Noticeable Passenger Seat Vibration when using 87 Octane?

gen10_civics_ig

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I have an issue that is replicated 100% of the time, every time by following these steps:

Let's see if you guys have this problem or not.

2016 Civic EX-T - 30k Miles (but this issue started at around 20k miles) - Typically filled with 87 Octane except after an Oil Change where I would use 93 then gradually go back and stick to 87

- Turn on the engine, let it heat up to normal operating temp. (Does not matter if A/C is on or not)
- Drive up to a stop light or stop sign and engage the automatic brake hold
- Turn around and look at your unoccupied passenger seat. Mine starts vibrating back and forth like crazy, its very visible that the back of the seat is shaking back and forth.

I checked my engine mounts and they are still good. It is not an engine mount issue. This last tank I fuelled up with premium 93 and tried to recreate the steps, but noticed the seat doesn't vibrate nearly as much.

I am wondering if my fuel injectors have build up on them or if it is something else. However, I only fuel up at top tier name brand gas stations. Typically Shell and Chevron, so I do not know if I am grasping at straws here. What do you guys think? Took it to the dealer and they said its normal for it to do that, but I am not buying it.

Update: My tank of 93 octane is down to a 1/4 tank now and it is exhibiting the same behavior some of yall mentioned earlier, where it idles low around 600 rpm, and goes back up to 700 rpm when AC is on. Wasn't doing this before, but now it is. I wonder if Honda has a fix for this? I am still waiting to have time to try and clean the intake, and take it to dealer.





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gtman

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Funny you mentioned this. I get that every once in a while. Mostly after driving on the highway and then exiting. At the very first stop light the idle seems a bit rough. But it's fine after that. Doesn't matter what octane I use. Since it's only once in a while I just chalk it up as normal 1.5 turbo behavior. I have less than 6000 miles on my car.
 
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gen10_civics_ig

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Funny you mentioned this. I get that every once in a while. Mostly after driving on the highway and then exiting. At the very first stop light the idle seems a bit rough. But it's fine after that. Doesn't matter what octane I use. Since it's only once in a while I just chalk it up as normal 1.5 turbo behavior.
I wish it was once in a while for me. It is very consistent since I hit 20k miles, and the idle is noticeably rougher except when I am running premium. I do not want to run Premium every fuel up, however. But I am glad to have some feedback on this. I guess it is different for each car so far I am guessing.
 
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i was looking into the fuel types and grades. from my understanding, the higher grade octane has higher knock resistance.
per US News website, "
Simply stated, premium gas has a higher octane level than regular gasoline. The octane rating of gasoline determines how likely it is for engine combustion to occur at the wrong time. The higher the octane level, the less likely the combustion will occur at any time other than when it was designed to occur.

This mistimed explosion is known as “pre-ignition,” or an engine knock, simply because the sound resembles a knock or ping. Gasoline with a higher octane rating is designed to resist engine knock. Your vehicle may also emit lower-level pings when mistimed combustion occurs. An occasional ping or a knock is most likely not harmful to your vehicle, but frequent knocking can hasten the demise of your engine."

I'd stick with 91+.
 

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i was looking into the fuel types and grades. from my understanding, the higher grade octane has higher knock resistance.
per US News website, "
Simply stated, premium gas has a higher octane level than regular gasoline. The octane rating of gasoline determines how likely it is for engine combustion to occur at the wrong time. The higher the octane level, the less likely the combustion will occur at any time other than when it was designed to occur.

This mistimed explosion is known as “pre-ignition,” or an engine knock, simply because the sound resembles a knock or ping. Gasoline with a higher octane rating is designed to resist engine knock. Your vehicle may also emit lower-level pings when mistimed combustion occurs. An occasional ping or a knock is most likely not harmful to your vehicle, but frequent knocking can hasten the demise of your engine."

I'd stick with 91+.
Engine knock is something completely different though. That occurs under load, not at idle.
 
