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K5 Blazer 1969-1994
While this model ended its run, it is not uncommon to see them on the road or off, years after production end.
Platform: Truck, GMT 400

Spark knock issues

Old December 26th, 2010, 7:06 PM
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Default Spark knock issues

hello everyone, I'm new to the chevy world having owned and raced nothing but 5.0 mustangs. I know how to work on them but my blazer is a different thing. I traded a friend of mine a mustang for this 1992 k15 blazer with a 5.7 and 700r4 trans. the motor was replaced about 6 months ago by him. he got a crate motor from orielly's thats rated at 290hp. he said that the original engine was rated around 210- 230 hp. it has TBI. it runs good until you really punch it then it spark knocks. I took it to a very good local shop where they reset the timing for me. they set it a "0" tdc. I can only guess that the knock sensor may be bad. I know its not good for this engine to spark knock, and it seems to run a tad rich after warm up. I going to guess that this injection system runs in open loop until proper engine operating temps are reached then goes closed loop. I get a gasoline smell from the exhaust after it has warmed up. the spark knock is really bad if you try to accelerate up a hill and put the enigine under load. any ideas you may have will be greatly appreciated

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Old December 27th, 2010, 5:16 PM
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change the spark knock sensor on the block
it is on the engine block below the right side (passenger) exhaust manifold and what you need to do is unplug it and set your meter to ohms and check the resistance between the sensor terminal and the engine block it should read 3300-4500 ohms. If not then replace it.

Last edited by 2wd-K5; December 27th, 2010 at 5:18 PM.
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Old December 27th, 2010, 9:07 PM
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many thanks, I will try that very soon as I have to go back to work for the next 2 days. Your information is greatly appreciated.


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Old December 28th, 2010, 11:50 AM
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no problem, whats the point of knowledge if u dont share it
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