LT1 knock sensor is picking up knock, giving me bad spark retard and timing
02-18-2006, 03:04 PM
#1
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LT1 knock sensor is picking up knock, giving me bad spark retard and timing
I really notice the problem while driving about 25 mph and stomping on the gas pedal. The engine sounds like marbles in a spray can or really bad timing. I dont have a laptop (only a desktop) so i cant see that data while driving. While parked i rev the engine and sometimes hear something but almost always the datamaster program picks up spark retard of up to 8 degrees max. Only happens if i rev the engine quickly. Usually happens around 2000 rpm. Doesn't matter what temp the engine is but it gets worse as the engine warms up. Running 91 octane gas.
Other than this problem the car runs awesome.
This is what i have done to try to fix it...
Swapped KM, pcms, MAF from another LT1. Put in new knock sensor. Programmed in original tune, still doing this.
Other than this problem the car runs awesome.
This is what i have done to try to fix it...
Swapped KM, pcms, MAF from another LT1. Put in new knock sensor. Programmed in original tune, still doing this.
02-18-2006, 03:16 PM
#3
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Re: LT1 knock sensor is picking up knock, giving me bad spark retard and timing
Fuel Pressue is good (42-44psi).
Lt1 has about 100K miles
The exhaust smells weird at full throttle but i have the egr and charcol canister removed and everything capped.
I know nothing about the age of the O2s. They are probably the originals.
This is also my last problem to fix in my engine swap. I have new plugs, new wires. Have replaced intake manifold gasket, valve cover gaskets also.
Lt1 has about 100K miles
The exhaust smells weird at full throttle but i have the egr and charcol canister removed and everything capped.
I know nothing about the age of the O2s. They are probably the originals.
This is also my last problem to fix in my engine swap. I have new plugs, new wires. Have replaced intake manifold gasket, valve cover gaskets also.
Last edited by FirebatLT1; 02-18-2006 at 03:30 PM.
02-18-2006, 03:32 PM
#4
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Re: LT1 knock sensor is picking up knock, giving me bad spark retard and timing
hmm...
let me think about it
also, the marbles you are hearing IS spark knock, so do not drive it until it is fixed, prolonged knock destroys pistons
let me think about it
also, the marbles you are hearing IS spark knock, so do not drive it until it is fixed, prolonged knock destroys pistons
02-18-2006, 05:45 PM
#6
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Re: LT1 knock sensor is picking up knock, giving me bad spark retard and timing
about how many gallons of high octane gas would i need? I have about a 3/4 tank of 91 octane in right now. I think i can get some 100 or 110 octane locally.
02-18-2006, 06:13 PM
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Re: LT1 knock sensor is picking up knock, giving me bad spark retard and timing
Originally Posted by FirebatLT1
about how many gallons of high octane gas would i need? I have about a 3/4 tank of 91 octane in right now. I think i can get some 100 or 110 octane locally.
02-19-2006, 06:01 PM
#10
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Re: LT1 knock sensor is picking up knock, giving me bad spark retard and timing
Originally Posted by Injuneer
What gear are you in when you floor it at 25mph?
I've done it in 3rd and 2nd. When in 1st the rpms are too high. I thought it was the torque convertor before so i swapped that with a spare convertor, still did the same thing.
I can get it too make the marble sound (barely can hear it) while in park but only when its warmed up all the way and by quickly stomping on the accelerator.
Another thing i did notice was that i dont have a ground strap or the copper braided strap that goes from the ground on the coil to the chassis like the stock LT1 cars do. Think this would cause a problem?
I have a spare used opti I could put on. Do you think the opti is a possiblility?
My Lt1 came out of a wrecked car with front end damage so it could have rained on the opti before i got it.
Last edited by FirebatLT1; 02-19-2006 at 06:14 PM.
02-20-2006, 07:08 PM
#11
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Re: LT1 knock sensor is picking up knock, giving me bad spark retard and timing
since it happens it open loop, it can't be the O2 sensors then, right??
I think this is the 3rd batch of gas i've had it on, so not the gas.
My suspects are the opti, fuel injectors. I've tested the coil with a meter and it was within spec.
Unless something is actually wrong inside the engine.
I think this is the 3rd batch of gas i've had it on, so not the gas.
My suspects are the opti, fuel injectors. I've tested the coil with a meter and it was within spec.
Unless something is actually wrong inside the engine.
Last edited by FirebatLT1; 02-20-2006 at 07:12 PM.
02-24-2006, 01:41 PM
#12
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Re: LT1 knock sensor is picking up knock, giving me bad spark retard and timing
I've swapped plugs, fixed a header leak(hopefully), checked fuel pressure reg and injectors. Ran datamaster to see whats going on now.
At idle - For BLMs i'm seeing 108 on both sides when fully warmed up. The IAC slowly falls to zero and reaches zero when the engine warms up to about 175 degrees. Tried adjusting the throttle stop, nothing changing the IAC.
So, Vacuum leak or bad IAC???? IAC does change value (increases) when i press on the throttle.
At idle - For BLMs i'm seeing 108 on both sides when fully warmed up. The IAC slowly falls to zero and reaches zero when the engine warms up to about 175 degrees. Tried adjusting the throttle stop, nothing changing the IAC.
So, Vacuum leak or bad IAC???? IAC does change value (increases) when i press on the throttle.
Last edited by FirebatLT1; 02-24-2006 at 01:43 PM.
02-24-2006, 03:51 PM
#13
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Re: LT1 knock sensor is picking up knock, giving me bad spark retard and timing
Originally Posted by FirebatLT1
I've swapped plugs, fixed a header leak(hopefully), checked fuel pressure reg and injectors. Ran datamaster to see whats going on now.
At idle - For BLMs i'm seeing 108 on both sides when fully warmed up. The IAC slowly falls to zero and reaches zero when the engine warms up to about 175 degrees. Tried adjusting the throttle stop, nothing changing the IAC.
So, Vacuum leak or bad IAC???? IAC does change value (increases) when i press on the throttle.
At idle - For BLMs i'm seeing 108 on both sides when fully warmed up. The IAC slowly falls to zero and reaches zero when the engine warms up to about 175 degrees. Tried adjusting the throttle stop, nothing changing the IAC.
So, Vacuum leak or bad IAC???? IAC does change value (increases) when i press on the throttle.
02-25-2006, 09:21 AM
#15
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Re: LT1 knock sensor is picking up knock, giving me bad spark retard and timing
The 108 BLM's indicate the PCM thinks its running rich, and has bottomed out the long term fuel corrections, trying to solve what it thinks is the problem. If it really isn't running rich, the BLM's might be pulling out fuel when they aren't supposed to, and causing it to run lean. You need to find out why the BLM's are so screwed up.