NEED HELP Light Rumble...

AC75TB07

Original poster
Member
Aug 17, 2019
98
Canada
Since stations switched to winter blend petrol a few weeks ago, my 07 does a little rumbling when you get between approximately 40-50mph...Not anything serious but just something new.

The throttle body has been cleaned as has the MAF. No other recent maintenance... 210,000 Kilometers on the truck.

I've been wondering about the possibility of new spark plugs? Can I do plugs without coils?

No codes...

Thoughts?
 

Mooseman

Moderator
Dec 4, 2011
26,103
Ottawa, ON
New plugs couldn't hurt especially if they are due to be replaced. Get only genuine ACDelco 41-103 plugs (there are fakes out there on Amazon and eBay).

The rumble may be from something else, like the torque converter clutch engaging.
 

AC75TB07

Original poster
Member
Aug 17, 2019
98
Canada
Hummm... Is that, um, a really bad thing? Does it mean anything for the life of the transmission?
 

Mooseman

Moderator
Dec 4, 2011
26,103
Ottawa, ON
It could send shrapnel into the transmission but it's mostly annoying. There are things that can be done to stop it like a shift kit:


To confirm this, while holding a steady speed with the right foot and the shudder happening, tap your brake pedal with your left foot. If the shudder stops, it's confirmed. It is a common issue.
 

AC75TB07

Original poster
Member
Aug 17, 2019
98
Canada
It could send shrapnel into the transmission but it's mostly annoying. There are things that can be done to stop it like a shift kit:


To confirm this, while holding a steady speed with the right foot and the shudder happening, tap your brake pedal with your left foot. If the shudder stops, it's confirmed. It is a common issue.

At higher speeds it did seem to stop for a second a couple times I hit the brake, but it was kinda hard to be sure at lower speeds...
 
New plugs couldn't hurt especially if they are due to be replaced. Get only genuine ACDelco 41-103 plugs (there are fakes out there on Amazon and eBay).

The rumble may be from something else, like the torque converter clutch engaging.
CONFIRMED counterfeit plugs purchased from an "Amazon affiliate"; a dirtbag operating out of Forney Texas. I sent these photos and others to GM, who replied that the plugs in question were "Not authentic".

2020_Trailblazer_Spark_Plugs_LG_03.jpg

2020_Trailblazer_Spark_Plugs_LG_01.jpg
 

AC75TB07

Original poster
Member
Aug 17, 2019
98
Canada
Keep seeing stuff about these counterfeit products. I wonder sometimes if it even matters... I see stuff on Amazon at good prices that are aftermarket brands with great reviews from buyers. Add to that the prices at my local parts store for OEM Ac Delco parts are OMG expensive... x6...🤯
 
Dec 5, 2011
603
Central Pennsylvania
Just throwing this out there.... wheel bearings.
It would be happenstance if your wheel bearings started rumbling as the winter blend changeover occurred.... but I personally have a VERY pronounced rumble that hits a strong resonance at a specific speed (about 70 mph for me). The dead giveaway that my problem is wheel bearings is that the sound virtually disappears in turns. My rumble appeared out of nowhere with no real warning.

I would say you should consider the front wheel bearings as the source of your rumble if the rumble occurs at a specific mph vs a given RPM under load.
 

AC75TB07

Original poster
Member
Aug 17, 2019
98
Canada
Believe me, I've had SO much experience with wheel bearings that I think I would know the sound if I was in the morgue... So I don't think it's that.

I called it a rumbling but you could also call it a kind of vibration aswell when you hit like a bit above 40mph... Thankfully it doesn't seem to be getting any worse and is more of an annoyance... I can live with it for a little while until I figure out what it is and how to pay for it...UGH!
 

Redbeard

Member
Jan 26, 2013
3,606
Keep seeing stuff about these counterfeit products. I wonder sometimes if it even matters... I see stuff on Amazon at good prices that are aftermarket brands with great reviews from buyers. Add to that the prices at my local parts store for OEM Ac Delco parts are OMG expensive... x6...🤯

Yep, it does matter. The original ACDelco 41-103 irridium plugs easily last 100,000 miles. I pulled mine at 90k miles and they looked like new. I purchased ACDelco 41-103 through Amazon and received Counterfeit plugs. Never again will I order plugs through amazon and Amazon would not let me write a negative review on them! :Banghead:For me I don't want to break down on the road a long way from home due to a counterfeit product I know might be bad ( or worse with my wife -cause I might never hear the end of it either. lol. ). Just my 2 cents.
 
