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phantom KR without knock sensors

9

97gpl36

New member
Good day to everyone,I was wondering why I'm getting up to 16* KR between 1700-2500 RPMs. I can feather the throttle and get past it sometimes,or just nail it from stoplight to get rpm higher and hope the cops aren't around. Replaced knock sensors even though they were doing their job.
KR was so bad last night that I unplugged both sensors at the PCM and still had an occasional 1-3 KR between 1800-2400 rpm.
Anyone have an idea to what's going on? This thing is driving me nuts.
Still have PO171 and PO300,can't find any vac leaks and ltft is16 @ idle.
3.8 n/a has about 4k on engine,and lim gaskets were replaced around 1k ago.
Please help, thank you.
 


Check to see if your downpipe is hitting the front sway bar. They're close and if a motor or trans mount is bad it may be hitting and sending the false KR.
 
Thanks all,I know my dog bone mounts are shot and I even secured them by running a large bolt with rubber around it to keep the engine from moving,it used to chatter your teeth when in the car but it doesn't do that anymore.
I was thinking about some poly mounts.
I know my sway bar and down pipe are not touching,and I just got rid of my u-bend,cat,and resonator. Wondering if that could be an issue.
As for the vac. leaks,no externals can be found,new metal LIM gaskets,LIM looked great after cleaning,UIM and gaskets are brand new.
I even vac. tested all of the vacuum related sensors and EVAP switches,misfires stop and LTFT decreases after 1200 rpm.
I'm thinking internal vacuum leak at LIM.
Hopefully not a head gasket with less than 5k on rebuild.
 
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