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Hi Everyone - I just bought a 94 Fleetwood with 50k miles on it about a month ago and it pings under certain light to medium load situations on 87 octane. Heavy or full throttle - no problems.

I did some research on this board (used to have an Impala SS many years ago and you guys always know more than typical Caddy guys) and checked the diagnostic mode for codes - there are none. Also used seafoam through the brake booster vacuum hose to see if it was carbon buildup and that made no difference, although most of the smoke seemed to only come from the passenger side exhaust pipe?

Any suggestions on what to try next? Other than this the car runs great ? :confused:

Thanks!
 

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LIGHT pinging is OK, or so they say. Heavy, knocking detonation would be bad. These engines have knock sensors that pick up detonation and the PCM then cuts spark advance to control it.

The EGR check is 2 parts. First, push up on the EGR diaphragm while the engine is running. It should stumble. This indicates that your EGR and passages are not clogged. Next, with the enigne off, disconnect the vacuum supply line to the EGR, push the diaphragm up, block the vacuum port with your finger and release the diaphragm. It should stay open. If the diaphragm moves back to the closed position, the EGR valve is defective.
 
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