  • Like
Reactions: Mooseman

AC75TB07

Original poster
Member
Aug 17, 2019
98
Canada
Yep, it does matter. The original ACDelco 41-103 irridium plugs easily last 100,000 miles. I pulled mine at 90k miles and they looked like new. I purchased ACDelco 41-103 through Amazon and received Counterfeit plugs. Never again will I order plugs through amazon and Amazon would not let me write a negative review on them! :Banghead:For me I don't want to break down on the road a long way from home due to a counterfeit product I know might be bad ( or worse with my wife -cause I might never hear the end of it either. lol. ). Just my 2 cents.

No no, I didn't mean buying counterfeit products didn't matter; you have no clue what they are at all. Just that maybe some of the other legit brands might be OK to use instead of AC Delco since half time you're not even getting the real thing...
 
  • Like
Reactions: Redbeard
Dec 5, 2011
603
Central Pennsylvania
Believe me, I've had SO much experience with wheel bearings that I think I would know the sound if I was in the morgue... So I don't think it's that.

I called it a rumbling but you could also call it a kind of vibration aswell when you hit like a bit above 40mph... Thankfully it doesn't seem to be getting any worse and is more of an annoyance... I can live with it for a little while until I figure out what it is and how to pay for it...UGH!
You have to go with your gut.... but keep an open mind, just in case.
I was convinced my rumbling was just tire/road noise as I have some rather aggressive tread... until my ABS started to occasionally "brrrrt" at low speed pulling out of the garage. That's when I started to notice that the rumbling changed in turns... only then did the penny drop for me.

Have you looked for exhaust leaks? I had an exhaust crossover pipe split open on me due to rust (it was the cheapest POS I'd ever seen when I removed it.) I thought someone had stolen my cat...

Regardless, good luck. Keep us posted...
 
  • Like
Reactions: AC75TB07

mrrsm

Lifetime VIP Donor
Supporting Donor
Member
Oct 22, 2015
8,265
Tampa Bay Area
Pull and Examine your Air Filter and look for ANY compromised Un-Metered Air getting into the Air Intake System. Check the Air Piping and Flex Hosing leading up to the Clamps holding the Tubing on the Throttle Body for any alterations that look "Non-OEM" and re-fit them to being "STOCK-AS-A-CLOCK".

Any Modifications done outside of the OEM Design Intake Specs can often result in these weird events that happen only at certain RPM, Speeds, or Gearing...as in "The Case of a Bone Dry Transfer Case" or even a Bone Dry Rear Differential involving what Nikola Tesla called "The Power of Infinite Amplitude capable of destroying a New York High Rise Sky-Scraper Building....".

Take a Flashlight and examine the Transfer Case for any signs of Dirt collecting around "Wet" areas under there. If the Transfer Case is WET...it will prove to be almost Bone Dry Inside.

Here is a Video of this poorly designed Suspension Bridge (absent the correct Fencing or Drape side draping properly installed along the horizontal plane of a bridge borders) that eventually ...Shook the "Galloping Gerty" Tacoma-Narrows Bridge to pieces while reacting to the Ever Increasing Vibration Amplitude it experienced in a 40 MPH Lateral Wind that got "In Tune" with its super-structure:


All Intake Manifold systems that employ Resonators --- require --- that Special Device because the In-Coming inhalation of Air can --- Bounce off of the Pistons and Valves on their Intake Strokes and set up Hyper-Sonic Rebounds --- that MUST be absorbed, lest their "Harmonic Tune" level be reached and create Ungodly Noises when these high velocity sound waves cannot be dissipated from Internal Engine Components in the Rotating Assemblies.

The Two Part Harmonic Balancer bolted to the Crankshaft Nose is there for similar reasons...in order to absorb ---HORRENDOUS--- Longitudinal Vibrations that might destroy the Motor if allowed unlimited, Increasing Amplitude.

Unbalanced "Tire Hopping" is another example of hitting that precise Harmonic Sweet Spot that can make you wish your Mom never met your Dad... whenever on Long Drives while your Molars loosen up from experiencing this mostly preventable phenomena.

Once you hit that "Magic Sweet Spot" if these "Harmonics can get a "Toe-Hold" ...its Ever Increasing Amplitude can harm the engine internals and destroy the quality of the Driver's "Inner Ear" comfort zone.

The same can be said for Modified or Gutted Cat Systems and the use of Un-Tuned Headers or "Home Made Exhaust Systems" where a lack of appreciation of the --Real Problem Of Harmonics -- can eventually make driving ...One Total Misery.


