Persistent Idle Problem
06-08-05, 10:30 PM
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Persistent Idle Problem
I originally sent this to RETed days ago, but I haven't heard back from him yet, so I'm hoping I can get some useful info from the forum in the meantime.
After searching through the rx7club forum and N.P. forum several times over the last few months (as well as the FC3SPRO.com forum) about my idle problem and ways to check everything and possible fixes, I have come up empty handed and I'm still dealing with the same problem.
I have a '91 Mazda RX7 N/A with a rebuilt 6-port streetported engine using RA apex seals and o-ring kit. All other parts are new OEM parts, including OEM apex seal springs. The engine currently has 7,000 miles on it and I am getting a consistent compression reading of about 125 psi on all faces. I have used all new gaskets, and ALL vacuum lines have been replaced with silicone vacuum hose. I have checked several times for vacuum leaks times just in case. Initially, I had to adjust the primary throttle stop screw to keep the engine idling for the first 1500 miles. I set the idle to 1500 rpms. Since then, I pulled off the throttle body and re- adjusted both the primary and secondary throttle stop screws so that the throttle plates would fully close. I then re-adjusted both TPS switches to spec with the thermovalve that opens the throttle "de-activated". I also checked the BAC valve, and it does work and is within spec. After doing this, the car would not idle (sometimes it would, but only for a few seconds). When I would adjust the idle screw on top of the throttle body, the engine would rapidly "hunt" roughly between 500-1500 rpms. After several tries of adjusting it, I still couldn't get the car to hold a good idle. Sometimes, I could get it to hold, but then the engine would sputter and die. If it wasn't spuutering out and dying, it would just "hunt". I have also run a full grounding system using 4 gauge wire that goes from the body of the ECU, to the firewall, to the manifold, to the engine block, to the alternator body, to the chassis, then to the negative battery terminal, just in case of any grounding problems in the electrical system. The ECU does NOT put out any codes. My only temporary fix has been to adjust the primary throttle stop screw to open up the primary plate, and I reset both TPS switches for this. I actually had to remove the nut that's on the throttle stop so that I could thread it in far enough for the engine to hold a decent idle. I've also used REDLINE FUEL SYSTEM CLEANER in the tank for the injectors JUST IN CASE they could be a culprit, but my AFR's read just fine and using the REDLINE made NO difference, which leads me to believe that if I did notice a difference, that the injectors needed to be sent out for cleaning. >>I only visually inspected these during assembly and they were all VERY clean. Since the idle adjustment, I get an inconsistent idle (obviously) that holds anywhere from a steady 650, 750, 850, 950, 1050, 1150, 1350, or even 1450. It always idles at a different speed between stops. Since I have the primary throttle plate adjusted slightly open, it occasionally feels like it's intermittently backfiring upon deceleration, or when I'm extremely light on the throttle, the car starts "bucking" a little. Obviously, this is the deceleration fuel cut kicking in and out caused by the air flow meter>>because the throttle plate is a little open during deceleration, air is still being pulled through the intake during deceleration. I have tried setting the primary throttle stop so that the plate is closed, but I can't find ANY way to keep the car idling. I also made sure that the tiny hole in the center of the primary throttle plate was clear and open. The voltage for the TPS switches were set correctly as per the FSM. I 've checked the "full sweep" of both switches for dead spots and they work just fine, and I've tried adjusting the idle screw, but the car would either "die" or "hunt" at idle. I know it's not the porting because sometimes it will randomly hold a rock solid 700 rpm's at idle. If you want any more info about my engine build, etc, I will gladly let you know if it will help you to aid me in diagnosing my idle problem.
I also have a Racing Beat header and presilencer, an Apexi' S-AFC, and an Innovate Motorsports Air/fuel ratio monitor. I also wanted to ask about what you guys suggest for AFR's to shoot for, for my N/A application. Currently, I have the AFR's running in the low 14's.)
Best Regards,
Brian
After searching through the rx7club forum and N.P. forum several times over the last few months (as well as the FC3SPRO.com forum) about my idle problem and ways to check everything and possible fixes, I have come up empty handed and I'm still dealing with the same problem.
