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Old 03-01-2012, 03:15 PM
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Engine knock

I have a 1993 Caprice Classic LTZ 5.7. The knock sensor sets off the service engine soon light. This occurs when I accelerate to reach higher RPM and speed out on the highway. I am unable to enjoy the ride after the light comes on, the vehicle begins to act as if it were bogging out.

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Old 03-01-2012, 03:51 PM
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Have you replaced the sensor? The knock sensors job when it hears knock is to retard the spark timing, and it will keep retarding it until the knock stops. If the knock doesn't stop it keeps retarding it until the point it starts to run erratic. So in this case this would either point to the sensor is bad or the car has detonation problems on a high level. First thing I would do is check it for vacuum leaks, and unmonitored air entering the engine causes the mixture to go lean which can cause spark knock. Or it simply could be carbon build up from the car not being floored often enough to clean the soot out. Check it for vacuum leaks and check it real carefully. If none are found the next step would be a seafoam treatment via a vacuum hose on the engine itself.
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Old 03-01-2012, 04:51 PM
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Quote:
Originally Posted by jmartinez
I have a 1993 Caprice Classic LTZ 5.7. The knock sensor sets off the service engine soon light. This occurs when I accelerate to reach higher RPM and speed out on the highway. I am unable to enjoy the ride after the light comes on, the vehicle begins to act as if it were bogging out.
X2 Doublevision and will add EGR out to lunch, and ask what grade fuel you're using?

Bogie
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Old 03-03-2012, 04:56 PM
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Engine knock

[QUOTE=oldbogie]X2 Doublevision and will add EGR out to lunch, and ask what grade fuel you're using.

I have been using 93 octane since the car was bought in the year 1992.
I replaced the EGR valve already.
Someone told me this was caused by the lifters being bad, not all but some.
Do I need to take the engine apart and replace the lifters?
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Old 03-04-2012, 11:03 AM
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[QUOTE=jmartinez]
Quote:
Originally Posted by oldbogie
X2 Doublevision and will add EGR out to lunch, and ask what grade fuel you're using.

I have been using 93 octane since the car was bought in the year 1992.
I replaced the EGR valve already.
Someone told me this was caused by the lifters being bad, not all but some.
Do I need to take the engine apart and replace the lifters?
There's more to it than just the EGR valve. I was remiss in making it look that simple. The EGR on is controlled by a separate solenoid that takes info from the computer. This system is subject to vacuum leaks and electrical problems in that circuit. But a failure should set a code which is probably 32 though not always.

Bogie
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