Misfire saga... Measuring blocks
11-29-2006, 10:51 AM
#11
AudiWorld Senior Member
Re: Misfire saga... Measuring blocks
Absolutely swap the coil packs around and see if the code moves with it. The first time this happened to me - maybe a year and a half ago - new plugs cured it. This time the fault moved with the coil packs and it kept getting worse...more cylinders...Unusual, but my ECU went in the drink and caused all kinds of electrical havoc...including a bunch of semi cooked coils. At 20$ per coil (2000 or newer) I just replaced all 8. Finally it runs perfectly again. My point is, don't overthink it. Check plugs and coils first.
but my indie does...what should i ask him to look for?
11-29-2006, 03:31 PM
#15
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You need to follow up on the high voltage knock sensor-good that you have found
the cause of the missfire but you should also recheck after basic settings the dodgy knock sensor.
You likely have had two seperate issues.
The knock sensor is very important to the engines well being and if not a faulty wire it may be something mechanical loose in there.
good luck
try changeing around the knock sensors and see if the voltage follows the sensor
You likely have had two seperate issues.
The knock sensor is very important to the engines well being and if not a faulty wire it may be something mechanical loose in there.
good luck
try changeing around the knock sensors and see if the voltage follows the sensor
11-29-2006, 05:13 PM
#16
"try changing around the knock sensors"? Why? There are only two. Left 4 cylinders and right 4.
It still escapes me why a knock sensor would malfunction for only one of the four cylinders it monitors.
Tom
Tom
11-29-2006, 05:55 PM
#17
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No I agree- his miss was the coil pack but if he still has a high voltage on
the one knock sensor then by swapping them it will rule out any mechanical causes if the high voltage follows the sensor.
The Elsa suggests that the cause of a high voltage in a knock sensor is probably a bad wire but can also be loose mechanical parts in the engine.
If it was my car I would want to rule that well out.
I doubt that the sensor was causing a missfire but he picked it up looking at the measuring blocks trying to find the cause of the missfire.
The Elsa suggests that the cause of a high voltage in a knock sensor is probably a bad wire but can also be loose mechanical parts in the engine.
If it was my car I would want to rule that well out.
I doubt that the sensor was causing a missfire but he picked it up looking at the measuring blocks trying to find the cause of the missfire.
11-29-2006, 06:21 PM
#18
"Shut off cylinders which knock too much" is probably not in the software
Haven't seen such a drastic response documented anywhere in the service manual, and if it did exist, it would make more sense for the resulting code(s) to be knock related, not misfire codes.
And I'd be really surprised if the programmed response to any knock sensor input could involve retarding the timing so far that a misfire is detected but no knock control limit code is set.
Tom
And I'd be really surprised if the programmed response to any knock sensor input could involve retarding the timing so far that a misfire is detected but no knock control limit code is set.
Tom
11-29-2006, 06:45 PM
#19
Sure, reread the knock sensor for completeness if you like. But it can be trusted w/o swapping
because it has only one output, not one wire for each cylinder, which gives normal looking readings 3/4th of the time (when the other three cylinders fire).
Also I'd rather not advise moving the knock sensors in case somebody swaps them without the service manual, unaware of their specified tightening torque which matters to knock sensors.
Tom
Also I'd rather not advise moving the knock sensors in case somebody swaps them without the service manual, unaware of their specified tightening torque which matters to knock sensors.
Tom
11-29-2006, 07:57 PM
#20
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point taken-at least an elerctrica ltest of the wires is necassary
Hopefully any tech working on these cars will not do so without checking torque settings for such an important item.
I would very much like to confirm there is no loose or rattly components in the engine.
I would very much like to confirm there is no loose or rattly components in the engine.
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