Bad knock sensors?
Thread Starter
Drifting
Joined: Oct 2006
Posts: 1,724
Likes: 23
From: Minnesota
Bad knock sensors?
I have a stock 2004 coupe with around 60k miles on the clock. When I run 91 octane and go WOT, it knocks so bad it sounds like its going to explode. When I run 93 octane its still pings (but nothing like 91 octane). I have tested several different gas stations with several tanks of gas and the behavior is the same.
There are no codes.
Is it possible the knock sensors are not functioning and aren't detected as failed by the computer?
Any thoughts?
Thanks for the help!
There are no codes.
Is it possible the knock sensors are not functioning and aren't detected as failed by the computer?
Any thoughts?
Thanks for the help!
Intermediate
Joined: Jun 2010
Posts: 27
Likes: 0
My '99 was doing as you describe with only 30k or so on the clock. I replaced the plugs and the problem went away. What had happened is that 4 of original platinum(?) plugs had lost their "puck". Apparently this was causing some preignition rather than detonation. Maybe pull them and take a look?
Patrick
Patrick
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
The ONLY way to really know if the KR System is working properly and to see what is going on is to DATA LOG the PCM.
There are several ways to do that.
1 Use EFI Live or HP Tuners
2. Purchase a scanner that has the ability to see LIVE SENSOR DATA and monitor the KR outputs and timing
Bill
There are several ways to do that.
1 Use EFI Live or HP Tuners
2. Purchase a scanner that has the ability to see LIVE SENSOR DATA and monitor the KR outputs and timing
Bill
Thread Starter
Drifting
Joined: Oct 2006
Posts: 1,724
Likes: 23
From: Minnesota
My '99 was doing as you describe with only 30k or so on the clock. I replaced the plugs and the problem went away. What had happened is that 4 of original platinum(?) plugs had lost their "puck". Apparently this was causing some preignition rather than detonation. Maybe pull them and take a look?
Patrick
Patrick
Thread Starter
Drifting
Joined: Oct 2006
Posts: 1,724
Likes: 23
From: Minnesota
The ONLY way to really know if the KR System is working properly and to see what is going on is to DATA LOG the PCM.
There are several ways to do that.
1 Use EFI Live or HP Tuners
2. Purchase a scanner that has the ability to see LIVE SENSOR DATA and monitor the KR outputs and timing
Bill
There are several ways to do that.
1 Use EFI Live or HP Tuners
2. Purchase a scanner that has the ability to see LIVE SENSOR DATA and monitor the KR outputs and timing
Bill
I'll put it on a scanner. However, would bad knock sensors cause this? I wouldn't think this would happen with 91 octane on a bone-stock c5.
"My Dad's a TV Repairman"
Joined: Jul 2014
Posts: 471
Likes: 153
From: San Diego
Here in Commiefornia, when the stations switch to the summer blend of gas, a lot of us have WOT pinging issues due to the crappy mix of MBTE / ethanol and gas. I generally use a bottle of Lucas Octane Booster (the only one that actually works for me) with a fill up during the summer months out here. Yes, it's $10, but worth it if your local octane ratings are, shall we say, optimistic. 
My wife's 335i runs about 16 lbs of boost on a pretty agressive JB4 map, and it only runs right with a bottle of the Lucas on top of Chevron or Shell 91. Tried it in the '04, and havn't had pinging issues since.
My wife's 335i runs about 16 lbs of boost on a pretty agressive JB4 map, and it only runs right with a bottle of the Lucas on top of Chevron or Shell 91. Tried it in the '04, and havn't had pinging issues since.
Last edited by Fed Up; Jun 4, 2016 at 01:47 PM.
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Good call. Didn't think of that. Mine had a lot of carbon in it when I tore it down.
Melting Slicks
Joined: Aug 2014
Posts: 2,468
Likes: 460
From: East Windsor NJ
On my first visit to ECS (165 thermo, catch can, street tune) they told me I had detonation at 6000rpm and pulled some timing out of it with marching orders to Seafoam it 3 times. Did that over a period of about 2 months with a few trips to the drag strip with race-gas fill up - when I went back for a checkup I got my timing back - but what you are describing sounds worse....
