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this one has me stumped

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Old June 18th, 2012, 9:48 PM
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Default this one has me stumped

Have a 1996 gmc savana 3500 replaced the oxygen sensor because it had started pinging a little. New sensor made it start knocking bad, put the old one back in and it went back to pinging, wrong sensor ,any thoughts
Old June 18th, 2012, 10:13 PM
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what grade fuel are you using? try using a higher octane fuel.
Old June 18th, 2012, 10:16 PM
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So the truck should have 4 o2 sensors, did you replace all of them?Or at least the 2 upstream. Regardless it is most likely not the problem. Is the check engine light on? What is the code?
Old June 18th, 2012, 11:59 PM
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No check engine lite, but there is only one sensor
Old June 19th, 2012, 11:58 AM
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Look again and closer. There is always 2 sensors for each bank. A pre catalytic and one after the catalytic converter. Maybe someone has made some changes over the years.
Old June 19th, 2012, 4:06 PM
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Probably not your o2 sensor. An inoperative EGR valve will cause light pinging. No exhaust gas recirculation will raise combustion temperatures to the point of light pinging. Chevy dropped the EGR valve on some later vehicles but I believe yours has one. Usually the back pressure valve in the EGR gets plugged and prevents the valve from opening.
Old July 2nd, 2012, 8:57 PM
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Thanks for the info, I will look into that. Tried to drive truck today and it acted just fine until it got up to operating temp then started to nknock again
jim
Old July 3rd, 2012, 12:28 AM
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Strange. The engine has a knock sensor to retard timing which prevents pinging before your ear ever hears it. If it's working right, no ping. If it's not, you should get an error code.
I'd scan the truck just for fun, wouldn't be the first time someone had a stored code without the SES light being on. AutoZone will do it for free.
Old July 3rd, 2012, 7:32 PM
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Good point thanks
Old July 3rd, 2012, 7:38 PM
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Default truck not running right cannot figure it out need help

i have a 1996 chevy 1500 5.7 vortec and i its not running right i have replaced the fuel filter, fuel pump delfi pump, it jumps when i go to take off its definately an electrical problem but cannot figure out what it could be put new plugs and wires in it and still nothing if anyone has any tips or has had this happen to them it would be great for any ideas or help, new to this site gonna give it a try thanks
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