clutch switch high idle problem
02-09-06, 06:02 PM
#1
clutch switch high idle problem
i searched last night but never could find the answer. I had this pulsation problem and thru the troubleshooting found the upper pedal clutch switch was bad. I replaced it and got rid of a annoying pulsation issue but now idle is 1500rpm. I did this so far....
Keep in mind TPS is brand new set (1 light LED), timing ok, and did stethescope around connections for air leaks-no leaks
1. Unscrewed new switch from pedal and played with plunger w/engine running--no effect, high idle @ 1500.
2. Unplugged switch harness and idle went lower but back to the annoying pulsations
3. Ran codes-no codes
4. BAC seems to be ok
Not sure what to do now? I read some searches people had similar problems but no resolution was ever given. Anyone?
Keep in mind TPS is brand new set (1 light LED), timing ok, and did stethescope around connections for air leaks-no leaks
1. Unscrewed new switch from pedal and played with plunger w/engine running--no effect, high idle @ 1500.
2. Unplugged switch harness and idle went lower but back to the annoying pulsations
3. Ran codes-no codes
4. BAC seems to be ok
Not sure what to do now? I read some searches people had similar problems but no resolution was ever given. Anyone?
02-11-06, 12:52 AM
#4
HAILERS
Join Date: May 2001
Location: FORT WORTH, TEXAS,USA
Posts: 20,563
Likes: 0
Received 22 Likes
on
20 Posts
Page F2-35 and 36 of the online S5 FSM. Fast Idle Operation is the title. Rework the engine to the requirements of those pages.
When the thermowax piston moves, the throttle linkage moves. When the throttle linkage moves the TPS moves. That is why the engine has to be HOT when you set the tps. You set a tps with the Fast Idle Cam and the roller seperated. If you don't, then the tps is being set wrong.
If the cam and roller don't seperate, then the throttle plates are open more than they should be at idle with a fully hot engine. Make sense? Yes.
Just for your entertainment, you might put your meter on the tps narrow range output AT the ECU and monitor it sometime. When the engine is cold the reading might very well be in the 2vdc range, but as the engine warms up and the cam and roller gradually seperate, the voltage output of the tps narrow range will gradually come down to specs for a hot engine. That spec is approx 1vdc at idle with a warm/hot engine. See page F2-78 of the S5 online FSM.
The lower clutch switch input/output is given on page F2-77 at the bottom of the page. Put a meter on it and turn the key ON and see if the switch is doing what it is supposed to do with the pedal depressed/released.
Personally, I would watch the narrow range input to the ECU from a full cold engine to a full hot engine to see what is happening with the tps output. It should give you a clue as to what is happening with the thermowax. Thermowax are difficult to look at on a non turbo. At least that is what I remember about my non turbo car.
Just a lot of words saying I think the thermowax is sticking. Fix it.
When the thermowax piston moves, the throttle linkage moves. When the throttle linkage moves the TPS moves. That is why the engine has to be HOT when you set the tps. You set a tps with the Fast Idle Cam and the roller seperated. If you don't, then the tps is being set wrong.
If the cam and roller don't seperate, then the throttle plates are open more than they should be at idle with a fully hot engine. Make sense? Yes.
Just for your entertainment, you might put your meter on the tps narrow range output AT the ECU and monitor it sometime. When the engine is cold the reading might very well be in the 2vdc range, but as the engine warms up and the cam and roller gradually seperate, the voltage output of the tps narrow range will gradually come down to specs for a hot engine. That spec is approx 1vdc at idle with a warm/hot engine. See page F2-78 of the S5 online FSM.
The lower clutch switch input/output is given on page F2-77 at the bottom of the page. Put a meter on it and turn the key ON and see if the switch is doing what it is supposed to do with the pedal depressed/released.
Personally, I would watch the narrow range input to the ECU from a full cold engine to a full hot engine to see what is happening with the tps output. It should give you a clue as to what is happening with the thermowax. Thermowax are difficult to look at on a non turbo. At least that is what I remember about my non turbo car.