I have a '91 Mazda RX7 N/A with a rebuilt 6-port streetported engine using RA apex seals and o-ring kit. All other parts are new OEM parts, including OEM apex seal springs. The engine currently has 7,000 miles on it and I am getting a consistent compression reading of about 125 psi on all faces. I have used all new gaskets, and ALL vacuum lines have been replaced with silicone vacuum hose. I have checked several times for vacuum leaks times just in case. Initially, I had to adjust the primary throttle stop screw to keep the engine idling for the first 1500 miles. I set the idle to 1500 rpms. Since then, I pulled off the throttle body and re- adjusted both the primary and secondary throttle stop screws so that the throttle plates would fully close. I then re-adjusted both TPS switches to spec with the thermovalve that opens the throttle "de-activated". I also checked the BAC valve, and it does work and is within spec. After doing this, the car would not idle (sometimes it would, but only for a few seconds). When I would adjust the idle screw on top of the throttle body, the engine would rapidly "hunt" roughly between 500-1500 rpms. After several tries of adjusting it, I still couldn't get the car to hold a good idle. Sometimes, I could get it to hold, but then the engine would sputter and die. If it wasn't spuutering out and dying, it would just "hunt". I have also run a full grounding system using 4 gauge wire that goes from the body of the ECU, to the firewall, to the manifold, to the engine block, to the alternator body, to the chassis, then to the negative battery terminal, just in case of any grounding problems in the electrical system. The ECU does NOT put out any codes. My only temporary fix has been to adjust the primary throttle stop screw to open up the primary plate, and I reset both TPS switches for this. I actually had to remove the nut that's on the throttle stop so that I could thread it in far enough for the engine to hold a decent idle. I've also used REDLINE FUEL SYSTEM CLEANER in the tank for the injectors JUST IN CASE they could be a culprit, but my AFR's read just fine and using the REDLINE made NO difference, which leads me to believe that if I did notice a difference, that the injectors needed to be sent out for cleaning. >>I only visually inspected these during assembly and they were all VERY clean. Since the idle adjustment, I get an inconsistent idle (obviously) that holds anywhere from a steady 650, 750, 850, 950, 1050, 1150, 1350, or even 1450. It always idles at a different speed between stops. Since I have the primary throttle plate adjusted slightly open, it occasionally feels like it's intermittently backfiring upon deceleration, or when I'm extremely light on the throttle, the car starts "bucking" a little. Obviously, this is the deceleration fuel cut kicking in and out caused by the air flow meter>>because the throttle plate is a little open during deceleration, air is still being pulled through the intake during deceleration. I have tried setting the primary throttle stop so that the plate is closed, but I can't find ANY way to keep the car idling. I also made sure that the tiny hole in the center of the primary throttle plate was clear and open. The voltage for the TPS switches were set correctly as per the FSM. I 've checked the "full sweep" of both switches for dead spots and they work just fine, and I've tried adjusting the idle screw, but the car would either "die" or "hunt" at idle. I know it's not the porting because sometimes it will randomly hold a rock solid 700 rpm's at idle. If you want any more info about my engine build, etc, I will gladly let you know if it will help you to aid me in diagnosing my idle problem.
I also have a Racing Beat header and presilencer, an Apexi' S-AFC, and an Innovate Motorsports Air/fuel ratio monitor. I also wanted to ask about what you guys suggest for AFR's to shoot for, for my N/A application. Currently, I have the AFR's running in the low 14's.)
Best Regards,
Brian
06-08-05, 11:14 PM
#2
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Man, don't get me started again on installing the extra grounds. Suffice to say, that may be your problem.
If not, are you jumpering the initial set connector when tweaking the mechanical idle? Usually when the idle "hunts", the mechanical idle is set too low and the BAC is popping wide open to try to save her from dying. If in doubt, set the idle adjust screw damn near wide open to see if this helps the "hunting", then tweak her back as necessary...
Oh, and put some spacing in between the paragraphs next time
If not, are you jumpering the initial set connector when tweaking the mechanical idle? Usually when the idle "hunts", the mechanical idle is set too low and the BAC is popping wide open to try to save her from dying. If in doubt, set the idle adjust screw damn near wide open to see if this helps the "hunting", then tweak her back as necessary...
Oh, and put some spacing in between the paragraphs next time
06-09-05, 03:52 AM
#3
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Sorry, once I see it's not a turbo, I don't usually read through it all. 
