94 Chevy K1500 retards timing instead of advancing

Timing is dead on at 0 degrees. Runs ok at idle, but if you push the throttle, it jumps the timing waaaay retarded, instead of advancing it. I'm at a loss for what is going on with it, but have two ideas - Could it be a bad PROM? or bad ECM? Someone help!! Please!!

A bad knock sensor can retard the timing; although, I am not sure how much it retards the timing.

Try disconnecting the knock sensor at the engine block. My 90 only has one but at some point (not sure of the year) they went with two. So if you have 2 disconnect both of them.

You can also check the knock count with a scan tool. If the count is high, the sensor is probably bad.

//2000CAYukon

I'm not sure that it's the knock sensor. It will idle fine with the timing at 0 degrees. When I hit the gas, the timing jumps to like 20 degrees AFTER TDC. It almost seems like the ECM isn't advancing the timing at all.

I'm not sure that it's the knock sensor. It will idle fine with the timing at 0 degrees. When I hit the gas, the timing jumps to like 20 degrees AFTER TDC. It almost seems like the ECM isn't advancing the timing at all.

When the knock sensor goes bad, it picks up "false" knock and the ECM will retard the timing. Disconnecting the sensor and testing will verify it this is happening.

//2000CAYukon