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Camshaft pos sensor output & coil failure (perhaps?)
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19-11-2023 10:19am#1
Hi, my A4 B6 1.6 developed a misfire on cylinder 2&3. It happens when the engine has warmed up and I have confirmed there is no spark, so an ignition issue rather than injector etc.
It has a coil pack rather than a coil on each plug.
I did a resistance check on the high tension side, getting 17k between the 2/3 and 1/4 leads, I was hoping to find 2/3 open, so if it's the coil, it's either on the low tension side, or a crack causing the failure. Problem is, the coil is at the back of the engine near the bulkhead and it's a big job to get to, or even change the leads. So, I want to make sure it's the problem before I change it.
To eliminate other components, I put a scope on the camshaft position sensor and am getting a nice stable square wave (while it was just running on 1&4). The crank sensor was replaced last year (unrelated) so I didn't bother looking at that.
The frequency of the square wave at idle, about 800rpm was about 6.5hz. So the camshaft was doing 400RPM, or 6.6 revs per second. So, 6.5hz would suggest the camshaft creates just one pulse per rev - I would have assumed it would be many more. Is this normal? Here is a pic of it, if the part I've circled is the sensor reluctor then it appears my sensor is OK.
Am I missing anything before I go to replace the coil?
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