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Idle screw gap (photo inside). How can I fix this?
Hi all. My car is a 91' S5 turbo FC convertible. The UIM was removed a few months ago in order to replace the injectors. Since then I have been reading the forum for many hours in order to find out how to properly adjust my TPS and idle rpm. There are 3 or 4 screws involved, hot and cold engine temperatures the dashpot and of course the TPS.
I have managed to adjust the TPS to 1 Kohm but the car still has some issues. At this point, as I am still troubleshooting, I would like to ask how to eliminate the "Bad Gap" that is shown in the photo. Also I would like to know what the other screw (labeled screw) does and If I have to turn it somehow in order to improve my idle. Thanks in advance for your help.
Was that "bad gap" picture taken with a cold engine? If it was, it might not be so bad -- Some gap there is what you would see with a stock, unmolested throttle body on a cold engine. With the engine at operating temperature, there would be no gap (throttle crank lever would be resting against the throttle stop/base idle position screw). If you screwed around with ANY of the TB screws (other than the one used to adjust the TPS), it's quite likely that whatever gap you're seeing is jacked up though, so you're going to need to get very familiar with the FSM and understand what all those screws on the TB do, and how to properly adjust them.
Thank you for your answer.
The photo is taken from another topic. My case is like this one but the gap is smaller. About 1/3 or 1/4 of the gap that is shown in the photo when its cold, and a little smaller when its hot.
The only screw that I turned is the one that is labeled Screw in the photo and when I turned it the car was at normal temperature (middle reading of the gauge). I did that in order to lower the idle rpm (it was around 1200 at normal temp) and I managed to have a steady 800 rpm idle. After that I readjusted the narrow range of the TPS at 1Kohm with a multimeter just like the FSM describes.
I have also unplugged the BAC valve and bypassed the cooling fluid line but the valve is still on the intake.
Is that bad? Should I remove it completely and block off the hole?
I read at another topic that there are also two more screws. that adjust the position of the throttle plates and there is also the dashpot.
Should I try to adjust the dashpot now or after the adjustment of the throttle plates?
Any suggestions?
better for what? what are you trying to accomplish?
Thermowax =/= BAC, btw
you are right, I forgot to mention that I am trying to lower my idle when hot. The car maintains 1500 rpm when I press the clutch to a stop before 1000 rpm. If I brake and press the clutch under 1000 rpm the idle sits fine at 900 rpm. But the car also jerks when I brake and the rpms are near 1200-1000.
what do you mean by the =/=? Thermowax and BAC are not related?
I turned the screw that is shown in the photo and managed to get a proper idle when the engine is at normal temperature.
But the gap is still there. Is this causing any problems? I live in area that there are no rotary experts at all. The closest one is 220km away.
I read the FSM again and again and also many posts in here but I can't understand how all these screws work and affect each other.
Is the throttle resting on the TPS sensor and not on that set screw? By that, I mean is the TPS adjusted so much that the throttle cannot close anymore?
Yes, I mean that there is a gap between the upper screw (bad gap) that is shown in the photo and the rest of the throttle mechanism, so I suppose that the TPS holds the throttle.
I just read in another topic that I should: "close the throttle plates via the throttle stop screw and then turn it open 1/2 a turn." and then "Adjust the TPS to 1v only after the above has been done.".
But I cannot turn the throttle stop screw as I said because its already screwed all the way and still cannot push the throttle anymore.
Also I read that in order to adjust the TPS I should ground the initial set jumper (the green one, single pin next to the leading coil). But the FSM does not mention anything like that.
This will likely be where your sputtering from your other post is coming from. You are trying to do 2 procedures at once here.
First is the gap. There's only 3 things that can hold your throttle open. 1. The throttle cable is too tight. 2. The Fast Idle Cam (FSM page F2-35) is holding it slightly open until the engine is warmed up (if you blocked off this coolant line, it will keep the throttle open). 3. If the other two are not the cause, the throttle position sensor screw could be so far out of adjustment that the throttle is resting on the sensor. Check and see what is mechanically holding the thing open first.
At this point, it's safe to say your throttle body and sensors are out of adjustment. The following recommendations will assume you are starting from the beginning
Procedure 1. Setting the throttle position sensors FSM F2-81. . What you are trying to do here is set the position of the throttle position sensors so that the ECU can register the position of the primary throttle plate as being at idle. If you have already changed the throttle set screw in your first picture (the bad gap screw), this will most likely be out of adjustment. You are not going to set your idle immediately. That will come later. As you're reading the FSM, you'll note that before you adjust your throttle position sensors, it wants you to warm up the engine. This will (if it's still hooked up) move the Fast Idle Cam away from the primary throttle shaft, so it will take care of situation 2 I listed earlier. Also listed in the FSM, you want to use a test lamp to set your TPS Sensors. You can easily make one of these by taking 2x 12v lamps and wiring them so that the two parallel pins are separate positives, and they share a common ground (see photo).
