Kanookstr

Is there a way of testing the knock sensor on a 1999 502 Mag MPI with the MEFI3 ECU without using a scanning tool????

I noticed a ping, Kinda like an Octain/detonation ping, on the starboard side of my motor only at cruising speed of around 3500 RPM.
It's not there below 3500 rpm.

It's not the gas. and when the pinging started it was like turning on a switch. I noticed it right away.....Fuel pressure was fine, EGT temps where fine, ????Motor is running and pulling as strong as it usually does.

Can I just unplug the Knock sensor, and it would put it in safe mode????? This way I can try running up to the 3500 rpms and see if it still pings??? or unpluging the knock sensor doesn't work that way????

Thanks

blown1500

Official GM test method, taught at GM school:
Use a hammer and punch or similar instrument, strike the engine on the head, manifold, or other solid spot. A good rap should cause the engine to momentarily loose rpm. If not, the sensor is not working.
A plug check is in order!!!

Kanookstr

I was hoping there was a way to test the system without the sensor. this way if it worked, I would know it's the sensor thats bad. She's pinging enough at 3500 RPM that I don't need a hammer or punch. (Kinda like going up hill in the pickup when you just filled it up with 87 octane gas..) I havn't opened her up sense I noticed it.
I wonder if I unplug it and then ground the sensor wire while under way. If I notice a difference then I now the system is working, and it's the sensor itself. If it doesn't make a difference, then it could be the ECU, broken wire, ect... but not neccesary the sensor itself. But I don't know if it works that way????

bobby daniels

OH the joys of fuel injection
those sensors go bad alot for corrision and you can do a test like you said but its not accurate all the time ,

Kanookstr

So grounding that wire will have an effect while under way bobby D.??? That would help determine if it's the sensor itself. Because like I said, after 5 hrs of use this year. the ping suddenly appeared??? and it wasn't after filling the tank or anything else.

Kanookstr

OK, Jumped in the boat this morning to look for a lose wire and check the plugs.
No lose wires, and all plugs looked great.?????
As I was putting in the last plug, my shirt sleeve got caught on the dip stick..... when I yanked it free......
PING<<>>TANG>><<PING.... went the dip stick TUBE!!!!
WHAT was that I thought????? I started shaking the tube and sure enough it sounded a Lot like that pinging I heard. So I followed the tube down to where the holder was, and sure enough it had a real shiny spot where it rapped around the tube.
I then started thinking how weird it was that the engine only pinged on the starboard side, and at exactly 3500 rpm. it didn't do it at 3700+ rpm, nor did it do it at a lower RPM. it also only did it when I was at that rpm cruising, not on acceleration like normal detonation would ac-cure...
Lets just hope it was that.??? going for a test run this afternoon.
I'll let you guys know.

Kanookstr

Success!!!! The dip stick tube was the cause of the pinging!!!!
Thanks to all for the suggestions