3 Questions for Adrian about a C4
05-13-2003, 12:22 AM
#1
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3 Questions for Adrian about a C4
1) The light on my center console at the differential lock switch (small round yellow light) comes on intermittently when I go over a railroad crossing, speed bump or similar "rough" spot in the road. I think its electrical but where (literally) do I start my search?
2) After relatively hard breaking, my clutch will hang slightly and fail to return all the way...comes to within 1 inch or so of totally returning...only happens immediately after hard breaking...I know both are run from the hydraulic system but what is this symptom trying to tell me??
3) Can the knock sensor functionality be turned off in the DME? I remember seeing references to various switches for different country code versions of the DME. I have a US DME (version 03 on my 92 C4 - non California car) and would like to be able to turn of the knock sensors for troubleshooting purposes...I'm getting a knock sensor failure code that I cant clear out and want to see if there is any noticeable performance difference if the knock sensing function turned off in the DME...if the DME is retarding the ignition by 6 degrees, it should be a noticeable improvement. I've had the fault code since I got the car so I don't have anything to compare it to.
Thanks for your help and looking forward to you book hitting the stands.
Thanks!!
2) After relatively hard breaking, my clutch will hang slightly and fail to return all the way...comes to within 1 inch or so of totally returning...only happens immediately after hard breaking...I know both are run from the hydraulic system but what is this symptom trying to tell me??
3) Can the knock sensor functionality be turned off in the DME? I remember seeing references to various switches for different country code versions of the DME. I have a US DME (version 03 on my 92 C4 - non California car) and would like to be able to turn of the knock sensors for troubleshooting purposes...I'm getting a knock sensor failure code that I cant clear out and want to see if there is any noticeable performance difference if the knock sensing function turned off in the DME...if the DME is retarding the ignition by 6 degrees, it should be a noticeable improvement. I've had the fault code since I got the car so I don't have anything to compare it to.
Thanks for your help and looking forward to you book hitting the stands.
Thanks!!
05-13-2003, 03:34 AM
#2
Hi,
I can answer 1), and comment on 2).
1) This is basically just your traction control activating. Not surprising if you've gone over a bumpy surface like a railway crossing because your wheels will probably briefly leave the ground and hence will seem to spin as far as the computer is concerned. Doesn't sound like anything to worry about, system is working normally.
2) At last - someone has the same problem I do! Hanging clutch is quite a common problem, and most people fix it by replacing the slave cylinder. But I have also noticed that mine only does it after hard braking - but nobody can explain why. The only part of the system the brakes share with the clutch is the fluid reservoir (and I think even that is partially divided). I've asked my mechanic and people on here, and nobody can explain how heavy braking can cause this. My mechanic thought it might actually be the pedal assembly not the hydraulics but there was no problem there.
3) Can't answer that one.
I can answer 1), and comment on 2).
1) This is basically just your traction control activating. Not surprising if you've gone over a bumpy surface like a railway crossing because your wheels will probably briefly leave the ground and hence will seem to spin as far as the computer is concerned. Doesn't sound like anything to worry about, system is working normally.
2) At last - someone has the same problem I do! Hanging clutch is quite a common problem, and most people fix it by replacing the slave cylinder. But I have also noticed that mine only does it after hard braking - but nobody can explain why. The only part of the system the brakes share with the clutch is the fluid reservoir (and I think even that is partially divided). I've asked my mechanic and people on here, and nobody can explain how heavy braking can cause this. My mechanic thought it might actually be the pedal assembly not the hydraulics but there was no problem there.
3) Can't answer that one.
05-13-2003, 04:13 AM
#3
Burning Brakes
1. I'm amazed at the C4 drivers that can see this flashing light. I know mine flashes too but I never see it. I try to look where I'm going....!
2. I'm with the Pedal assembly theory on the clutch - mine does too and I've been meaning to strip and clean the linkage behind the pedal for just over two years but there never seems to be time.
3. as Homer wisely said "Doh!" I'm not in favor of messing with my DME's mind. Have you checked the sensors?
P.S. great colour - is your interior grey as well?
2. I'm with the Pedal assembly theory on the clutch - mine does too and I've been meaning to strip and clean the linkage behind the pedal for just over two years but there never seems to be time.
3. as Homer wisely said "Doh!" I'm not in favor of messing with my DME's mind. Have you checked the sensors?
P.S. great colour - is your interior grey as well?
05-13-2003, 04:37 AM
#4
Three Wheelin'
</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica">Originally posted by Irishdriver:
<strong>1. I'm amazed at the C4 drivers that can see this flashing light. I know mine flashes too but I never see it. I try to look where I'm going....!
?</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">At night on twisty roads it's a great 'you're getting close to the limit' indicator!
BR
Piers
1990 C4 Coupe
59K Miles
<strong>1. I'm amazed at the C4 drivers that can see this flashing light. I know mine flashes too but I never see it. I try to look where I'm going....!
?</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">At night on twisty roads it's a great 'you're getting close to the limit' indicator!
BR
Piers
1990 C4 Coupe
59K Miles
05-14-2003, 05:01 PM
#6
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Dear Chris,
Your questions have been answered. I can only add a couple of points. The yellow led is supposed to flash everytime the rear differential lock is activated. So this is telling you it is working. The light you do not want to see flashing on is the red PDAS warn.
The clutch can be many things. When did you last change your fluid. In a C4 you are supposed to change the entire system fluid every 2 years. Are you sure the fluid is not boiling.
For the knock sensors you cannot disconnect the knock sensors from the DME. The control circuit is inside the dme. You would have to find the chip sets and unsolder them and remove them. Not a recommended thing to do.
I really cannot think of anythign else you can do apaprt from borrowing a DME that does not have the fault recorded. Either that or replace the knock sensors. Are you reading this code with a check engine light or Bosch Hammer.
You can check the knock sensors are working. You need to gain access to the sensors. Start the engine and using a timing light line up the timing marks. Lightly tap each sensor and see if the timing marks move apart and when you stop tapping that they move together again.
Now just one other thing. I have also posted this before. If your knock sensors are actually working and are detecting a knock in three cylinders on one side they will actually fail and retard timing by 6 degrees. I doubt this is your problem though.
Please confirm if the fault code is being read by a hammer or check engine light.
Ciao,
Adrian
911C4
PS: If this is urgent please email me. I am usually 24 hour behind on the forum.
Your questions have been answered. I can only add a couple of points. The yellow led is supposed to flash everytime the rear differential lock is activated. So this is telling you it is working. The light you do not want to see flashing on is the red PDAS warn.
The clutch can be many things. When did you last change your fluid. In a C4 you are supposed to change the entire system fluid every 2 years. Are you sure the fluid is not boiling.
For the knock sensors you cannot disconnect the knock sensors from the DME. The control circuit is inside the dme. You would have to find the chip sets and unsolder them and remove them. Not a recommended thing to do.
I really cannot think of anythign else you can do apaprt from borrowing a DME that does not have the fault recorded. Either that or replace the knock sensors. Are you reading this code with a check engine light or Bosch Hammer.
You can check the knock sensors are working. You need to gain access to the sensors. Start the engine and using a timing light line up the timing marks. Lightly tap each sensor and see if the timing marks move apart and when you stop tapping that they move together again.
Now just one other thing. I have also posted this before. If your knock sensors are actually working and are detecting a knock in three cylinders on one side they will actually fail and retard timing by 6 degrees. I doubt this is your problem though.
Please confirm if the fault code is being read by a hammer or check engine light.
Ciao,
Adrian
911C4
PS: If this is urgent please email me. I am usually 24 hour behind on the forum.