I just get too many emails and messages, and replying to NA stuff is just not my thing.
If you just cut&paste it like above, it made my head hurt just reading it.
-Ted
I just get too many emails and messages, and replying to NA stuff is just not my thing.
If you just cut&paste it like above, it made my head hurt just reading it.
-Ted
06-09-05, 04:55 AM
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2Lucky2tha7,
my guess is that your airflow meter is sticking or has a dirty feedback pot. See if you can swap it with one of your mates. I have seen this happen with flap type air flow meters. The flap sticks closed and the idle speed increases then the flap flies open and the motor then slows down then the flap closes again and jambs. A bit of RP7 sometimes fixes this but it depends on your AFM it may even damage some AFM's so ask someone first.
Michael Smith
my guess is that your airflow meter is sticking or has a dirty feedback pot. See if you can swap it with one of your mates. I have seen this happen with flap type air flow meters. The flap sticks closed and the idle speed increases then the flap flies open and the motor then slows down then the flap closes again and jambs. A bit of RP7 sometimes fixes this but it depends on your AFM it may even damage some AFM's so ask someone first.
Michael Smith
06-09-05, 06:13 AM
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Originally Posted by 2Lucky2tha7
an Apexi' S-AFC
Can you tell us the settings on the S-AFC???
-Ted
06-09-05, 08:43 AM
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I'd say you have the vacuum lines on the front of the throttle body hooked up *** backwards. My *Guess of the Day*.
If say, you have the line that should be going to the fuel injector air bleeds connected to the nipple on the front of the dynamic chambers VACUUM nipple, that in itself will cause problems similar to what you describe. That line needs to go to the nipple on the dynamic chamber that does NOT have a vacuum.
My *Guess of the DAy* counts on a series five three nipples being the same as a series four's three nipples on the front of the dynamic chamber. Take it for what its worth.
If the Guess of the DAy does not pan out............buy a couple of cans of Starter Fluid. Spray all over the engine at idle, especially where you made blockoff plates. Especially there. Wayne can tell you why you'd especially do that.
If say, you have the line that should be going to the fuel injector air bleeds connected to the nipple on the front of the dynamic chambers VACUUM nipple, that in itself will cause problems similar to what you describe. That line needs to go to the nipple on the dynamic chamber that does NOT have a vacuum.
My *Guess of the DAy* counts on a series five three nipples being the same as a series four's three nipples on the front of the dynamic chamber. Take it for what its worth.
If the Guess of the DAy does not pan out............buy a couple of cans of Starter Fluid. Spray all over the engine at idle, especially where you made blockoff plates. Especially there. Wayne can tell you why you'd especially do that.
Last edited by HAILERS; 06-09-05 at 08:47 AM.
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06-09-05, 10:24 AM
#8
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"Wayne can tell you why you'd especially do that."
You'd have to get her really hot and simulate driving over bumps, too, if you had my problem, lol...Leaking EGR block-off, BTW,is what Hailers is refering to.
It never gave me idle problems, though, and didn't leak until heat soaked...
My "Guess of the Day" is still "Yesterday's Guess of the Day". The hunting idle gives it away. Hunting means the BAC is involved, which means it thinks you're idle is dropping too far...
You'd have to get her really hot and simulate driving over bumps, too, if you had my problem, lol...Leaking EGR block-off, BTW,is what Hailers is refering to.
It never gave me idle problems, though, and didn't leak until heat soaked...
My "Guess of the Day" is still "Yesterday's Guess of the Day". The hunting idle gives it away. Hunting means the BAC is involved, which means it thinks you're idle is dropping too far...
06-09-05, 12:25 PM
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Also spray starter fluid around your fuel injecotors bases. The grommets might be leaking if you used old grommets when reinstalling the injectors.
If you still have a airpump and acv, then spray starter fluid into the airpumps inlet. If the rpms rise at all, then the acv has a leak in it's anti afterburn valve/diaphram.
The bac plug should be pulled off and the idle set to around 750 give or take a hundred. Then reinstall the bac's plug. Make sure all the hose going to the dynamic chamber are arranged as they should be first.
IF that does not work......put it on a box car and send it to Coldspring TX, addressed to The Wayne.
