Check Engine Light - Ahhh!

[cuervo]

Hey all,

I have an 87 GMC Jimmy fullsize.

I put a pace performance crate motor in it and it is running fine except for one thing.

When I towing my boat or getting on it a bit the valve train will rattle a little and the check engine light comes on. Well that is the it rattles a little and then it seems like the knock senor reads it then retards the timing and the rattle stops. About 2 seconds later the check enging light comes on. After shutting the motor off and restarting the light is out and it seems fine.

When I installed the motor I put a new knock sensor in and disconnect the brown timing wire before I timed the motor.

Anyone have any ideas on this? The ECM code is 43 which is knock sencor. I check the wire and it is still pluged in.

Thanks!

 

[MTBLAZER89]

Is the engine actually pinging? What's the compresion on the motor? Try running higher octane. /forums/images/graemlins/waytogo.gif

 

[cuervo]

It really doesn't sound like a ping but I guess it could be predetonation. It is a factory crate motor with stock compression ratio. I would think for 87 EFI that would be 8to1 nothing more.

Changing to a higher Octane at current prices is NOT an option.

 

[K5MONSTERCHEV]

Good old code 43, I have the same problem with my TPI 350, havent gotten to diagnose it yet.

The valve train you say is rattling is most likely detonation. If you overtorqued the knock sensor that would make it TOO sensitive and retard the timing, when it doesnt need to be. How tight did you tighten it?

 

[4X4HIGH]

You might try the ESC (electronic spark control) box, and make sure the knock sensor is the correct type.

 

[dyeager535]

Go back, re-time the engine, and take out 2* to see if it goes away.

Take out timing in 2* increments until it stops. Performance may suffer, but if you are pinging, it's suffering anyways, and pinging and bad performance is worse than just bad performance.

My TPI setup (RIP lol) pinged at about 6*, while at 4* it was completely eliminated, and I couldn't tell the difference in performance. I could between 6* and 0* though.