Just a lot of words saying I think the thermowax is sticking. Fix it.
02-11-06, 01:04 PM
#5
Thanks HAILERS. I was playing with it and used a mirror and saw the plunger come out as it heated up. For the life of me I couldn't see the cam. I had white out on the marks when I had the TB off last year, but could not see them. I even got under the vehicle but could not see. Guess I'll have to remove the TB once it cools.
For checking the clutch switch you mean upper switch, right. thats the one I changed.
Just seems wierd this occurs with the new upper clutch switch.
For checking the clutch switch you mean upper switch, right. thats the one I changed.
Just seems wierd this occurs with the new upper clutch switch.
02-11-06, 04:29 PM
#6
HAILERS
Join Date: May 2001
Location: FORT WORTH, TEXAS,USA
Posts: 20,563
Likes: 0
Received 22 Likes
on
20 Posts
Upper?????? Hmmm. ON my S4, I have a switch waaaaaay up on the top of the clutch pedal. That is the starter interlock switch and used only for making the start circuit from the ignition switch to the starter.
There is a lower switch. It is used for cruise control and also a signal to the ECU that the clutch is depressed.
The clutch switch waaaaay up on top can hardly be seen , but it's there. If you disconnect that one your car won't start because the starter circuit is disrupted.
Maybe S5 are different? got me. Never seen one.
There is a lower switch. It is used for cruise control and also a signal to the ECU that the clutch is depressed.
The clutch switch waaaaay up on top can hardly be seen , but it's there. If you disconnect that one your car won't start because the starter circuit is disrupted.
Maybe S5 are different? got me. Never seen one.
02-11-06, 05:37 PM
#7
Mine is an S5 and there are two clutch switches that Im aware of. One floor area and one on the upper clutch pedal. Its a PITA to get at. The upper switch has something to do with the AWS and BAC but I'm not clear on this (FSM F1-40 schematic). I knew it was bad when I did switch checks using the OEM code checker for switch operation.
Ran out of time today. Went to drop off old oil at Autozone and get the engine hot and when I left there it was working correctly for about 10 minutes then it went back to high idle. I plan to take off the TB tommorrow to check the cam is sticking.
Ran out of time today. Went to drop off old oil at Autozone and get the engine hot and when I left there it was working correctly for about 10 minutes then it went back to high idle. I plan to take off the TB tommorrow to check the cam is sticking.
Trending Topics
02-11-06, 10:24 PM
#8
HAILERS
Join Date: May 2001
Location: FORT WORTH, TEXAS,USA
Posts: 20,563
Likes: 0
Received 22 Likes
on
20 Posts
The lower switch should have a Yellow wire with a Blue stripe and a pure Black wire.
The upper switch is the Interlock switch and has a Black wire with a Green stripe and a Black wire with a Red stripe. This switch is for making a circuit for the starter solenoid from the ignition switch. It also supplies 12vdc to the Circuit Opening Relay coil to make the fuel pump run as long as the ignition key is to Start. It also supplies 12vdc to pin 1C on the ECU to let the ECU know that you are starting the engine so the ECU will use the START fuel map for starting instead of the afm for fuel during Starting.
The lower switch (not so low when you look at it, but lower than the Interlock switch), is used for killing cruise and also supplying a signal to the ECU to let the ECU know the clutch pedal is depressed and it then helps kill the AWS. That is the switch with the Yellow/Blue and pure Black wires.
Anyway, that's my take on the two switches. I looked at the S5 manual sections F1, G and the wiring diagrams.
Once and only once I had a 1000rpm plus idle. That one and only time I traced it to the bac. I took it off and poured carb cleaner in it over night and flushed it out in the morning. The 1000rpm plus went south after that. I think it must have been cracked open a touch more than it should have been or not returning to close. Got me. Once the rpm is over about 1000-1100 rpm, then the ECU all by itself will advance the timing and make the engine go even a few rpm higher.
