Idle Issues Thread
03-03-04, 12:06 PM
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Idle Issues Thread
Hey everyone. I'm a long time reader of this forum, but this is my first post.
I have an 89 GTUs with some idle problems. I've been searching for help but can't find what I'm looking for. Maybe we could make a thread dedicated to adjusting and correcting idle problems? Just a thought.
My problem is this - When the car is cold and I start it, the idle bounces from 1200-1400 rpm. It will continue to do this until the car is warmed up. Once it's warm the car will idle steady around 900.
I have an 89 GTUs with some idle problems. I've been searching for help but can't find what I'm looking for. Maybe we could make a thread dedicated to adjusting and correcting idle problems? Just a thought.
My problem is this - When the car is cold and I start it, the idle bounces from 1200-1400 rpm. It will continue to do this until the car is warmed up. Once it's warm the car will idle steady around 900.
03-03-04, 12:12 PM
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mine is the opposite. when cold, if it idles at all, its at ~900, or it just dies. When its hot, it idles over 1500 and sometimes goes up and down between 1400-1750. For how long is the car cold during driving? Not often. you should be ok.
oh yeah, clean your BAC
oh yeah, clean your BAC
03-03-04, 12:18 PM
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We've been chasing this deamon for months now... First the AFM went bad. Then the TPS. Both were replaced. We then had the intake apart and replaced all of the rubber lines and gaskets. What a dirty job!
The BAC was washed with carb cleaner and we checked it with an electrical meter. It was ok.
I don't know what else to check.
The BAC was washed with carb cleaner and we checked it with an electrical meter. It was ok.
I don't know what else to check.
03-03-04, 12:31 PM
#4
TPS is a little out of adjustment.
BTW, it is pretty hard to get these cars to idle what most people could call "good". Generally you set them up in such a way that they idle okay when warm, and whatever they do when still cold is just what they do...since the car doesnt stay cold very long anyway.
BUt what I tell people, especially those with 89-91 nonturbo engines, is that it isn't ever gonna idle like your average new toyota camry...
BTW, it is pretty hard to get these cars to idle what most people could call "good". Generally you set them up in such a way that they idle okay when warm, and whatever they do when still cold is just what they do...since the car doesnt stay cold very long anyway.
BUt what I tell people, especially those with 89-91 nonturbo engines, is that it isn't ever gonna idle like your average new toyota camry...
03-03-04, 12:33 PM
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89GTUs, I have the same problem with my old car (which now belongs to my brother). I replaced all vac. lines a few weeks ago when cleaning the 5/6 ports. We have not replaced the tps b/c when tested it seemed ok. I found where I can get them cheap so I think we are going to replace it anyway. My next step is to take the throttle body off and adjust everything to within FSM specs (throttle plates, cold start, dash pot, etc.). I also cleaned the bac and as much of the ACV valve that I could get to (it had a decent amount of carbon buildup on it) to no avail.
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03-03-04, 01:01 PM
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Originally posted by RotaryResurrection
TPS is a little out of adjustment.
BTW, it is pretty hard to get these cars to idle what most people could call "good". Generally you set them up in such a way that they idle okay when warm, and whatever they do when still cold is just what they do...since the car doesnt stay cold very long anyway.
BUt what I tell people, especially those with 89-91 nonturbo engines, is that it isn't ever gonna idle like your average new toyota camry...
TPS is a little out of adjustment.
BTW, it is pretty hard to get these cars to idle what most people could call "good". Generally you set them up in such a way that they idle okay when warm, and whatever they do when still cold is just what they do...since the car doesnt stay cold very long anyway.
BUt what I tell people, especially those with 89-91 nonturbo engines, is that it isn't ever gonna idle like your average new toyota camry...
Hummm. We'll the car never had an idle problem till this winter when we replaced all the rubber lines and cleaned everything. I guess we should have left it alone.
The TPS has been adjusted twice now. Both times using a meter and setting it to 1 kohm. It's gotten better but not the way it was.
So is there a checklist that can be used for setting a good solid idle? Where do you start if you want to get it 100% again? I guess what I'm looking for is a step-by-step guide for idle adjustments. I've very good at following instructions.
03-03-04, 01:05 PM
#9
You are settting the TPS wrong. The FSM does not mention *settting* the TPS to 1kohm. The 1kohm is a range check, if you notice it says 1kohm +/- .5kohm. That means *once it is already set* you go back and check the range value, and it should fall within that area.
To set it, make a checker light from 2 LED's. Plug it in to the check terminal by the air box (green, 3 prong), turn the key on, and adjust the tps (engine warmed up fully) until one light comes on, one light stays off. This is the *setting procedure* per the FSM. *THEN* go back and check with the ohm meter to see that the value falls within .5kohm and 1.5kohm.
To set it, make a checker light from 2 LED's. Plug it in to the check terminal by the air box (green, 3 prong), turn the key on, and adjust the tps (engine warmed up fully) until one light comes on, one light stays off. This is the *setting procedure* per the FSM. *THEN* go back and check with the ohm meter to see that the value falls within .5kohm and 1.5kohm.