If you still have a airpump and acv, then spray starter fluid into the airpumps inlet. If the rpms rise at all, then the acv has a leak in it's anti afterburn valve/diaphram.
The bac plug should be pulled off and the idle set to around 750 give or take a hundred. Then reinstall the bac's plug. Make sure all the hose going to the dynamic chamber are arranged as they should be first.
IF that does not work......put it on a box car and send it to Coldspring TX, addressed to The Wayne.
06-09-05, 12:45 PM
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Yeah, It definitely looks like one whole sentence. Yes, I did cut and paste, and I will try paragraphs next time for easier reading.
As for the S-AFC settings, I will have to double check that when I have access to my car later on today. I have checked these settings MANY times just to make sure that it wasn't set incorrectly. I have it set exactly the way the manual tells me for a series 5 (89-92) RX7. If I remember correctly, it's set to 4 cyl, arrow pointing upwards, and set to flap.
Why would extra grounds cause a problem? This is definitely a first of what I've heard. I installed the grounds AFTER I discovered the problem by the way.
As for setting the idle adjust screw almost wide open, I will try it again, but I do remember opening it practically all the way and it just kept "hunting".
What do you mean by jumpering the initial set connector by the way? Do you mean the single prong green connector by the battery?
I hardly think that it's the airflow meter. I have checked this a few times for sticking, but it is absolutely clean, and does not stick whatsoever.
As for a possible vacuum leak, I KNOW that this is not the problem. Like I said, I have checked for this several times. The N/A engines hardly have any vacuum lines anyway. I had used all new silicone hosing.
I also double checked with the FSM about the nipples on the dynamic chamber, and they are definitely correct. I also checked the fuel injector air bleeds as well as the oil injector "air lines" for correct hookup.
I have also tried spraying starter fluid EVERYWHERE, but the idle was COMPLETELY unaffected.
I have not used any blockoff plates either.
I have to admit though that I'm not sure if or where the EGR is on my car. Unless, this is where the air control valve is.
My question is:
Can I use blockoff plates considering that I'm still using the stock ECU?? Hell, If I can "bypass" the BAC and/or the air control valve as well as any other components, I will definitely do it if I can get a steady idle that way!! Will doing this affect anything??
Brian
I hope this made for easier reading
As for the S-AFC settings, I will have to double check that when I have access to my car later on today. I have checked these settings MANY times just to make sure that it wasn't set incorrectly. I have it set exactly the way the manual tells me for a series 5 (89-92) RX7. If I remember correctly, it's set to 4 cyl, arrow pointing upwards, and set to flap.
Why would extra grounds cause a problem? This is definitely a first of what I've heard. I installed the grounds AFTER I discovered the problem by the way.
As for setting the idle adjust screw almost wide open, I will try it again, but I do remember opening it practically all the way and it just kept "hunting".
What do you mean by jumpering the initial set connector by the way? Do you mean the single prong green connector by the battery?
I hardly think that it's the airflow meter. I have checked this a few times for sticking, but it is absolutely clean, and does not stick whatsoever.
As for a possible vacuum leak, I KNOW that this is not the problem. Like I said, I have checked for this several times. The N/A engines hardly have any vacuum lines anyway. I had used all new silicone hosing.
I also double checked with the FSM about the nipples on the dynamic chamber, and they are definitely correct. I also checked the fuel injector air bleeds as well as the oil injector "air lines" for correct hookup.
I have also tried spraying starter fluid EVERYWHERE, but the idle was COMPLETELY unaffected.
I have not used any blockoff plates either.
I have to admit though that I'm not sure if or where the EGR is on my car. Unless, this is where the air control valve is.
My question is:
Can I use blockoff plates considering that I'm still using the stock ECU?? Hell, If I can "bypass" the BAC and/or the air control valve as well as any other components, I will definitely do it if I can get a steady idle that way!! Will doing this affect anything??
Brian
I hope this made for easier reading
06-09-05, 12:58 PM
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I also used new grommets and o-rings for all 4 fuel injectors.
Yes, I still have an airpump and ACV. I will spray starter fluid in the airpump inlet at idle and see what happens.
As for unplugging the BAC plug, do you mean the electrical connector for it??
I take it that I should adjust the idle by turning the IDLE ADJUST SCREW on top of the throttle body, and not the throttle stop screw?
