Knock retard after cam install
Thread Starter
Teching In
Joined: Oct 2005
Posts: 20
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From: Baton Rouge, La
Knock retard after cam install I just installed a TSP Torquer 3 on a 111lsa last week. I had a death in the family so I had no choice but to drive 200 miles to Texas with the car untuned. I took it to get the tune on Wednesday and while tuning, we noticed that I was gettin some knock retard. I am getting 4* at WOT which is the max allowable in my tune. When I am driving around town and get into it (25-50% throttle) the KR jumps around between 1 and 14*. If I keep a steady RPM and throttle position, there is no KR. It seems like it is only happening under a load. I am not sure exactly what would be causing it and would appreciate any input.
On The Tree
Joined: Jan 2006
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I'm sorry for your loss.
Your problem doesn't seem to be fuel enrichment related according to your FTrims and your calculated AFR. I say "calculated" unless you have a wideband AF sensor.
A couple of quick questions.
1. Do you own a stereo system that produces strong deep bass?
I've seen knock sensors produce voltage in these situation tricking the PCM into thinking the engine was pinging.
2.Have you switched brands of gas?
I see you took a trip recently did you have to use a different brand or lower
octane rating?
Have you refueled since this began? Bad gas, maybe.
3.I see you had it tuned. Was it by a pro? With the same gas you normally
use?
If all of this checks out you may just have to tune out some advance in the load cells where you're getting retard.
Your problem doesn't seem to be fuel enrichment related according to your FTrims and your calculated AFR. I say "calculated" unless you have a wideband AF sensor.
A couple of quick questions.
1. Do you own a stereo system that produces strong deep bass?
I've seen knock sensors produce voltage in these situation tricking the PCM into thinking the engine was pinging.
2.Have you switched brands of gas?
I see you took a trip recently did you have to use a different brand or lower
octane rating?
Have you refueled since this began? Bad gas, maybe.
3.I see you had it tuned. Was it by a pro? With the same gas you normally
use?
If all of this checks out you may just have to tune out some advance in the load cells where you're getting retard.
Last edited by LS1_TA_2002; Apr 30, 2007 at 01:11 PM.
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Thread Starter
Teching In
Joined: Oct 2005
Posts: 20
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From: Baton Rouge, La
ls1_ta_2002, My stereo is stock with replacement door speakers. I have been thinking that it could be bad gas as I filled up right before I took it to get tuned and noticed the knock right after that, but I did not really check it before that tank of gas, but I am going to drain the rest of this tank tomorrow and start over with a new one and see what happens. And yes, the car was professionally tuned by a very respected tuner in this region. Thank you for the input, I will check on the timing tables to see if that is it also.
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Brett Foote
TECH Apprentice
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I'm going after the knock sensors and since I'm in there I'm going to swap out the map sensor..
I've got detonation occuring at low rpm and the computer doing nothing till it gets so bad that the pcm reacts hard and performance/drivability suffers..
I could be wrong but I think thats whats happening...I'm running shell high test.
Since the knock sensors are not that expensive, nor are the map sensors...the labors not a big deal (about an hour?) I'm heading in that direction..
Been tuned 8 times...4 different tuners and I've changed the maf, the fuel filter,(including regulator) the coolant temperature sensor, the injectors, the plugs, the wires and checked and cleaned all the grounds...(02 sensors are moving good and fast so I haven't changed them)
I'm hoping this is the fix as I can't figure out why I'm getting such overractive knock sensors (assuming they are not picking up the mild detonation all LS motors see and mildly react to) By the time the knock sensors react....the pcm really pulls timing etc and the performance goes in the crapper.
I'll report back next week and let you know if it works and stops the detonation and knock retard.
I've got detonation occuring at low rpm and the computer doing nothing till it gets so bad that the pcm reacts hard and performance/drivability suffers..
I could be wrong but I think thats whats happening...I'm running shell high test.
Since the knock sensors are not that expensive, nor are the map sensors...the labors not a big deal (about an hour?) I'm heading in that direction..
Been tuned 8 times...4 different tuners and I've changed the maf, the fuel filter,(including regulator) the coolant temperature sensor, the injectors, the plugs, the wires and checked and cleaned all the grounds...(02 sensors are moving good and fast so I haven't changed them)
I'm hoping this is the fix as I can't figure out why I'm getting such overractive knock sensors (assuming they are not picking up the mild detonation all LS motors see and mildly react to) By the time the knock sensors react....the pcm really pulls timing etc and the performance goes in the crapper.
I'll report back next week and let you know if it works and stops the detonation and knock retard.
Last edited by JBsZ06; May 14, 2007 at 09:06 PM.
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From: Central Cal.
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I am JBsZ06 and it's been a long time. Bel ieve it or not for me in my c5 z06 it was an unseen cracked header that was not known at the time. It would throw off the air fuel mixture with the 02s.
After replacing the headers if I remember correctly the air fuel mixture was correct and the problem resolved.
Eventually the double timing chain snapped and took out the top end of the motor. I sold the z06 and bought a c6 which with a few small mids made around 450 hp instead of 436 ho and I drove that as my daily for 143k utterly reliable miles. I sold that beautiful corvette for 11 grand because even though it was running great..I had 143k miles on it. Picked up my C8Z51 the next day and have been partying ever since..
My opinion for what it's worth is look for a basic cause of incorrect air fuel mixture a.
For that car at that time. I believe it was the headers that needed to be replaced..all the shops I had been to missed it. A hole by the bracket if I remember correctly
Good luck and I hope this helps in some way
After replacing the headers if I remember correctly the air fuel mixture was correct and the problem resolved.
Eventually the double timing chain snapped and took out the top end of the motor. I sold the z06 and bought a c6 which with a few small mids made around 450 hp instead of 436 ho and I drove that as my daily for 143k utterly reliable miles. I sold that beautiful corvette for 11 grand because even though it was running great..I had 143k miles on it. Picked up my C8Z51 the next day and have been partying ever since..
My opinion for what it's worth is look for a basic cause of incorrect air fuel mixture a.
For that car at that time. I believe it was the headers that needed to be replaced..all the shops I had been to missed it. A hole by the bracket if I remember correctly
Good luck and I hope this helps in some way
