Yaris vibration abnormality

[talhahs]

Scenario : I have noticed the vibration of my Yaris has increased just recently when i mistakenly fueled it up with petrol 95 (super premium 95), i was using petrol 91 since i purchased it. Though, this vibration has gone down gradually after i first started using 95.

Details : When in Neutral, it vibrates very little but as i press softly the accelerator, it loses its vibration. When in Drive mode, it vibrates if it is stationary and as soon as i take off, it loses its vibration. Is this in anyway linked to my engine mount problem??

Because before purchasing this pre-owned car, i took it for computer test and was diagnosed problem with right engine mount...i never took it to mechanic since i am not hearing any sound or noticed any problem yet...Any advise?

[YarisSedan]

Do not use high octane gas in a low compression engine. Causes incomplete combustion which in turn is loss in fuel economy and excessive carbon build up and i mean excessive on top of your pistons and on your valves and cake them up especially the egr system. It can cause rough running and missfiring if used over long period of time.

It can get bad enough of a layer on the of the piston that might even effect compression ratio.

At this point you could try several treatments of seafoam to try to clean out the carbon i would try some through the intake and then changing oil afterwards, and then some through the fuel tank.

[talhahs]

As far as the fuel economy is concerned, premium 95 is going good uptil now. I have done 467 km with still 3/8 bars remaining on my fuel gauge.I believe my car would do 500 km on 91 with full tank. Although, i never ran it dry and used to refuel before reaching the flashing bar..

[YarisSedan]

Well what im trying to get at is that you are spending extra money to cause damage and efficiency to your vehicle. A lower octance gas burns quicker which means more power and efficiency. Higher ocane on a low compression engine burns slower which means you wont be able to burn all the fuel. Maybe as much as 25 percent is lost and wasted. Partially burn fuel brakes down to carbon which is most likely the cause of all your problems.

Unless your vehicle is turbocharged you dont need such a high octane gas. If you run a low octane gas and your car starts to ping or runs worse that means you have so much carbon caked on your pistons its actually changed your compression ratio now. Which was actually caused/created by running high octane for so long.

[CTScott]

One of my Yaris did the vibration (which was due to the RPM dropping) while stopped thing and I actually found it to be a partial vacuum leak at the brake booster (it only leaked with the brake fully pressed).

If I pulled the ebrake lever while it was vibrating and took my foot off the brake it would stop vibrating. I picked up a brake booster from a junk yard and replaced mine and the vibration went away.

[talhahs]

Thanks a lot YarisSedan, I shall move back to 91 once I dry up my fuel tank to last bar. Its only been a week on 95, I hope it has not destroyed my engine yet. I will need a refuel hopefully this week. I will not want to go for thorough cleanup as you said earlier (unnecessary costs!)..Any suggestions?

Secondly, about the engine mount problem? How crucial is that and what are its symptoms? How can I get my car to proof that it has engine mount problem?

[CTScott]

Originally Posted by talhahs

Thanks a lot YarisSedan, I shall move back to 91 once I dry up my fuel tank to last bar. Its only been a week on 95, I hope it has not destroyed my engine yet. I will need a refuel hopefully this week. I will not want to go for thorough cleanup as you said earlier (unnecessary costs!)..Any suggestions?

Secondly, about the engine mount problem? How crucial is that and what are its symptoms? How can I get my car to proof that it has engine mount problem?

It is actually a myth that using a higher octane fuel than a manufacturer specifies will cause issues. It will not help anything (some people use higher octane thinking they will see an increase in power or fuel efficiency), but it will not result in more carbon deposits.

Carbon deposits are formed naturally with the combustion of gasoline. Fuel additives are the key to reducing carbon deposits. Using gasoline with Polybutene Amine (PBA) as an additive will result in more carbon than gas with Polyether Amine (PEA) as the additive. Lower grade fuels (not lower octane, but poorer quality fuels) use the cheaper additives and typically have a lower concentration of the additives.


As for the right engine mount; That one is a hydraulic damper and if it ruptures it will lose its ability to damper the engine vibrations. Check for rips in the rubber jacket or evidence that fluid leaked from it. You can also grab the engine block and wiggle it against the mount. It should move freely, but with significant resistance.

[Kaotic Lazagna]

I use the highest octane (premium, 91 here; regular is 87) once a month or two since it has a higher concentrate of detergent of the gas brand that I use (Chevron) for cleaning purposes. I see, and didn't expect, a boost in power. I do, however get WORSE gas mileage when I use premium.

