Expert: Roland Finston - 2/8/2012

Question
QUESTION: I just replaced the camshaft sensor on my 1999 300m. I removed all the bolts that hold down the upper plenum then I lifted it up an inch or so in the front. I put the new sensor in. I tightened all the bolts and started the car and it is making a knocking noise that gets louder as you step on the gas. What could this be?

ANSWER: Hi Scott,
Might you have put the sensor in off-angle or too deeply? It might have had a timing slot right below the sensor tip, on the cam shaft, so you could have put it in too far. Other than that I will have to see what else might be doing that and let you know if I find something. Did you retighten the bolts in a clockwise fashion starting from the middle bolt on the engine's left side, and next the center 2 on the right side, and the the outer two on the left side, and finally the outer two on the right side of the engine? The torque spec is 105 inch-pounds or about 9 foot-pounds.
Roland

---------- FOLLOW-UP ----------

QUESTION: I checked to see if the sensor was down too far and it was not. I loosened all the bolts and retorqued them as close as I could to per your instructions but there are more bolts on top than you described. Anything else you could come up with would be greatly appreciated.          Thanks,  Scott

Answer
Hi Scott,
You may want to remove the upper plenum entirely and then reinstall it. It is not clear to me what might be the problem, but the manual does suggest removal entirely rather that the simple bolt loosening approach when changing the cam sensor. I only have '04 manuals on CD that I can copy from, but if you would like that procedure send me a new question, where you also check the box to make it private, and in the question text area tell me what your email address is. If you don't make it private then it will be erased. I don't see your email address routinely when you ask a question so you have to tell me.
Roland