Picked up my '94 850

[misha]

What CVVT on '94?

[abscate]

Correct - its not a CVVT issue on a 1994. Whats important to understand is any poor running condition that causes modest knocking can trip a knock sensor code which is not a knock sensor failure. The sensors are not cheap, so they are costly parts to throw in.

[volvofornia]

So I just checked the voltage and resistance on the sensors during engine on disconnected from the wiring harness.

After I turned on the engine I got a voltage reading for both of them around 50 mV. While the engine headed up the voltage went down to around 6-8 mV. One strange thing was that one sensor gave me a strange reading. Starting from around 8 mV the voltage went down to 0 mV and switched polarity to around -7 mV stayed there for a few seconds and came back. I could see this behavior only on one sensor though.

I also checked resistance while the engine was idling and warmed up. I got a reading of 5.2 Ohm and 4.7 Ohm on the other side.

Really hard to interpret this kind of values. Is there any car specific (or knock sensor code specific) data sheet which gives me a hint how to interpret this?

Yes, I also see the point that the sensors dedect some strange engine noise. I also read that it could be the sensor directly which is faulty. Well, I might see somebody who has the right equipment to read the data while the code sets.

I also noticed that the engine was running pretty smooth while the knock sensors where disconnected.

[volvofornia]

The sensors are not cheap, so they are costly parts to throw in.

As far as I can see they are between 60 - 70 bucks.

http://www.ebay.com/ulk/itm/150765444483

[abscate]

The sensors are not cheap, so they are costly parts to throw in.

As far as I can see they are between 60 - 70 bucks.

http://www.ebay.com/ulk/itm/150765444483

In the Northeast, 5 bucks is an expensive part. Its a grad school thing. Ok, that was 30 years ago, but its still true. I filter my engine oil through TP stolen from work rather than use a used coffee filter from home. A good coffee filter lasts a week, after all.



You need an o-scope and a function generator to test a knock sensor - passive resistance measurements arent too useful. And you can't tap on the block and look for timing changes like your Dads Buick either,

[volvofornia]

Haha Abscate,

I totally get what you mean Not saying 70 bucks is nothing but well, what the car needs the car gets

Ok, I did another test. I disconnected the sensors completly and drove around. The first 5 minutes everything was fine (no CEL) until it showed up again. I checked the codes and I got P0326 and P0331. Means basically no signal from both of the sensors.

My conclusion is that sensor 1 is just not working proper cause I get the same code while disconnecting both of them. I know that it is kind of a generic code but I have to replace the sensors now to see if its working. I order that part now. Lets do it

[abscate]

I hope it fixes it. Its a terrible job on a turbo ETM car - you have to pull the IM to get at the sensors.

If it doesn't fix it, Im having a special deal on coffee filters this week

[volvofornia]

All right. Great news!

After changing the knock sensor the CEL cause of the P0326 code never came back. Today I also went to do the smog check again and passed with waving flags To celebrate we drove together to the Vasquez Rocks where we arrived save and sound. It was a great first ride. Thanks to everybody who was involved so far to make this happen. It's a great feeling to know that there are people out there who care and are willing to share their knowledge.

But the journey is not over now. Still need to finish stage 0. Next up: Brakes, Tires, Suspension...

[Sommerfeldt]

Great stuff. Also, that pic looks kind of like some of the old Volvo advertising shots for the 850s. It's excellent.

- S

[misha]

Great news
Now.....Enjoy your Volvo.