[Kaotic Lazagna]

http://www.youtube.com/watch?v=gQghB4asSnI

[YarisSedan]

Originally Posted by Kaotic Lazagna

I use the highest octane (premium, 91 here; regular is 87) once a month or two since it has a higher concentrate of detergent of the gas brand that I use (Chevron) for cleaning purposes. I see, and didn't expect, a boost in power. I do, however get WORSE gas mileage when I use premium.

Its a common misconception, a lot of people do use premium once and awhile for the same reasoning but there is no additional additives in premium gas then you get with regular gas. Its better to just stop by your local parts store and buy a bottle of chevron techron fuel injector cleaner and adding that to your gas tank. A lot of times they are on sale and for a few dollars which is what your are going to be spending on 91 octane anyways

As long as you use a top tier gas you should be fine

http://www.toptiergas.com/

Ive recently switched from chevron back to 76 gas they have 3 times the amount detergant additives of the minimum required by the EPA and 30 percent more than the top tier standard

[Kaotic Lazagna]

Originally Posted by YarisSedan

Its a common misconception, a lot of people do use premium once and awhile for the same reasoning but there is no additional additives in premium gas then you get with regular gas. Its better to just stop by your local parts store and buy a bottle of chevron techron fuel injector cleaner and adding that to your gas tank. A lot of times they are on sale and for a few dollars which is what your are going to be spending on 91 octane anyways

As long as you use a top tier gas you should be fine

http://www.toptiergas.com/

Ive recently switched from chevron back to 76 gas they have 3 times the amount detergant additives of the minimum required by the EPA and 30 percent more than the top tier standard

I think every website I read about premium's detergent levels say it has more. Here is one, http://money.msn.com/saving-money-ti...a-b30bf27a090f. But I don't recall any of them saying how much more. So if it's a miniscule amount, which is still technically "more," I'm just losing out since premium costs more and I get worse gas mileage for some reason Oh, and I will only try to get 91 if the price difference is around 20 cents from 87.

I also thought about just using Techron Concentrate Plus more often, but I also read that it's not recommended to use often

But yeah, I use nothing but Chevron for my Yaris, and the other two cars I had in the past.

[YarisSedan]

I don't know about that article "Using regular-grade fuel in a vehicle designed for premium
Can you do it? Absolutely. Most people should, " once the engine detects a knock it will retard the timing which will reduce economy and power. Reduction in power and economy = less MPG which negates any money you saved.

I could be wrong though about premium gas containing more fuel additives but if they are more it cant be by much. I have seen engines taken apart that have been running only discount gas such as rotton robbie, costco ect and have horrid amount of carbon build up on top of the pistons that needed to be scraped off when going back together. And then engines taken apart that have been running strictly chevron for example and the layer of carbon was so thin. I ran a can of seamfoam in a customers car that had 140k miles and only a puff of smoke came out and that was it. I was shocked expecting there to be tons of carbon coming out however there was none, Another car that had only 40k miles the smoke was so horrible it blew past the shop and down the street and actually stopped traffic, it was so bad the car stalled and and we couldn't get back started again for awile and when we did more smoke filled the street and neighboring areas and we had to take it on the freeway at high rpm for awhile to try to blow it out when it got back to the shop it smoked for a good 30 minutes still. Needless to say the customer used only discount gas so i believe there is a big truth to top tier gas from personal experience.

[jcboy]

i dont know about carbon build up, but definitely premium gas gives more power and worse mileage. (personal experience with a Civic Vtec engine and this Yaris VVTi engine i have now)

vibration on idle and on D meant a dirty MAP sensor on the civic, which would mean a dirty IM (intake manifold). cleaning both costs a measly $10-15 here in Manila, would drive that away.

check your idle if it is going down beyond normal or is erratic, if so it might mean a dirty manifold/sensor--and yes a possible vacuum leak too (but probably not on a 5 year old yaris).

oh yeah, it helps to redline the car every now and then. i kept my civic for 16 years that way and sold it like new and the engine (with the new owner now) has never been rebuilt, nor the head been taken down.

[why?]

wow, exxonmobil finally made the top teir list. Have they changed their standards or did mobil change their gas?

I am surprised BP is not on the list. When I was able to fill up with BP, I was able to get the best gas mileage.