DO NOT adjust the screw to meet the tab. Adjust whatever is making your throttle stick open so that the tab flushes up to the screw.
Now you are ready to set the TPS, there are many methods available. I prefer the DMM method courtesy of FC3SPRO http://fc3spro.com/TECH/HOWTO/TPS/tps.html (THANKS TED!)
Reinstall the IC and MAKE SURE all your IC conections are tight.
Get your flathead screwdriver and adjust the BAC valve screw all the way out.
Start the car. Once the idle settles, attempt to adjust it to 750 via the BAC.
Mine was a little bit weak, even with the BAC screw all the way out. It was around 500-550 rpms, though turning on the AC/headlights, radio etc. verified that my BAC was working properly because it compesated nicely. Though I didn't want to have to keep the AC running to prevent my car from dying :P
If you suffer the same symptoms, proceed to the next step.
Remove the IC again.
Using some chalk and/or a permanent marker to make some marks on the throttle stop screws THREADS to note it's original position, this again is so that if you ever choose to undo this mod, you can easily.
Unplug your TPS and connect your DMM as if to set it per normal, it should read close to 1k-Ohm, keep it within eyeshot to give you a "barometer" on how much you are adjusting the idle speed while you are turning the throttle stop screw.
Now, loosen the 8mm lock nut on the throttle stop screw and start threading so that your reading on the DMM gets higher. When you are satisfied that you have compensated sufficiently, tighten up the locknut and then reset the TPS back to 1k-Ohm.
Plug it all back together, reinstall the IC and fire her up, keeping your flathead handy. Again now, you should be able to fine tune the idle to 750 via the BAC valve adjustment screw.
If your still off by small margin repeat the previous step until you arrive within a comfortable range for the BAC adjusment screw. Alternativly, you could unplug the BAC (or jumper the intial set coupler) during this step. This would (for me at least) involve ALOT of taking off and putting back on of the IC. I need one of those sweet PVC rigs that you can temporarily replace the IC with for idle tuning.
That about does it... This information again was a SERIOUS compilation of reading tons of threads about this sort of problem. I will link some of them here for those of you that this didn't work for. Good luck and DRIVE HARD!
Good pics in this one and some movies of the bad idle symptoms. Lotsa good info here! https://www.rx7club.com/2nd-generation-specific-1986-1992-17/video-still-crappy-idle-no-response-idle-adjustment-657023/
Archive thread about idle faq. This helps to rule out Vacuum leaks, IMPORTANT!
https://www.rx7club.com/2nd-gen-archive-72/faq-idle-problems-334730/
Archive thread to remove emissions, (often a source of vac leaks)
https://www.rx7club.com/2nd-gen-archive-72/emissions-equipment-what-you-can-remove-how-112251/
Also, FYI... Just yesterday, I completed the super grounding job discussed in the archive. Some people have claimed that doing this helped settle their troublesome idles. I strongly suggest that anyone with some experience in soldering perform this job! You won't regret it!!
https://www.rx7club.com/2nd-gen-archive-72/grounding-how-thorough-discriptive-199558/
Word...
Last edited by Rotaryrockstar; 10-10-07 at 10:10 PM.
10-10-07, 10:42 PM
#2
Why didn't you just remove the thermowax (if you've got no coolant routed through it) and disable all of it's nonsense by simply getting rid of it... Also helps with some of the clutter behind the UIM. Both Ted and Kevin Landers website have decent info and pics that work well complementary for removing the thermowax (among other things).
Even though you have the benefit of the adjustable BAC, you might want to consider jumpering the initial-set coupler, setting the idle RPM via the idle-adjust screw and then tune it "down" with the BAC after you've removed the initial set-coupler--just so you're not solely relying on the BAC for idle-control...
Just a thought.
Even though you have the benefit of the adjustable BAC, you might want to consider jumpering the initial-set coupler, setting the idle RPM via the idle-adjust screw and then tune it "down" with the BAC after you've removed the initial set-coupler--just so you're not solely relying on the BAC for idle-control...