How to set your throttle body and TPS from scratch. We are assuming both throttle body, and TPS are out of adjustment.
-First we have to prevent the computer from compensating idle while you are making adjustments
-Screw BAC Idle Air Adjust screw all the way clockwise to close off additional airflow
-Ground green set connector
-Plug in checker lamp - this method will follow the FSM method for setting TPS. The resistance measurement stuff is for fine tuning. Right now, you want to make sure that the TPS are communicating with the ECU correctly.
-Warm up engine so that Fast Idle is out of the way.
-Check that primary throttle is against the throttle set screw.
-Check idle speed. It should be low, approximately 400-500rpm. This idle speed should barely be enough to keep the engine running. You are not trying to get it to idle at 750. That will be the computer's job.
-If idle speed is low as listed above, throttle set screw is adjusted correctly.
-If idle speed is high, reduce idle via throttle set screw until engine starts to die, and then increase slightly.
-Once throttle screw is set, turn off engine, set ignition to run position.
-Check lamps. Adjust TPS screw until only one lamp illuminates
-Turn ignition off and back to run. Ensure that lamps stay with only one illuminated to verify consistency.
-Start and stop engine and verify consistency again.
-If it doesn't stay consistent, let me know.
At this point, your throttle body and TPS sensors should be correctly adjusted.
Setting idle
With the throttle body and TPS properly adjusted, setting idle is easy.
-Ensure green jumper is grounded
-Start engine. It should still be running at approximately 400-500rpm from the previous step.
-Unscrew BAC Idle Air Adjustment screw until engine idles at 750rpm
-Turn off engine, disconnect ground wire, plug BAC back in if you disconnected it.
Idle is properly adjusted, and the computer should take over idle control.
I have attached pictures of the different parts of the throttle body I am talking about, as well as the BAC Idle adjustment screw. Let us know if you have questions or problems. Watch out for the belts when you have the engine running.
BAC solenoid with Idle Air Adjustment Screw Checker Lamp with 2x 12v lamps and common ground Fast idle assembly and throttle set screw Throttle Set Screw TPS Adjustment Screw
This will likely be where your sputtering from your other post is coming from. You are trying to do 2 procedures at once here.
First is the gap. There's only 3 things that can hold your throttle open. 1. The throttle cable is too tight. 2. The Fast Idle Cam (FSM page F2-35) is holding it slightly open until the engine is warmed up (if you blocked off this coolant line, it will keep the throttle open). 3. If the other two are not the cause, the throttle position sensor screw could be so far out of adjustment that the throttle is resting on the sensor. Check and see what is mechanically holding the thing open first.
At this point, it's safe to say your throttle body and sensors are out of adjustment. The following recommendations will assume you are starting from the beginning
Procedure 1. Setting the throttle position sensors FSM F2-81. . What you are trying to do here is set the position of the throttle position sensors so that the ECU can register the position of the primary throttle plate as being at idle. If you have already changed the throttle set screw in your first picture (the bad gap screw), this will most likely be out of adjustment. You are not going to set your idle immediately. That will come later. As you're reading the FSM, you'll note that before you adjust your throttle position sensors, it wants you to warm up the engine. This will (if it's still hooked up) move the Fast Idle Cam away from the primary throttle shaft, so it will take care of situation 2 I listed earlier. Also listed in the FSM, you want to use a test lamp to set your TPS Sensors. You can easily make one of these by taking 2x 12v lamps and wiring them so that the two parallel pins are separate positives, and they share a common ground (see photo).
How to set your throttle body and TPS from scratch. We are assuming both throttle body, and TPS are out of adjustment.
-First we have to prevent the computer from compensating idle while you are making adjustments
-Screw BAC Idle Air Adjust screw all the way clockwise to close off additional airflow
-Ground green set connector
-Plug in checker lamp - this method will follow the FSM method for setting TPS. The resistance measurement stuff is for fine tuning. Right now, you want to make sure that the TPS are communicating with the ECU correctly.
-Warm up engine so that Fast Idle is out of the way.
-Check that primary throttle is against the throttle set screw.
-Check idle speed. It should be low, approximately 400-500rpm. This idle speed should barely be enough to keep the engine running. You are not trying to get it to idle at 750. That will be the computer's job.
-If idle speed is low as listed above, throttle set screw is adjusted correctly.
-If idle speed is high, reduce idle via throttle set screw until engine starts to die, and then increase slightly.
-Once throttle screw is set, turn off engine, set ignition to run position.