PS... Watch Adam and Jamey on Myth-Busters showing WHY Marching Army Troops only cross Bridges in a "Broken Step" Fashion... versus using the ordinary Military "Marching In Lock Step" Pattern.

 
Last edited:

Mooseman

Moderator
Dec 4, 2011
26,103
Ottawa, ON
Just that maybe some of the other legit brands might be OK to use instead of AC Delco since half time you're not even getting the real thing...
From extensive experience here, it has been proven that only the ACDelco 41-103 work properly in this engine. Now this does not discount the possibility that the original manufacturer on these plugs, possibly NGK in the Iridium flavour, might also work properly.
 
  • Love
  • Like
Reactions: mrrsm and AC75TB07

AC75TB07

Original poster
Member
Aug 17, 2019
98
Canada
What exactly does "Iridium" mean in the grand scheme of spark plugs anyway?
 

mrrsm

Lifetime VIP Donor
Supporting Donor
Member
Oct 22, 2015
8,265
Tampa Bay Area
Sez So... Right in the WIKI... Iridium is the Second Densest form of Matter in the Universe. It is related to Platinum as a Rare Earth Metal that is Resistant to Oxidation in Sparking High Voltage conditions and in the presence of Extreme Atmospheres (such as in the 10+ to 1 Compression Ratio present inside of a 4.2L Engine's Cylinders ...over Billions and Billions of Rotation Cycles.

It is Resistant to Acids to the extent that the Caustic Chemicals present in Atomized Fuels being burned in an Oxygen Rich containment space that would dissolve ordinary Mild Steels and other Metals when exposed to such Harsh Operational Conditions. It's all there...Just.... RTFW.
 
  • Like
Reactions: AC75TB07

AC75TB07

Original poster
Member
Aug 17, 2019
98
Canada
Oh, I read it through but overall it sounds like the 4.2 is being a bit dramatic and should just calm down and stop being so extra 😂😁🤣
 
Dec 5, 2011
603
Central Pennsylvania
Oh, I read it through but overall it sounds like the 4.2 is being a bit dramatic and should just calm down and stop being so extra 😂😁🤣
PRACTICALLY...

The iridium tipped electrode on the specified spark plug resists erosion better than any other spark plug in this particular application to the point that it is expected to last 100,000 miles. Virtually every other spark plug tested in volume has been shown to fail due to electrode erosion or deposit build-up in less than the recommended service interval (100,000 miles). Many of the inferior plugs fail in less than 30,000 miles (in case you're wondering) in the case of non-iridium and non-platinum plugs.

The simple fact is that this engine is very hard on spark plugs and GM knew it, so they specified the toughest plug they could find and found one that lasts 100,000 miles (typically) when all specified maintenance is followed. At around 8 bucks a plug, it's a tad expensive to do them all... but when done every 100,000 miles, it's worth it.

Another thing to note, in the very old days one could clean spark plugs quite effectively with a purpose-built spark plug cleaner. It was a gizmo you'd hook up to an air-line and it would sand-blast the electrode clean - removing deposits, oils, etc and making it appear very close to brand new condition. This cannot be done with iridium plugs as the iridium tip, though exceptionally tough in doing its job, is also extremely brittle and can shatter or be knocked off if subjected to force of any description.

We're not even supposed to gap this plug, it comes gapped from the factory. If the gap looks off, replace the plug, period. Auto parts stores will swap out the plug if you bring a new one in that has a wrong gap.

Bad gaps on new plugs are indicative of either improper handling, or counterfeit plugs. These plugs are often subject to counterfeiting as they are very expensive so always verify the authenticity of individual plugs.
 
  • Like
Reactions: Mooseman
Dec 5, 2011
603
Central Pennsylvania
Sez So... Right in the WIKI... Iridium is the Second Densest form of Matter in the Universe.
Sorry, I have to point this out. This statement is preposterous as written. The second densest form of matter in the universe is a Neutron Star, second only to the core of a black hole.
Pure Iridium is the second densest element known to man, today. It is second only to Osmium.
Neutronium (neutron star core material) and black holes are many, many orders of magnitude denser than iridium and osmium.
 

mrrsm

Lifetime VIP Donor
Supporting Donor
Member
Oct 22, 2015
8,265
Tampa Bay Area
The "Preposterous" part worth pointing out... is the idea that what you suggested has any practical application ...to the Electrode "Tips" of Spark Plugs. :>)
 

Forum Statistics

Threads
23,721
Posts
642,586
Members
19,252
Latest member
Sheik480

Staff Online

Members Online