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Discussion Starter #1
I filled up 93 at different gas station and it make a knocking sound however, when I filled up Shell 93 it won’t make any of that sound. Do I have dirty spark plugs?


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I filled up 93 at different gas station and it make a knocking sound however, when I filled up Shell 93 it won’t make any of that sound. Do I have dirty spark plugs?
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Because SHELL premium gas works best on the 2nd gen MDX IMHO! :29:
<center><img src="https://1t0hgcvckoj1j7wc82ddqko1-wpengine.netdna-ssl.com/wp-content/uploads/Shell-VPower-Nitro-Plus-Best-Engine-Protection-You-Can-Get-Premium-Gas-Gasoline-93-octane.jpeg"></center>

If you want to increase the chance of hearing knocking sounds and/or want to potentially see the 'CHECK EMISSION' light appear, then regularly get gas for your 2011 MDX here:
<center><img src="https://www.bp.com/content/bp-country/en_au/australia/products-services/service-stations/own-service-station/jcr:content/article_dropzone/article_dropzone/carousel/image1.img.840.high.jpg/1395865790713.jpg"></center>
 

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Discussion Starter #3
Forget to mention this.
1. When the engine is COLD ( like in the morning) it doesn’t make the knocking/metallic grinding during light/hard acceleration.
2. When the engine is WARM (light stop and restart the car 30 min to 3 hours later) it makes the knocking/metallic grinding during light/hard acceleration.
3. When the engine is HOT (normal operating temp) it doesn’t make the knocking/metallic grinding during light/hard acceleration.

Some people said it like a bad torque converter, dirty fuel injector, and etc. Maybe the problem is not having to with the gas at all. Maybe I have a much bigger issue with the transmission torque converter. One guy one online had the same issue like mine and the dealer replaced the torque converter and he said the problem went away.

Here is the link that these MDX owners have similar problems like mines https://forums.edmunds.com/discussion/13249/acura/mdx/mdx-engine-knock-sound





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Mine takes whatever it’s given without problem - though always Premium. It’s about 90% Costco & the rest Fred Meyer or Safeway
 

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Gas is a very subjective topic. Personally, I stick with the name brands except for BP & Mobile. For some reason, the quality is not consistent with BP franchises near me and I don't like either of their corporate policies. Costco & SAMS's club are good, too.

There are several factors that can cause knocking or pinging, but the simplest explanation is typically not getting the adverised octane rating on the pump. I'm not a fan of Ethanol mixes but it shouldn't be an issue (<10%) with our vehicles.

Try different stations to narrow down if it's the vehicle or the station. There's good advice on the forum if it turns to be the vehicle.

That's my $0.02
 

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Do you mostly get gas from the same station just in different locations? Do you have to fill up at random places because of your daily travels? I've always had pretty good luck with 91 Octane Sam's Club or Costco gas at home and when I travel cross country. I haven't noticed an issue when I do have use other brands if Sam's or Costco isn't available. It is usually not more than 3/4 of tank before I hit another Sam/Costco down the road.

93 Octane is suppose to be more anti-knock compared to reg or mid grade fuels? Have you tried going with just a 91 Octane with less ethanol? Maybe the MDX is having to adjust too much since 91 Octane suppose to be the sweet spot for performance/mpgs?
 

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Do you have the issue of burning oil? Maybe you have a cylinder(s) with some oily build-up causing the knocking with certain fuels? Won't know until you start to pull the plugs.
 

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your Spark Plugs aren't even a year old yet! :surprise: perhaps bad product and/or installed improperly?!
https://www.mdxers.org/forums/74-second-generation-mdx-2007-2013/154866-should-i-replace-spark-plugs-use-sea-foam-get-rid-engine-ticking-5.html

11-24-2017, 06:06 PM
New spark plugs are here and they are GENUINE, $9.60 each compares to $15 @ AutoZone.

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That is weird, I have been using basically all brands here in Baja: National "PEMEX" and now since they entered the business Chevron Gas, BP and ARCO and they all seem to work just fine on my MDX none of them feel superior to the other and there is no knocking sound with either of those...

They are all supposedly 92octane which is the standard for premium here in México.
I now prefer to fill up in BP Gas Stations since they seem to rip you off the least (Fill you up less than what you paid for).
 

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Discussion Starter #11
Do you have the issue of burning oil? Maybe you have a cylinder(s) with some oily build-up causing the knocking with certain fuels? Won't know until you start to pull the plugs.


Yes the car is having issue with burning oil.
That is what I am thinking...oily build up on the piston AND spark plugs. Another phenomenon is that the knocking only happens during a WARM start and continue knocking for about 1-5 minutes during normal acceleration. Once the engine reaches its normal operation temp the knocking went away. It could be that the oily pistons/spark plugs get burn off when the engine reaches it normal operating temp and it doesn’t cause the knocking? I remember when I changed my spark plugs about a year ago I noticed the old spark plugs were oily but not much. Back then I have the same issue with knocking and after I replaced the spark plugs the knocking was gone. And now it is coming back. Maybe I need change the spark plugs again just to find out.
What is the best way to clean carbon or oily build up on the spark plugs? I want to reuse the plugs because they are about a year old and have about 26k miles on them.




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I haven't heard of the oil burning issues being so severe than the spark plug will foul..
Are you certain you dont have another problem? probably Injector or Valve related?

When was the last time the valves were adjusted?
 

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Discussion Starter #13
I haven't heard of the oil burning issues being so severe than the spark plug will foul..

Are you certain you dont have another problem? probably Injector or Valve related?



When was the last time the valves were adjusted?


I really don’t know. What really puzzle me is that the knocking only occurs when the engine is started up from WARM and went away after 5 minutes or so after the engine reaches it normal operating temp.


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Discussion Starter #16
Metal expands if you have a bad valve adjustment it can coat the valves on carbon build up as you have un-even burning from a leak.



If you don´t know when was the last time the valves were adjusted at 200K? It might be way long overdue, I would start with that. Here is my DIY to adjust valves: https://www.mdxers.org/forums/74-second-generation-mdx-2007-2013/156393-diy-adjusting-valves-acura-mdx.html


I adjusted the valve when I replaced the camshaft, remember? About a year ago. I am kind of concern the knocking will do harmful to the engine.


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It all depends on the type of knocking you are hearing… Pre-Ignition Knocking is the harmful one... But un-even combustion can also sound like knocking.
 

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Discussion Starter #18
It all depends on the type of knocking you are hearing… Pre-Ignition Knocking is the harmful one... But un-even combustion can also sound like knocking.


It sounds like I have a combustion before the any of the spark plugs ignited because the oily plugs delay the ignition. Does that sound right?


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Yeah but even then you could only have missfires, There is nothing allowing pre-ignition condition so there should be no pre-ignition knocking at the very most it could only missfire due to the fouled plug.
 

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It's most likely not the gas you are using that is causing the problem.
 
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