Knock sensors

gtg737m · Post by **gtg737m** » 31 Mar 2006, 06:10

Hello everyone,
I have a 1994 Volvo 850 Turbo wagon and I changed the knock sensors myself 2 months ago. Yesterday my check engine light came and apparently I have a code for faulty knock sensors. I followed all the steps described in the Haynes book and a Volvo manual that I bought to change the knock sensors but I'm not sure if there is something unique that one has to do whenever the knock sensors are being installed. I have the car at the dealer right now and the mechanic ask me what torque did I applied when I was installing the know sensors since this is very critical in their installation. It sucks that I had to take the car to the dealer now that they charge big time to remove the intake manifold to check the knock sensors. Does anyone know of a way of checking if the knock sensors are good or bad? I'm asking this since I called yesterday the place where I bought the knock sensors and they told me that if the knock sensors were bad, any authorized Volvo dealer would need to replace them. The only thing that suck is that I would have to pay for hand labor since I did this job the first time myself. I appreciate any help that can be offered to figure out a solution for this problem. Thanks.

Post by **MadeInJapan** » 31 Mar 2006, 07:03

See my post in the 850/S/V70 section.

csbrianp · Post by **csbrianp** » 01 Apr 2006, 22:30

I just changed my knock sensors because I was getting a code of 1-4-3, knock sensor absent or faulty. I replaced them Wednesday, and today Saturday the code is back. My thought is the wiring must be faulty. I sprayed the connectors with contact cleaner, but...... The one nice thing about having the dealer install them, if they go out again in a few weeks (or days) the dealer should replace them again for free.
My check engine light doesn't come on, but I can only pull 7lbs of boost.

Brian

Post by **MadeInJapan** » 02 Apr 2006, 00:11

lack of boost sounds like something else completely to me. Check for broken vacuum hoses and elbows. Soft elbows and hardened rubber hoses to the consistency of plastic may also leak.

White850Turbo · Post by **White850Turbo** » 02 Apr 2006, 06:57

Could be in limp mode, thus limiting boost to help protect the engine b/c it thinks that there is excessive detonation in the chambers due to bad signals from the knock sensors.