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#4548641 - 10/19/17 07:53 PM 2004 Silverado 175k mi; Spark knock issue
TexasTea Offline


Registered: 09/06/13
Posts: 71
Loc: Texas
Hi guys

I've got a 2004 Silverado 5.3L V8 with 175,000 miles that has been having spark knock intermittently since I got the vehicle in 2007 with 65,000 miles. I always use 87 octane fuel

Only in the past 3-4 years have I been actively searching for a resolution but I found that with this cooled down weather here in Houston Texas the spark knock has disappeared and I'm not sure what's the reason

I have an ODBII transmitter with the torque app on my phone tracking the knock retard and timing and the odd thing is that when I actually hear evidence of spark knock occurring, most always under medium to heavy load in gear and at the upper range of RPMs; 3,000-6,000 RPM, no spark knock count is increased nor is the engine computer retarding the timing to compensate

Now all the sudden with the weather cooling off I noticed, again, under the same load conditions mentioned above, the engine started to spark knock only slightly then stopped and all subsequent times I've loaded the engine, when chilly out, the spark knock has disappeared.

Could the heat or hot days be the actual cause of the spark knock? Or does this point to an issue with the gasoline not dealing with high temperatures very well? Perhaps both or something else entirely?

I have done nothing as far as repairs or maintenance to warrant any change in behavior yet now on chilly evenings if I actively attempt to forcefully make the engine spark knock it is not occurring even under the heaviest of loads I'm comfortable putting the engine up to which is pretty high but not stupidly or dangerously high (not maxing it out or anything)

Hoping some of the intelligent and experienced minds on this board can shed some knowledge on this matter so I can better safeguard myself from damaging the engine

Thanks for looking


Edited by TexasTea (10/19/17 07:57 PM)

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#4548663 - 10/19/17 08:16 PM Re: 2004 Silverado 175k mi; Spark knock issue [Re: TexasTea]
kc8adu Offline


Registered: 08/02/05
Posts: 894
Loc: dayton oh
the sensors are in the valley and take on water.
yours are likely beyond dead.

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#4548674 - 10/19/17 08:26 PM Re: 2004 Silverado 175k mi; Spark knock issue [Re: kc8adu]
Chris142 Offline


Registered: 06/05/03
Posts: 16820
Loc: Deplorable in apple valley, ca
Originally Posted By: kc8adu
the sensors are in the valley and take on water.
yours are likely beyond dead.
yep. Just did the ones on the wifes 04 tahoe @160k.
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#4548683 - 10/19/17 08:37 PM Re: 2004 Silverado 175k mi; Spark knock issue [Re: TexasTea]
LeakySeals Online   content


Registered: 02/18/11
Posts: 6574
Loc: Hudson, NH
Did mine this spring. The boots are the real problem. Buy a new harness along with new sensors and seal them down to valley pan good with black rtv. You can do the valley pan gasket and its grommets too while its open . Not hard work. Youtube diy.


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#4548688 - 10/19/17 08:46 PM Re: 2004 Silverado 175k mi; Spark knock issue [Re: TexasTea]
TexasTea Offline


Registered: 09/06/13
Posts: 71
Loc: Texas
Thanks for replying I should've mentioned that both knock sensors were changed about 15-25k miles ago. The rear was corroded add throwing a DTC but regarding spark knock the was no change before or after
Issue persisted same as it stays had been

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#4548692 - 10/19/17 08:49 PM Re: 2004 Silverado 175k mi; Spark knock issue [Re: TexasTea]
StevieC Offline


Registered: 08/21/08
Posts: 17116
Loc: Ontario, Canada
What kind of driving patterns and what kind of mileage. Possible that the coolant sensor is the culprit? I had minor pinging in the Journey that I couldn't seem to remedy with higher octane fuel and then the sensor eventually failed and when I replaced it I got better mileage, the pinging went away as well.
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#4548741 - 10/19/17 09:46 PM Re: 2004 Silverado 175k mi; Spark knock issue [Re: TexasTea]
clinebarger Offline


