Knock Sensor Woes

So after searching and researching I decided to get a 97 540i, the check engine light was on, so I talked down the price a little more, prior to buying I noticed it was a knock sensor code which I had changed on a few different cars in the past so I figured it would be easy, which was not true, anyway heres the story.

I removed everything (intake manifold, fan, water pump, etc) and got to the 4 knock sensors (2 different connectors) and replaced them, I then replaced all the gaskets and put everything back, everything seemed great until I got onto the freeway, if I go above 70 for some reason both knock sensor codes get thrown, has anyone heard anything like this?

Codes are P0330 and P0325, both are brand new, prior to the change, any speed would throw the p0330 (above 1700ish RPM) now it seems to be speed sensitive.

Any help or hints are greatly appreciated, I am stumped, I want to get this car smogged so I can finally start driving it. (I drove the car 60 miles today, kept it under 70, no codes were thrown, I am going to attempt to smog it and see if all the monitors are clear)

Thanks in advanced!

There has been at least one report on another forum, where the sensors were not placed EXACTLY in the same position as the original ones (rotated out of position).

The other problem might be dirty or corroded connectors.

Originally Posted by edjack

There has been at least one report on another forum, where the sensors were not placed EXACTLY in the same position as the original ones (rotated out of position).

The other problem might be dirty or corroded connectors.

Thanks for the response, ill search more on the other forums, I have already searched a great deal on this forums and bimmerboard, along with looking through bmwtips to no avail yet.

I dont think the connectors will be the problem, i cleaned them quite well with a pipe cleaner, they were pretty clean to begin with, as far as the positioning, i have no idea.

The search continues.

Those sensors can't take a lot of tourqe when installing them--to much will ruin them---did you find a tq level for the install?

Good point! TIS says 20 N-m, or 14.7 ft-lbs.

we torqued it to 16 ft/lbs, I did it based on a chevy sensor, I dont know how much 1.3 ft/lbs would effect. Do you think this can be the issue?

Don't know--I read once somewhere that too much tq would set them off and retard timing--thats what they are there for--also when I did the ones in my 960 Volvo--I used a green type of loctite on the bolts--was made just for these suckers.

for future reference of other users. Got my car smogged yesterday and passed with flying colors (really couldn't believe how low of emissions it was) Also ran it hard for about 100 miles, restarted the car, no CEL, so it looks like its just a code that is thrown at high MPH.


Now for the fun

You never mentioned what octane fuel you use...are you using the BMW recommended 89 AKI or higher (for the 1997 M62)?

Originally Posted by QSilver7

You never mentioned what octane fuel you use...are you using the BMW recommended 89 AKI or higher (for the 1997 M62)?

i use 91 octane, not sure if that makes a huge difference (is 89 AKI = 89 octane) should I go to 89 octane?

No.

Torque values will not effect the sensors performance. A knock sensor is a piezo electric crystal that generates its own voltage when a certain frequency, that only detonation can produce, is felt. This is why the sensor does not pick up vibrations from the road, driveline, etc. It must be the right frequency. I would trace the wires to the DME and make sure they are connected on that end.