O.K., I think I've isolated my problem down to the knock sensor. I saw in the archives that it should have a resistance of about 8 megohms. Mine is showing open but yet still seems to have some affect on the engine control.

Question: should the sensor have a measurable resistance and if so, what value?

thanks

This may or may not be conclusive but the car is running great with the new sensor. Since my original problem was intermittent, I'll have to give it a couple days before I break out the bubbly! I'll post results.

Thanks again to all

I don't see a previous post.

What is the trouble with your car?

Does it have codes for knock sensor?

What engine?

Hi Abe, I can't seem to find the original post either. I have an 89 760 turbo (B230ft)W/104K miles. The car has always (I bought it used W/73K miles) had problems with low power and recently has been missing violently on an intermittent basis. It has become more constant and seems to happen after a certain amount of time during my daily commute ( worse in the evening after sitting in the sun all day). I have recently replaced all the high voltage items. I just changed the power stage, fuel pres. reg., fuel filter and fuel check valve. I have checked all turbo hoses and inlet hoses for leaks and have cleaned the communtator on the idle control valve. I have also checked the vacuum lines.

Most resently, I have noticed that the car ran well after I had messed with the knock sensor (ie R+R, cleaned connector, different torque settings, etc). Yesterday, while test driving the car and it was severely crapping out, I removed the sensor to check the resistance. Noting an open circuit, I was scatching the pins with my VOM probes to insure contact even though the pins are very clean. As a result, I was tweaking the pins back and forth a bit. I seemed to be getting a reading from time to time after tweaking the pins. After awhile, I couldn't get anything but an open circuit. I replaced the sensor and the car ran great! As a matter of fact, It has never ran this well. Excellent power in and out of turbo. Much more like I expected. I'm currently thinking that an intermmitent failure in the knock sensor has been retarding my spark under normal conditions.

According to abe, the later knock sensors have a resistance ranging from 2 to 8 meg ohm. The earlier knock sensors are open circuit. He feels the resistance test is not reliable, and says the knock sensors rarely fail, except when overheated.

I would test the knock sensor by quickly bouncing a light hammer off the engine block near the sensor with the engine running. If you do this fast enough it should cause the engine rpm to reduce. The force needed is very light no more then driving a thumnail into a wall.

Bill D.

If the test is to be successfull, you need to be lucky enough time your hammer strike very near when the engine fires.