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Pinging on 87

dvzzz

By dvzzz
in Engines & Drivetrain

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dvzzz Enthusiast

dvzzz

Posted
Posted (edited)

Hope someone can help me troubleshoot it. 

2020 Tahoe LS with 5.3, 6-speed, 31K miles. I have tried Exxon, Mobil, BP, Shell 87 gas. On 87 and often on 89 truck pings on highway trips, I am cruising 65-70 MPH, engine is always hovering around 1800-2000 and when I am trying to maintain the speed or add just a bit of throttle uphill it pings for 1-2 secs and then it downshifts and no pinging in the lower gear but once again at 70 MPH crusing around 1900 RPMs, if I am to touch the throttle it would ping/lug. 

With 89 it happens less, with 93 no pinging. I run Mobil 1 EP, Shell Gas Truck,  Valvoline Modern Engine oil with the AC Delco filter. Change oil every 4500 miles.

Dealer, of course, " cannot reproduce the issue". This truck is designed to run 87 fine and many many on these forum run 87 with zero knock issues, in my case, unless I run 93 it pings. Pinging is bad, thus what can I do to get the dealer/GM to accept the issue and fix it? With gas prices at $4.50 for 93 grade, it is now very noticeable to fill up as Regular vs. Premium is $1+ spread. Appreciate thoughts.

 

Here are the logs from September for Knock ****** events. The CSV file is here as well Driving Logs with Knock events

 

 

knock_1.thumb.png.d4c6de13ac5920ccb3fc597d63796896.png

 

knock_throttle_position.thumb.png.f74383ed32e4b6c6fc0f9e9f8019e415.png

total_knock.png

Edited by dvzzz
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shakenfake Senior Enthusiast

shakenfake

Posted
Posted

Are you getting codes? It is pretty common for these trucks to ping on 87 from what I have read

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dvzzz Enthusiast

dvzzz

Posted
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Posted
1 minute ago, shakenfake said:

Are you getting codes? It is pretty common for these trucks to ping on 87 from what I have read

 

No codes ever, not even short-term. What concerns me that it pings even on 89 sometimes. 

M1ck3y Senior Enthusiast

M1ck3y

Posted
Posted

They all do it, just don't let it lug. Press the throttle down a bit further to get that down shift, or drop it into L. 

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dvzzz Enthusiast

dvzzz

Posted
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Posted
9 minutes ago, M1ck3y said:

They all do it, just don't let it lug. Press the throttle down a bit further to get that down shift, or drop it into L. 

Understood. The most annoying part that it happens at the exact crusing RPM and if I tip in to maintain speed it happens almost all the time, to avoid it I have to press harder to downshift breaking the cruising. 

M1ck3y Senior Enthusiast

M1ck3y

Posted
Posted
54 minutes ago, dvzzz said:

Understood. The most annoying part that it happens at the exact crusing RPM and if I tip in to maintain speed it happens almost all the time, to avoid it I have to press harder to downshift breaking the cruising. 

 

Can you hear the knock?

 

I know mine doesn't like hills... Over time I trained myself to listen for it so I know whether to give it throttle, back off, or initiate a downshift.

 

Not easy with the injector sound. It will usually feel a little different under knock too. This is on 94.

 

I think there's the people that are aware and change their driving style to accomadate the knock. Then there's the people that don't know the difference and just drive it. 

 

Hard to say who's doing it right.

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dvzzz Enthusiast

dvzzz

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Posted (edited)
9 minutes ago, M1ck3y said:

 

Can you hear the knock?

 

I know mine doesn't like hills... Over time I trained myself to listen for it so I know whether to give it throttle, back off, or initiate a downshift.

 

Not easy with the injector sound. It will usually feel a little different under knock too. This is on 94.

 

I think there's the people that are aware and change their driving style to accomadate the knock. Then there's the people that don't know the difference and just drive it. 

 

Hard to say who's doing it right.

 

Indeed, I can hear it, I pay attention to my truck, in fact too much attention, I baby this machine, perhaps better to gun it down and drive like a maniac 😄 that will keep the plugs clean, IVD burnt off and oil pressure up. 