Registered: 12/19/13
Posts: 1912
Loc: Fort Worth, Texas
Ambient temps have a huge effect on audible spark knock/detonation, I would first suspect incorrect "LOAD" inputs sent to the PCM by the Mass Air Flow Sensor, The Base/Main spark tables are dependent on Cylinder Air Mass Volume calculations derived from the MAF sensor.
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#4548744 - 10/19/17 09:50 PM Re: 2004 Silverado 175k mi; Spark knock issue [Re: TexasTea]
clinebarger Offline


Registered: 12/19/13
Posts: 1912
Loc: Fort Worth, Texas
The PCM monitors knock sensor voltages, Water intrusion will cause the line voltage to be pulled low & set a trouble code/s.
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#4548754 - 10/19/17 10:15 PM Re: 2004 Silverado 175k mi; Spark knock issue [Re: clinebarger]
TexasTea Offline


Registered: 09/06/13
Posts: 71
Loc: Texas
Thank you this is very helpful info I'll inspect the MAF sensor and associated components and adjust accordingly.

Right now I'm getting about 12-14 mpg city
Add I get 15-16 highway (maybe more)

This seems on the low side of average compared to other trucks of this year but it's always been consistent if low


Edited by TexasTea (10/19/17 10:16 PM)

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#4548765 - 10/19/17 10:52 PM Re: 2004 Silverado 175k mi; Spark knock issue [Re: TexasTea]
aquariuscsm Offline


Registered: 12/30/06
Posts: 18170
Loc: Dallas,Tx USA
If you're referring to pinging under acceleration it's probably the [censored] ethanol trash that's forced on us.
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#4548773 - 10/19/17 11:16 PM Re: 2004 Silverado 175k mi; Spark knock issue [Re: TexasTea]
andyd Online   content


Registered: 09/25/04
Posts: 7149
Loc: Marshfield , MA
I'm just tossing out ideas that come to me.The combustion chambers may have enough carbon deposits to cause this. So would a cooling system getting marginal,after time and miles, in hot weather. Pressure cap? Worn out O2 sensor?
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#4549178 - 10/20/17 11:28 AM Re: 2004 Silverado 175k mi; Spark knock issue [Re: clinebarger]
Iowegian Offline


Registered: 01/05/17
Posts: 273
Loc: Iowa
Originally Posted By: clinebarger
Ambient temps have a huge effect on audible spark knock/detonation, I would first suspect incorrect "LOAD" inputs sent to the PCM by the Mass Air Flow Sensor, The Base/Main spark tables are dependent on Cylinder Air Mass Volume calculations derived from the MAF sensor.


My thought too. MAF and/or Air intake temp sensor may give good readings at one temp but bad ones at another temp.
Do you hace readings on the AIT with your scanner? Compare to ambient temp?
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#4549181 - 10/20/17 11:30 AM Re: 2004 Silverado 175k mi; Spark knock issue [Re: andyd]
Iowegian Offline


Registered: 01/05/17
Posts: 273
Loc: Iowa
Originally Posted By: andyd
I'm just tossing out ideas that come to me.The combustion chambers may have enough carbon deposits to cause this. So would a cooling system getting marginal,after time and miles, in hot weather. Pressure cap? Worn out O2 sensor?


Another good idea. Carbon holds heat and in hot weather this could cause predetination.
Higher octane may help if this is the case?
Have you experimented with higher octane fuels to see if this still occurs on hot days?


Edited by Iowegian (10/20/17 11:31 AM)
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#4549183 - 10/20/17 11:33 AM Re: 2004 Silverado 175k mi; Spark knock issue [Re: TexasTea]
Iowegian Offline


Registered: 01/05/17
Posts: 273
Loc: Iowa
Also, what is your long term and short term fuel trim like on normal driving?
Would give more insite.
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2011 Equinox, 2.4l
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#4549259 - 10/20/17 12:59 PM Re: 2004 Silverado 175k mi; Spark knock issue [Re: TexasTea]
Merkava_4 Offline


Registered: 01/30/07
Posts: 17501
Loc: Clovis, CA
Originally Posted By: TexasTea
I should've mentioned that both knock sensors were changed about 15-25k miles ago.


Did that cure your spark knock back then ? Maybe you need to replace them again.

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