J
jamesblankman4002
Guest
The writer is a controls engineer for the automotive industry and has ASE certification in this area.
1994 Chevy Camaro 3.4L intermittently detonates whether at idle or at road speeds. It is not due to egr or fuel trim or anything like that. It detonates because the ECM advances the timing on its own. For example, when driving during a "fit" if you accelerate, MAP vacuum drops (pressure increases as throttle plate opens) you would expect timing to retard. Instead it advances, the knock sensor does its job but is still too far advanced. It detonates and ruined the rod bearings after only 10,000 miles. By the time it was brought to me it had most sensors replaced and new EGR valve.
Thinking it was an algorithm gone sour (did a table lookup for timing data backwards or something) I replaced the ECM. It still does it. Not sure what's going on now. Any ideas are very welcome. jamesblankman4002@hotmail.com
1994 Chevy Camaro 3.4L intermittently detonates whether at idle or at road speeds. It is not due to egr or fuel trim or anything like that. It detonates because the ECM advances the timing on its own. For example, when driving during a "fit" if you accelerate, MAP vacuum drops (pressure increases as throttle plate opens) you would expect timing to retard. Instead it advances, the knock sensor does its job but is still too far advanced. It detonates and ruined the rod bearings after only 10,000 miles. By the time it was brought to me it had most sensors replaced and new EGR valve.
Thinking it was an algorithm gone sour (did a table lookup for timing data backwards or something) I replaced the ECM. It still does it. Not sure what's going on now. Any ideas are very welcome. jamesblankman4002@hotmail.com