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hope you figure it out, the car behavior doesnt seem normal to me. its too new of a car to have this issue. dealers are shady and tend to waste customer's time to save themselves money. unfortunately, you'll have to be persistent in your complaint. If the dealer is being unreasonable and won't have techs look at your car. Or even if techs look and problems still persist. Then contact the next level, Corporate.

Seems like the variable in your testing is the fuel grade though. keep fuel at 93 and see what happens.
 
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dc2turbo

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It idles too low in gear on the CVT but if you have the a/c on will fix the problem. It doesn't matter what fuel you run
 

syncro87

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Our EX-T was exhibiting some roughness at idle. I shot half a can of CRC GDI Intake Valve cleaner in the intake while my wife kept the revs up. The idle is noticeably smoother now, like the car was when it was new.

I'm convinced it was some carbon buildup on the valves. 42k miles at the time I did this. I started to notice the rough idle around 30k. By the way, I'm the skeptical type. I held off on buying the CRC stuff for a long time because I figured it was snake oil. It is not. It works. I don't know how much deposit it removed, but it did something.

By the way, the Civic's intake tract makes it hard to spray the cleaner in there. Remove the rubber accordion between the air filter box and the plastic intake air tube. Shoot the cleaner directly in the long thin black plastic intake tube in small bursts. Take care not to lose the spray wand in the intake pipe. Longer bursts result in too much cleaner running out the intake, due to the way the intake is on the Civic. You can't follow the directions on the can exactly, or you'll lose half the cleaner on the ground. One or two second bursts. If you don't take the accordion boot off, you'll end up with a bunch of liquid in there, too. Take it out, get the wand as far into the plastic intake tube as possible, short spray bursts again and again of one or two seconds, pause 3 or 4 seconds, burst 1-2 sec, etc. If you have much liquid running out the tube end, you are using spray bursts that are too long, don't have the wand far enough into the tube, or don't have enough RPM sucking air in.

Side note: we have about 53,000 miles on two Civic turbos. 42k on one, 11k on the other. I have noticed no difference in performance in any respect when running premium fuel versus regular fuel, assuming both are 10% ethanol. I have noticed a small <5% improvement in MPG when running gasoline that does not contain ethanol, but no performance gain.
 

CivicXI

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Are u getting a full tank fresh every time?

Also, AFAIK, the engine won't continuously ping like crazy. What it does it dial back timing at the first sign of pinging so the rest of your drive is on a different map which shouldn't have any weird effects.
 

skstyle

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There have been many threads about this.

Your idle RPM is most likely at 620-ish (considered to be low) which is the symptom causing the vibrations. To remedy the vibrations, you can either turn the lowbeams on, OR turn the rear defroster on, OR turn the AC on, which will bump the RPM back up to 720-ish which would lessen the vibrations. The other way to remedy the vibrations is to get Hondata or Ktuner and bump up the idle RPM so you don't have to keep the lowbeams, rear defroster or the AC on all the time.

I've tried 87, 89, 91 and 93 octane on a fresh tank so it doesn't matter which fuel you use.

A few people I know have gotten Honda to change the engine mounts and it did nothing, the vibrations were still there.
 
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gen10_civics_ig

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hope you figure it out, the car behavior doesnt seem normal to me. its too new of a car to have this issue. dealers are shady and tend to waste customer's time to save themselves money. unfortunately, you'll have to be persistent in your complaint. If the dealer is being unreasonable and won't have techs look at your car. Or even if techs look and problems still persist. Then contact the next level, Corporate.

Seems like the variable in your testing is the fuel grade though. keep fuel at 93 and see what happens.
I found a dealer today that is willing to cooperate after I reinstall my stock muffler which I am going to do even though it is not the cause of the issue, because I had it happen before my muffler delete. Wish me luck!

It idles too low in gear on the CVT but if you have the a/c on will fix the problem. It doesn't matter what fuel you run
There have been many threads about this.

