Replaced Spark Plugs, now throwing code 1226 (knock sensor)??
 

As the title states, I swapped out my Bosch Platinum +2's for a new set, same part number and everything. This is on a 1995 M42 motor w/194k on it.

I started the car when the job was done to be sure I didn't screw everything up. It started and idled fine. Then, this morning when I started the car it felt like it was mis-firing. I decided not to chance it and didn't drive it to work.

Tonight after work I started it and drove it around. All seemed well. I decided to do the stomp test and see if I'd thrown any codes. I got back a "1226" which corresponds to knock sensor #2. It would make sense that the mis-firing I felt was actually knocking or pre-ignition.

My question to you all is this...has anyone ever developed a knock after replacing your spark plugs?? Seems odd to me. The old ones looked like they were in great shape (dry, somewhat light brown coloring, nothing remarkable). Is it possible that my intermittent knocking is due to my new spark plugs?? Or do you think the two are unrelated??

Thanks in advance,
Matt

What model and year?

Assuming E36, make sure you replaced the two ground straps on the coils. Check the plug torque. Double check all connections

1995 318is, M42

Confession -- I did NOT use a torque wrench to tighten my spark plugs when installing them. I have a beam-type wrench, but was concerned I would over-tighten them. So I decided to use the smaller socket-wrench and torque to feel.

Based on that, I wondered if it was possible that I under-torqued them (out of fear of stripping something) and maybe it was vibrating around enough that the knock sensor picked it up and cut back the timing causing it to run rough and throw the 1226 code.

So, I borrowed a "click" type torque wrench from a friend and re-did everything. Turns out that 18 ft-lbs was a TON more torque than I had applied "by feel" :o Everything is running fine now that they are in there tightly.

Thanks SmileWavy

Matt

When I last installed new plugs I put them in by hand tight method then hit them with the torque wrench. The spec Torque was a good bit more than I put by hand.

Also, I noticed that there was a point where the plug became hard to turn but it is below torque spec so you have to turn past that and it gets easier again. I assume the brand new plug gasket is crushing and deforming into place.