 

It is very irrational that I like GM products, my Yukon was a Lemon, this one it generally OK, some rattles and pinging. These full size trucks do drive nicely on highways and they are SO quiet that I can hear pinging very clearly.

 

Edited by dvzzz
CamGTP Senior Enthusiast

CamGTP

Posted
Posted

I hear something too and I even run E85 50% of the year, the logs from HP Tuners rarely show knock.

 

Doesn't really bother me though, it's fine. I put money on the injectors and high pressure fuel pump near the firewall. I also think there was some sort of TSB for noise coming in through the power steering boot on the firewall.

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rlcole321 Enthusiast

rlcole321

Posted
Posted

You could try a "reset", clear memory by disconnecting the batt. over night then drive it around till operating temp., then try to duplicate.  Also, with a tuner possibly you could change the "Tip in" timing curve, to help that, but of course not sure if a small change is able with say a HP Tuner. I have an 18 Rado L83, but I choose to run 93 cause Buc-ees station here has CHEAP 93, 40 to 60 cents cheaper than anybody else.

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14burrito Enthusiast

14burrito

Posted
Posted (edited)

Its low mileage but do you have any oil consumption?

Plugs look OK?

Compression good?

 

Id try a can of seafoam through the intake to clear up the valvetrain. I wonder if there isn't some coking on the valves, carbon dropping into the cycling causing pre-ignition.

Edited by 14burrito
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dvzzz Enthusiast

dvzzz

Posted
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Posted (edited)
39 minutes ago, 14burrito said:

Its low mileage but do you have any oil consumption?

Plugs look OK?

Compression good?

 

Id try a can of seafoam through the intake to clear up the valvetrain. I wonder if there isn't some coking on the valves, carbon dropping into the cycling causing pre-ignition.

Good points and:

1) catch can from day 1 and it does catch but not water or milky stuff but oil with some fuel in it

2) plugs look OK

3) it consumes with Mobil 1 EP but not more than 1/3 of a quart over 4500 miles and zero consumption with Rotella Gas Truck

4) CRC Intake Valve cleaner was run through the intake

4) did not check the compression 

Edited by dvzzz
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  • 2 weeks later...
dvzzz Enthusiast

dvzzz

Posted
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Posted

Good time of day-

the graph below shows both spark timing advance and total knock retards. Are these timing advances normal?

 

 

Screen Shot 2021-11-18 at 20.45.32.png

Grumpy Bear Senior Enthusiast

Grumpy Bear

Posted
Posted

Your ECU can not measure octane. It is always looking for the incipient detonation point where fuel efficiency is peaked. So as anything looking for the edge it steps off the curb now and again. It's also a 'learning' system. You will notice that when you run 87 for several tanks it will find a 'base line' and will still step over. However if you then run a few tanks of 93 then go back to 87 the number of ****** events will be much higher until it again finds your new constant. It will never get perfect unless you pull timing from the map. Some hand held canned tunes call this an 87 tune. 

 

It's quite normal and not destructive. 

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dvzzz Enthusiast

dvzzz

Posted
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Posted

@Grumpy Bear thank you. I found one interesting fact today while trying to troubleshoot.

 I just went for a long drive and logged again. While logs shows few KR events, up to 4 degrees. There was no audible pinging, same tank of fuel, same load, same route. What was different - the outside temperature, it is finally cold in NC, outside temp was ~42. I could not hear a single pinging event, before it was very audible almost all the time. What sensors might be to blame here? I thought maybe active shutters on Tahoe do not open fully but temp gauge does not show overheating ever. Is MAF also a temp sensor?

  • Like 1
JimCost2014 Senior Enthusiast

JimCost2014

Posted
Posted
1 hour ago, dvzzz said:

@Grumpy Bear thank you. I found one interesting fact today while trying to troubleshoot.

 I just went for a long drive and logged again. While logs shows few KR events, up to 4 degrees. There was no audible pinging, same tank of fuel, same load, same route. What was different - the outside temperature, it is finally cold in NC, outside temp was ~42. I could not hear a single pinging event, before it was very audible almost all the time. What sensors might be to blame here? I thought maybe active shutters on Tahoe do not open fully but temp gauge does not show overheating ever. Is MAF also a temp sensor?

A short movie to watch if you can not find anything on Netflix:

 

 

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