E.G.R. is not used at idle. E.G.R. is not used on cold engines in most cars. E.G.R. is not used at wide open throttle. We will assume the fuel and ignition systems are working to specs. If car hesitates on light acceleration, has a tip-in sag, or a flat spot when transmission shifts from first to second gear.
Most probable cause is too much E.G.R. flow.
If car pings at cruise or light throttle acceleration, and has no pinging under heavy acceleration, the most probable cause is little or no E.G.R. flow. Possible Causes of Too Much E.G.R. Flow 1. Weak calibration spring in E.G.R. valve. Restricted catalytic converter or exhaust. Idle speed too high.