03-03-04, 01:10 PM
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Oops! We'll check that tonight.
The only weird thing is that we tried the 2 LED's before. When I plug them in and turn the key, they both flash on for a tiny second. Then I can't get them to come back on again. I can here clicking noises when I move the throttle, but the lights don't come on. Is something wrong with the wiring or computer?
We bought 12V LED's and I know they work.
The only weird thing is that we tried the 2 LED's before. When I plug them in and turn the key, they both flash on for a tiny second. Then I can't get them to come back on again. I can here clicking noises when I move the throttle, but the lights don't come on. Is something wrong with the wiring or computer?
We bought 12V LED's and I know they work.
03-03-04, 01:17 PM
#11
Every once in a while I get a car that will not operate the test lights properly. In this case I just adjust the TPS by ear, in a range pretty close to stock. (you usually have one or 2 threads showing under the lock nut on the bottom of the screw when it's close to being set). Then start the car cold and play with the setting (within reason) until it doesnt bounce, then watch what it does as it warms up. After you've adjusted it this way go for a drive to be sure it is still okay at low rpm transitions.
Everything on these cars is not by the book...things are old and resistances have changed greatly. IT is usually not possible to get one back to 100% perfect after it has been messed with...there are very few that are there even before being messed with.
Everything on these cars is not by the book...things are old and resistances have changed greatly. IT is usually not possible to get one back to 100% perfect after it has been messed with...there are very few that are there even before being messed with.
03-03-04, 01:21 PM
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Thanks for the help. I'll report back tomorrow how it goes. Gotta get to class now. *ugh*
PS: I would still love to see a step by step instruction for idle adjustments. There are just to many threads on here that bounce around the issue.
PS: I would still love to see a step by step instruction for idle adjustments. There are just to many threads on here that bounce around the issue.
03-03-04, 01:24 PM
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NEVER try to set the tps unless the engine is HOT. The tps is linked to the thermowax. The thermowax needs to fully extend prior to setting the tps. IF you set the tps while the engine is not fully warmed up (hot), then you will have wasted your time and effort
The above is for a NORMAL car with the throttle body fully in tact.
The above is for a NORMAL car with the throttle body fully in tact.
03-03-04, 10:03 PM
#14
Hailers is correct in that if you are setting one by the book, the engine must be warm. But, what I was describing works for some cars where settting by the book doesn't work out.
And gtuslady, what you're after is the factory service manual, mazda's own how-to book that dealer service techs used. Please go download it at www.fc3s.org how-to-->manuals-->89-91 FSM.
Between what we have told you here and what the FSM tells you, you have all the information you need.
But I am telling you, in my experience of hundreds of FC's that it is often hard or impossible to obtain a perfectly idling/running car when setting by the book...there are too many variables on the car that have changed with time, heat, and adjustment. Those adjustments worked perfectly when new, but don't always do so now. You *have* to take this into account, which is why sometimes you wind up playing it by ear.
And gtuslady, what you're after is the factory service manual, mazda's own how-to book that dealer service techs used. Please go download it at www.fc3s.org how-to-->manuals-->89-91 FSM.
Between what we have told you here and what the FSM tells you, you have all the information you need.
But I am telling you, in my experience of hundreds of FC's that it is often hard or impossible to obtain a perfectly idling/running car when setting by the book...there are too many variables on the car that have changed with time, heat, and adjustment. Those adjustments worked perfectly when new, but don't always do so now. You *have* to take this into account, which is why sometimes you wind up playing it by ear.
03-03-04, 11:26 PM
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Ah idle issues....welcome to the club...its called the rx-7 club 
But ya...check your tps and everything else everyone before me here has mentioned. I dunno if this has been mentioned as well...but look for vac leaks cuz that'll mess up your idle too. I changed my tps and readjusted it till the cows came home and it still surges when its cold. But whatever, she runs, im just happy about that
But ya...check your tps and everything else everyone before me here has mentioned. I dunno if this has been mentioned as well...but look for vac leaks cuz that'll mess up your idle too. I changed my tps and readjusted it till the cows came home and it still surges when its cold. But whatever, she runs, im just happy about that
03-04-04, 10:55 AM
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Wow! I guess I'm not alone in my funky idle. I recently bought a beautiful stock 90 blaze red convertible with 109k through ebay. The exterior is in fantastic shape and the interior is in very good shape. I have got more compliments and stares with this car then anything else! The car runs great and fires right up, BUT the idle is odd at times. Sometimes the idle hangs at 1k while in neutral at a stop light, but it will then drop to the proper 700 when you put the car in gear with the clutch pushed in. Sometimes it idles perfectly fine at 700 while in neutral. Sometimes the idle stays at 1500 even after the temp gauge reads halfway, but it generally only stays there for a short time.
However, the problem I'm most concerned with is this: when running the AC, sometimes the idle just dives right down to about 200 or so. Sometimes it catches itself and sometimes it stalls. What will fix this issue? Also, on a few occassions, with the clutch pushed in and the shifter in gear,the idle wildly fluctuated between like 1200-1500 roms in quick succession. Taking it out of gear made the fluctuation stop. What causes this weird phenomenon?
