who know about knock sensors??

Does anybody know how sensative the knock sensor is suposed to be???

I don't have alot of expirience testing them so I am unsure of my findings.

The manual says to tap on the right exhaust manifols and watch the scanner for indication of knock.
The manual also says to tap near the sensor.

I get nothing rapping on the exhaust manifold with my pliers but when I rap on the block right beside the sensor; the scanner does not display yes for a knok but the timing does retard, and the scanner shows the knok retard in degrees.

When I rap right on the sensor it displays a knok most times.

I would have thought the sensor to be more sensative then that .

Can somebody with experience please comment. Do you think that is normal responce? I don't want to spend $100 on a sensor if I don't need one.

Thanks

M1D

Thanks Donivan

Not sure if mine is the same as the 2.8 or 3.1.

There are two posabilities for my 1988 305, the napa people say I have to go to the dealer with the vin number in order to know which is the right one.

Mine is suposed to be GM p/n 10456287

I have heard they come in different sensativitys, generally smaller engines = more sensative. You don't want one too sensative or it will be retarding the spark when it dosn't need to be.

I know the restr of the stark control system works. I don't get code 43 but I do here knocking from time to time. Especially if I have regular gas in her.

I have a programable chip for the ECM which will be set up on the dyno. Dyno time costs money so I want to make sure everything else is right before I get there.

a couple of questions here m1d, where did you mount the knock sensor
2 did you use thread tape on the threads?
3 is it the one that came with the engine?
there are a couple of different sensors for fi engines, they have
different resistance values, not sure if the mt 2500 will
tell you what yours should be. I have found that it takes a hammer
about the size of the ordinary claw hammer to get the knock
sensor to see a knock when knocking on the block.
are you having pinging problems? I have seen in the past
non functioning egr valves be the cause of this problem.
Might check to see if it will open with a hose to manifold
at an idle. If the engine does`nt stumble or die the valve is no good.

1. They are very sensitive to installed torque.
2. They are selected for the frequency they hear. As mentioned, smaller engines knock lighter than big engines (talking individual cylinders, not total displacement).

ANY sensor info you see from a scan tool has gone through the following trip
A. sensor input to PCM
B. PCM interpets sensor data.
C. PCM hexidecimal interpretation of input is used internally.
D. PCM also reports this info on communication circuit at high speed.
E. Scan tool asks for the info on a slow speed communication line from the ALDL.
F. The PCM interpets this request, then talks back to the scan tool over the slow speed line with it's hexidecimal output.
G. The scan tool decodes this info and dislpays the result. It is probably much slower than even the slow speed comm line.

All of this is to support the next thing I'd suggest: Connect a DVOM or even better a 'scope directly to the sensor to see what is happening. I'd still have the scan tool connected, so you can see the input and the reported results.
I've seen some scantools that are fast enough to be not noticable to humans (less than a 10th of a second), and I've seen some that are sorely lacking. The report and refresh rates on something as fast as a knock sensor can somethimes be skipped right over.

If you do a search for Knock sensor pattern in web and images, there is lots of info.

Thanks for all the imfo guys; I now no longer believe I have any ESC system issue. Thanks for your help with that.

I am getting knock but for other reason, the dyno test showed the fuel curve being too lean at lower rpm. Thats the main problem causing knock and the ESC system is doing its best to deal with it.

I have two other issuse I believe to be causing all this. I have removed the A.I.R. system which makes this engine run a little leaner but I also have leaking injectors which are causeing flooded start condition and the worst ones are right at the single 02 sensor location which might be causing a false too rich indication.

Anyways I pulling the intake right now, getting new injectors and then off to the dyno with my new programable chip set.

M1D

replacing your leaking injectors will get the lean knock cured for sure.

Yep, that is often the case; a computer is looked at for all the answers and blamed for all the problems, but you have to take care of the basics first!
Compression, Air, Fuel, Spark and Timing!
Glad to hear you've found a problem and are working toward a solution!