Lack Of Power During Hard Acceleration - keywords 7.0 accel accelerate alternator detonate detonation generator knock low LS7 noise retard retarded spark tick timing

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

The customer concern may be a tick or detonation type noise under hard acceleration. To induce this concern, the engine acceleration has to be at least 4000-5000 RPM.

During the tick or detonation noise there may be a noticeable lack of power.

Complete the SI diagnostic for any trouble codes or symptoms found. If diagnostics are inconclusive, and the concern can be duplicated, there may be excessive knock retard during the engine tick noise.

During the noise the technician may notice either the individual cylinder knock detected parameters changing from yes to no, and/or the knock retard reading around 10 to 12 degrees.

If a LS7 engine with low power and an engine tick/detonation noise has been verified, use the chassis ears to see if the noise is coming from the generator.

Monitoring the Ignition 1 Voltage may be another way to verify a generator concern. Normal voltage for this vehicle should be 14 to 14.5 volts. If the Ignition 1 Voltage drops to around 12 to 12.5 volts during the concern, the generator could be the cause of the noise and low power.

If the noise is coming from the generator, replace the generator, and verify the customer concern is repaired.

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.