Just a thought.
10-10-07, 10:49 PM
#3
Epitrochoid Chamber FTW
Thread Starter
Being that it IS a 10th AE, I'm reluctant to do anything truly permanent. I haven't read the write-ups on removing the thermowax, though I would assume there is some pluging of holes using things such JB weld or RTV yeah?
I actually purchased a replacement coolant hose from mazdatrix, but I think they sent me the wrong one. I intended to put it back on which is why I kept the Thermowax there.
In response to your suggestion about setting w/o the BAC running, I mentioned that as an alternative toward the end of my thread, if you read that far :P I know it's lengthy, however, I know that I always appreciate it when people are thorough and descriptive.
I actually purchased a replacement coolant hose from mazdatrix, but I think they sent me the wrong one. I intended to put it back on which is why I kept the Thermowax there.
In response to your suggestion about setting w/o the BAC running, I mentioned that as an alternative toward the end of my thread, if you read that far :P I know it's lengthy, however, I know that I always appreciate it when people are thorough and descriptive.
10-10-07, 10:53 PM
#4
Being that it IS a 10th AE, I'm reluctant to do anything truly permanent. I haven't read the write-ups on removing the thermowax, though I would assume there is some pluging of holes using things such JB weld or RTV yeah?
I actually purchased a replacement coolant hose from mazdatrix, but I think they sent me the wrong one. I intended to put it back on which is why I kept the Thermowax there.
I actually purchased a replacement coolant hose from mazdatrix, but I think they sent me the wrong one. I intended to put it back on which is why I kept the Thermowax there.
10-10-07, 10:57 PM
#5
Epitrochoid Chamber FTW
Thread Starter
04-27-08, 10:49 AM
#7
Good post. Personally I think you should remove the thermowax if you don't have the coolant line on there.
But I have used your strategy of tuning that screw by using TPS voltage (you used resistance, not a big difference) as a benchmark. I have a FMIC so I tune that screw with the car running sometimes. Another thing you could do is build a crossover pipe out of home depot piping to give you access to that stuff with the car running (just for diagnostic purposes), as long as you can make it not leak air.
I also went to mention that I have the opposite setup as you. I have no BAC but I have retained my fast idle cam, thermowax, and coolant line. I have the OEM coolant line on the rear iron, and then I just used parts store hose to run the coolant from the TB directly to the waterpump, bypassing a BAC.
In this way I still have a higher, more stable idle when cold without the complexity of the BAC's plumbing. The trick with that is to make sure that the fast idle cam adjuster screw with the spring is turned just about all the way OUT, but not removed. Only do this if your cold idle is too low, otherwise leave it alone. Then fiddle with the throttle stop screw once the car is warmed up. And when you tighten that 8mm nut it will tighten the screw a little more than you wanted to if you are not careful. After you are satisified with your cold idle and warm idle, set your TPS.
But I have used your strategy of tuning that screw by using TPS voltage (you used resistance, not a big difference) as a benchmark. I have a FMIC so I tune that screw with the car running sometimes. Another thing you could do is build a crossover pipe out of home depot piping to give you access to that stuff with the car running (just for diagnostic purposes), as long as you can make it not leak air.
I also went to mention that I have the opposite setup as you. I have no BAC but I have retained my fast idle cam, thermowax, and coolant line. I have the OEM coolant line on the rear iron, and then I just used parts store hose to run the coolant from the TB directly to the waterpump, bypassing a BAC.
In this way I still have a higher, more stable idle when cold without the complexity of the BAC's plumbing. The trick with that is to make sure that the fast idle cam adjuster screw with the spring is turned just about all the way OUT, but not removed. Only do this if your cold idle is too low, otherwise leave it alone. Then fiddle with the throttle stop screw once the car is warmed up. And when you tighten that 8mm nut it will tighten the screw a little more than you wanted to if you are not careful. After you are satisified with your cold idle and warm idle, set your TPS.
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