I NEED to know what the throttle stop screws need to be set to. Initially, I cleaned the throttle bores and plates and let all 3 plates fully close by loosening the throttle stop screws, then very slightly opening them so that the plates do not "stick".
Is this the correct way to do it??
I also noticed that the BAC valve and gasket have an extra small hole off to the side that the manifold does not cover. Is this normal?
Brian
Yes, I still have an airpump and ACV. I will spray starter fluid in the airpump inlet at idle and see what happens.
As for unplugging the BAC plug, do you mean the electrical connector for it??
I take it that I should adjust the idle by turning the IDLE ADJUST SCREW on top of the throttle body, and not the throttle stop screw?
I NEED to know what the throttle stop screws need to be set to. Initially, I cleaned the throttle bores and plates and let all 3 plates fully close by loosening the throttle stop screws, then very slightly opening them so that the plates do not "stick".
Is this the correct way to do it??
I also noticed that the BAC valve and gasket have an extra small hole off to the side that the manifold does not cover. Is this normal?
Brian
06-09-05, 10:46 PM
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You know what, you did tweak on your throttle stops, didn't you? Now would be a good time to tweak the primary back to FSM specs, I would think.
If you have it closed too much (like all the way), that would accomplish the same thing as having your idle adjust screw too far in.
In any case, if you remove the plug from the BAC (or do the thing with the initial set, I forgot you had an S5) and she dies right away, then your mechanical idle needs some work, either by re-tweaking the plates, or by tweaking the idle adjust screw. Either way you've got to allow some more air into the engine...
FSM gives specs for all of this, BTW...
If you have it closed too much (like all the way), that would accomplish the same thing as having your idle adjust screw too far in.
In any case, if you remove the plug from the BAC (or do the thing with the initial set, I forgot you had an S5) and she dies right away, then your mechanical idle needs some work, either by re-tweaking the plates, or by tweaking the idle adjust screw. Either way you've got to allow some more air into the engine...
FSM gives specs for all of this, BTW...
06-09-05, 11:14 PM
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Thanks for everyone's help, I greatly appreciate it!! I'll be checking this within the next few days and I'll see how it goes. Hopefully, all goes well.
Brian
Brian
06-10-05, 01:07 PM
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I checked the FSM as well as the Haynes manual again to find out the specs for setting the throttle plates, and all it mentions is something about the spacing when the secondaries start to open. There is NOTHING about throttle plate spacing when fully closed. Does anyone know the correct spacing for these??
Brian
Brian
06-10-05, 01:38 PM
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Hmm, that's a good point. I know of the test you speak of, I think I used a drill bit properly sized to check mine once...
Heck, now you got me thinking (a rare thing these days)...Are those bad boys fully closed at idle? Where's Hailers when you need him? He's probably reverse-engineered the throttle linkage some time in the past
Did you ever pull the BAC plug to see if she died?
Heck, now you got me thinking (a rare thing these days)...Are those bad boys fully closed at idle? Where's Hailers when you need him? He's probably reverse-engineered the throttle linkage some time in the past
Did you ever pull the BAC plug to see if she died?
09-10-05, 01:54 PM
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Update: recently, the aluminum bracket that holds my air pump snapped right down the middle somehow. (the belt was relatively tight, but not THAT tight!!). So I said **** it. I removed the air pump and air control valve, and used a block off plate. The idle seems more steady, but sometimes it will idle higher and "hunt". Tapping the gas fixes that however. I never got the idle just right. I guess this is the best I'll get until I get a standalone. I also wired open the auxillaries.
09-13-05, 03:29 AM
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Hunting Idle
Originally Posted by 2Lucky2tha7
Update: recently, the aluminum bracket that holds my air pump snapped right down the middle somehow. (the belt was relatively tight, but not THAT tight!!). So I said **** it. I removed the air pump and air control valve, and used a block off plate. The idle seems more steady, but sometimes it will idle higher and "hunt". Tapping the gas fixes that however. I never got the idle just right. I guess this is the best I'll get until I get a standalone. I also wired open the auxillaries.
09-13-05, 03:26 PM
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Originally Posted by Sideways7
Set the safc to more rich around the idle and see if that helps your idle. If it does, that means that you have a vac leak. The extra fuel would compensate for the afm reading not enough air.
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