-Check lamps. Adjust TPS screw until only one lamp illuminates
-Turn ignition off and back to run. Ensure that lamps stay with only one illuminated to verify consistency.
-Start and stop engine and verify consistency again.
-If it doesn't stay consistent, let me know.
At this point, your throttle body and TPS sensors should be correctly adjusted.
Setting idle
With the throttle body and TPS properly adjusted, setting idle is easy.
-Ensure green jumper is grounded
-Start engine. It should still be running at approximately 400-500rpm from the previous step.
-Unscrew BAC Idle Air Adjustment screw until engine idles at 750rpm
-Turn off engine, disconnect ground wire, plug BAC back in if you disconnected it.
Idle is properly adjusted, and the computer should take over idle control.
I have attached pictures of the different parts of the throttle body I am talking about, as well as the BAC Idle adjustment screw. Let us know if you have questions or problems. Watch out for the belts when you have the engine running.
BAC solenoid with Idle Air Adjustment Screw Checker Lamp with 2x 12v lamps and common ground Fast idle assembly and throttle set screw Throttle Set Screw TPS Adjustment Screw
Dear Pro Fire man you are THE MAN! Thank you so much for this awesome post. This should definitely be a sticky! I will make a dual light checker and do all the things that you suggest. I will update here with photos as well.
Thank you gain for all your effort.
I read again and again the procedure that Pyroman describes and tomorrow I will try to check all these things and try to adjust everything.
Today I went for a ride and since it was a warm day the car got warm up quick. I decided to check the throttle stop screw gap after the car got stuck in traffic and the engine bay was hot.
The gap was minimized or eliminated because I think that the screw is touching to the throttle mechanism. But I am not 100% sure, there might be a really small gap. But my idle was perfect at 900 rpm.
Also the throttle cable is not tight at all. In fact there is some freeplay in main cable as well as the auto pilot cable.
At this point I just want to ask why my stop throttle screw is screwed on the opposite side than the one in Pyroman photo (post #1, mine - post #12 pyroman's set throttle screw).
Does this matter? I think that if I reverse the screw (like in Pyroman's photo) then the gap will be eliminated even when the engine is cold.
Ok thanks. Yesterday I reinstalled the BAC valve and checked again the gap. The gap is eliminated and the screw is touching the rest of the mechanism. So I try to check and adjust all the other things that you suggest.
I will update with photos probably tomorrow.
[QUOTE=erevos;12397573
Also the throttle cable is not tight at all. In fact there is some freeplay in main cable as well as the auto pilot cable.[/QUOTE]
there is supposed to be some freeplay, if not then the cable can hold the throttle open
Just a quick update...
As I said I reinstalled the BAC and now the car has a perfect steady idle at 900rpm. I also checked the TPS with the LED light checker that I made according to Pyroman's instructions.
As I turned the key to on position, a single light turned on, so my TPS is adjusted. I was sure for this because as I said earlier I had already adjusted it at 1kOhm with a digital multimeter.
There is no gap when the car is hot or cold, but now the engine needs 2 or 3 tries in order to start with a gear and the clutch pressed in order to eliminate the accelerated warm up system. If I don't do that then it needs more tries and some throttle press in order to start.
I recorded a video that shows that the fast idle assembly is not aligned with the roller when the car is hot. Is this normal?
Here is the video.
Another update...
Today I replaced the AFM with another used one. Now the idle speed is steady but only for 4-5 seconds and then it drops and the engine stops. I tried to turn the BAC screw all the way clockwise as Pyroman suggested. The engine could not hold a proper idle and then I started to turn the BAC crew in order to raise the idle rpm. I managed to have a steady 750 rpm but when I tried to drive the car, the idle was steady for 4-5 seconds and then it dropped and the engine stoped. I unpluged the BAC and then the idle was steady again at 800-900 rpm.
So I guess that my BAC is damaged, right?
I checked the TPS with the LED light method and only one light is on so I guess that my TPS is properly adjusted.
Is there any other way to check that my trottle plate position is correct? As you can see in the last video the fast idle roller is not aligned properly when the engine is hot. Is this a problem?
@professionalpyroman: definitly the best writeup on this topic for s5 so far!
@erevos: if you still have a gap when your engine is hot, try to lift up the linkage with the 'screw' with a screwdriver and verify, if the gap is closed. If so, you should need to adjust the screw because the fast idle assembly has to completely separate from the roller when hot!
@professionalpyroman: definitly the best writeup on this topic for s5 so far!
@erevos: if you still have a gap when your engine is hot, try to lift up the linkage with the 'screw' with a screwdriver and verify, if the gap is closed. If so, you should need to adjust the screw because the fast idle assembly has to completely separate from the roller when hot!
thanks for your reply. No the gap is gone when the car is hot.
02-24-20, 10:59 AM