Your idle RPM is most likely at 620-ish (considered to be low) which is the symptom causing the vibrations. To remedy the vibrations, you can either turn the lowbeams on, OR turn the rear defroster on, OR turn the AC on, which will bump the RPM back up to 720-ish which would lessen the vibrations. The other way to remedy the vibrations is to get Hondata or Ktuner and bump up the idle RPM so you don't have to keep the lowbeams, rear defroster or the AC on all the time.

I've tried 87, 89, 91 and 93 octane on a fresh tank so it doesn't matter which fuel you use.

A few people I know have gotten Honda to change the engine mounts and it did nothing, the vibrations were still there.
I read about those issues, however after many repeated observations, the higher octane fuel is actually making a difference in the severity of the vibration. Just to make sure I was not imagining it, I went and tried it again a few minutes ago with the 93 in my tank and the passenger seat doesnt look like it's having a seizure anymore. I tried turning A/C on and off and it makes no difference. Only thing that clearly triggers it is 87 in the tank, normal operating temperature, braked in D. However, I do notice the idle is lower than it should be when I was running 87, so I think you guys are right about that. It idles higher with 93. Why? I have no idea, I am just observing this behavior.

Our EX-T was exhibiting some roughness at idle. I shot half a can of CRC GDI Intake Valve cleaner in the intake while my wife kept the revs up. The idle is noticeably smoother now, like the car was when it was new.

I'm convinced it was some carbon buildup on the valves. 42k miles at the time I did this. I started to notice the rough idle around 30k. By the way, I'm the skeptical type. I held off on buying the CRC stuff for a long time because I figured it was snake oil. It is not. It works. I don't know how much deposit it removed, but it did something.

By the way, the Civic's intake tract makes it hard to spray the cleaner in there. Remove the rubber accordion between the air filter box and the plastic intake air tube. Shoot the cleaner directly in the long thin black plastic intake tube in small bursts. Take care not to lose the spray wand in the intake pipe. Longer bursts result in too much cleaner running out the intake, due to the way the intake is on the Civic. You can't follow the directions on the can exactly, or you'll lose half the cleaner on the ground. One or two second bursts. If you don't take the accordion boot off, you'll end up with a bunch of liquid in there, too. Take it out, get the wand as far into the plastic intake tube as possible, short spray bursts again and again of one or two seconds, pause 3 or 4 seconds, burst 1-2 sec, etc. If you have much liquid running out the tube end, you are using spray bursts that are too long, don't have the wand far enough into the tube, or don't have enough RPM sucking air in.

Side note: we have about 53,000 miles on two Civic turbos. 42k on one, 11k on the other. I have noticed no difference in performance in any respect when running premium fuel versus regular fuel, assuming both are 10% ethanol. I have noticed a small <5% improvement in MPG when running gasoline that does not contain ethanol, but no performance gain.
This sounds like it could be the problem. Thank you for the detailed write up, makes me confident I can clean out the intake myself. Will give that a shot and see what happens!

Are u getting a full tank fresh every time?

Also, AFAIK, the engine won't continuously ping like crazy. What it does it dial back timing at the first sign of pinging so the rest of your drive is on a different map which shouldn't have any weird effects.
Yeah, I run my tank low and fill up to the top each time.
 

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Again, I've had this issue on my 18 Sport Hatch before. Ever since I bought my new car, I've tried 87, 89, 91 at ARCO. At around 1K Miles, I noticed the vibrations. I decided to try Shell 91 and the vibrations suddenly stopped. Also tried Mobil, Chevron and still no vibrations. So it MIGHT be the fuel brand you use.
 
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gen10_civics_ig

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Again, I've had this issue on my 18 Sport Hatch before. Ever since I bought my new car, I've tried 87, 89, 91 at ARCO. At around 1K Miles, I noticed the vibrations. I decided to try Shell 91 and the vibrations suddenly stopped. Also tried Mobil, Chevron and still no vibrations. So it MIGHT be the fuel brand you use.
Gonna keep experimenting with fuel octanes and different top tier gas stations and see what happens. Thank you!
 

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