There's a lot of angles to this high rpm at idle thing. Good luck.
The upper switch is the Interlock switch and has a Black wire with a Green stripe and a Black wire with a Red stripe. This switch is for making a circuit for the starter solenoid from the ignition switch. It also supplies 12vdc to the Circuit Opening Relay coil to make the fuel pump run as long as the ignition key is to Start. It also supplies 12vdc to pin 1C on the ECU to let the ECU know that you are starting the engine so the ECU will use the START fuel map for starting instead of the afm for fuel during Starting.
The lower switch (not so low when you look at it, but lower than the Interlock switch), is used for killing cruise and also supplying a signal to the ECU to let the ECU know the clutch pedal is depressed and it then helps kill the AWS. That is the switch with the Yellow/Blue and pure Black wires.
Anyway, that's my take on the two switches. I looked at the S5 manual sections F1, G and the wiring diagrams.
Once and only once I had a 1000rpm plus idle. That one and only time I traced it to the bac. I took it off and poured carb cleaner in it over night and flushed it out in the morning. The 1000rpm plus went south after that. I think it must have been cracked open a touch more than it should have been or not returning to close. Got me. Once the rpm is over about 1000-1100 rpm, then the ECU all by itself will advance the timing and make the engine go even a few rpm higher.
There's a lot of angles to this high rpm at idle thing. Good luck.
02-12-06, 04:46 PM
#9
You're right! its the lower. I could've swore and bet all the money it was higher but it wasnt. It is the yellow-blue and black wire switch. My bad
Its cold here 40s, so I decided to leave the TB removal for another day. But i did remove the BAC to clean it. I was shocked how dirty it got in just one year. I checked the Ohms on it and my spare and they were both 11.3 Ohms. Also put leads to the battey and ground and saw the plunger click and move on both. However, I connected the BAC connector and turned the ignition switch on and nothing happened! It should click right? I may have a wiring issue.
Its cold here 40s, so I decided to leave the TB removal for another day. But i did remove the BAC to clean it. I was shocked how dirty it got in just one year. I checked the Ohms on it and my spare and they were both 11.3 Ohms. Also put leads to the battey and ground and saw the plunger click and move on both. However, I connected the BAC connector and turned the ignition switch on and nothing happened! It should click right? I may have a wiring issue.
02-12-06, 05:31 PM
#10
HAILERS
Join Date: May 2001
Location: FORT WORTH, TEXAS,USA
Posts: 20,563
Likes: 0
Received 22 Likes
on
20 Posts
Pull the small wire of the starter solenoid, then turn the key to STart and hold it in Start. The bac should go wide open.
Or I'm puzzled why the bac did not humm when you put the key to ON. Try that again and if it does not humm then play with the throttle linkage to move the tps. I think it'll move then. I wonder if this is a temperature issue with it not humming? Get the engine temps over sixty and try that again.
Or I'm puzzled why the bac did not humm when you put the key to ON. Try that again and if it does not humm then play with the throttle linkage to move the tps. I think it'll move then. I wonder if this is a temperature issue with it not humming? Get the engine temps over sixty and try that again.
02-13-06, 04:26 AM
#11
I put the spare BAC and idle went into crazy pulsation rapidly cycling. I used the old gasket so I'll finish cleaning the other BAC and install with new gasket.
Yeah, I tried a coulple times with the key on and no movement of the BAC plunger. Off the vehicle with 12V there was movement . I didnt think of moving the tps. I'll try that if after work.
Yeah, I tried a coulple times with the key on and no movement of the BAC plunger. Off the vehicle with 12V there was movement . I didnt think of moving the tps. I'll try that if after work.
Thread
Thread Starter
Forum
Replies
Last Post
trickster
2nd Generation Specific (1986-1992)
25
07-01-23 04:40 PM
CaptainKRM
2nd Generation Specific (1986-1992)
14
08-26-15 09:52 PM