Is it a bad idea to use fuel system cleaners in a rotary engine? Any and all input is much appreciated.
However, the problem I'm most concerned with is this: when running the AC, sometimes the idle just dives right down to about 200 or so. Sometimes it catches itself and sometimes it stalls. What will fix this issue? Also, on a few occassions, with the clutch pushed in and the shifter in gear,the idle wildly fluctuated between like 1200-1500 roms in quick succession. Taking it out of gear made the fluctuation stop. What causes this weird phenomenon?
Is it a bad idea to use fuel system cleaners in a rotary engine? Any and all input is much appreciated.
03-04-04, 11:31 AM
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If the idle was good before you started replacing things around, then you most likely have created a small vacuum leak.
I would look for a vacuum leak first then adjust idle + tps according to the FSM.
I myself adjust the TPS so that the ECU sees 1.0 Volt.
I don't think it matters that much whether you have .95 or 1.05 V.
About the 2 light method, make sure you plug them at the right connector (not the one that checks for engine codes ... I am sure you've got the right one but I've seen that confusion before)
Hugues -
I would look for a vacuum leak first then adjust idle + tps according to the FSM.
I myself adjust the TPS so that the ECU sees 1.0 Volt.
I don't think it matters that much whether you have .95 or 1.05 V.
About the 2 light method, make sure you plug them at the right connector (not the one that checks for engine codes ... I am sure you've got the right one but I've seen that confusion before)
Hugues -
03-04-04, 02:32 PM
#18
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Originally posted by 90RX7convertible
However, the problem I'm most concerned with is this: when running the AC, sometimes the idle just dives right down to about 200 or so. Sometimes it catches itself and sometimes it stalls. What will fix this issue? *SNIP*
However, the problem I'm most concerned with is this: when running the AC, sometimes the idle just dives right down to about 200 or so. Sometimes it catches itself and sometimes it stalls. What will fix this issue? *SNIP*
I'm going to repeat what Hugues has said: Vacuum Leaks. The rubber lines crack and cause lots of little leaks giving you a funky idle.
The thing with the A/C has to do with the BAC Valve. When the turn on the A/C, the engine opens the BAC to raise the idle. If the BAC isn't opening properly, then your car will sometime stall. Clean the BAC with carb cleaner and check the resistance with an ohm meter. It should read something like 12-12.5 k ohm.
03-04-04, 02:53 PM
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What wozzoom said about AC and the BAC valve.
In addition, you may want to make sure the ECU is sending the proper signal to the BAC when the AC compressor kicks in.
I am not sure about the S5 but on the S4, if you monitor the DC voltage at the BAC or at the corrsponding ECU pin (it's a pulse so you can use DC voltage which will be an average of the pulse AC voltage), it should go DOWN when the AC compressor kicks in. This means the BAC is pulsing more and thus the ECU wants the idle to raise to compensate.
If the voltage does not change, you could have an ECU problem or the AC switch has a problem or there is a snafu in the wiring between those guys. If it goes down, at least you will have proven to the rx7 forum that your ecu works and that the BAC is probably the culprit.
agains, this behavior for S4, but S5 should be same.
You should look into S5 FSM which is much better than the s4 one. See sureshot's sig for download.
Hugues -
In addition, you may want to make sure the ECU is sending the proper signal to the BAC when the AC compressor kicks in.
I am not sure about the S5 but on the S4, if you monitor the DC voltage at the BAC or at the corrsponding ECU pin (it's a pulse so you can use DC voltage which will be an average of the pulse AC voltage), it should go DOWN when the AC compressor kicks in. This means the BAC is pulsing more and thus the ECU wants the idle to raise to compensate.
If the voltage does not change, you could have an ECU problem or the AC switch has a problem or there is a snafu in the wiring between those guys. If it goes down, at least you will have proven to the rx7 forum that your ecu works and that the BAC is probably the culprit.
agains, this behavior for S4, but S5 should be same.
You should look into S5 FSM which is much better than the s4 one. See sureshot's sig for download.
Hugues -
03-04-04, 06:21 PM
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Originally posted by RotaryResurrection
TPS is a little out of adjustment.
BTW, it is pretty hard to get these cars to idle what most people could call "good". Generally you set them up in such a way that they idle okay when warm, and whatever they do when still cold is just what they do...since the car doesnt stay cold very long anyway.
BUt what I tell people, especially those with 89-91 nonturbo engines, is that it isn't ever gonna idle like your average new toyota camry...
TPS is a little out of adjustment.
BTW, it is pretty hard to get these cars to idle what most people could call "good". Generally you set them up in such a way that they idle okay when warm, and whatever they do when still cold is just what they do...since the car doesnt stay cold very long anyway.
BUt what I tell people, especially those with 89-91 nonturbo engines, is that it isn't ever gonna idle like your average new toyota camry...
I went home last night and adjusted the TPS. Before I set it using the ohm meter method. This time I used the LEDs. I ended up taking about 2 full turns out of the TPS screw before the one light went out. I let the engine cool and now its perfect! I'm so happy.
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