Fuel Knock??

**rsscertified** · February 1st, 2009 06:50 PM

hello po - ask ko lang if you also experience this on an automatic car, 1st gear and moving tapos hard press sa gas pedal to accelerate, meron light knock. Pero, kapag smooth press sa gas pedal wala naman knock na maririning.

I asked this kasi yesterday, kasi naririnig ko un kapag ginagawa ko ung hard press. Di ko naman ginagawa un talaga on a regular basis napansin ko lang nung one time kailangan ko lang magaccelerate ng mabilis. i'm using Petron Xtra unleaded (93+ Octane), 3 weeks ago po 10km checkup po nung car, napalitan po ung spark plugs, oil filter, change oil. Last last saturday, nagpakarga po ako ng XCS (95 octane), naririnig ko pa din po ung light knock. From the altis manual, dapat daw di ikabahala ung light knock. Kung heavy knock daw po eh dalhin na sa toyota dealer.

Yesterday also pina-road test ko po ung car. For some strange reason eh wala kaming narinig na knock, pinatakbo nya sa alabang ung car, umabot ng 130km wala po, very smooth.

Ask ko po opinions nyo mga experts, additional knowledge na din for me. Also, need ko nga ba ipacheck pa ito ng todo? May kinalaman po ba un sa pag press sa pedal?

Thanks po in advance

**v6dreamer** · February 2nd, 2009 03:36 AM

Hopefully, it just about the octane gas are you using. Look in your owners manual and only use the proper octane.

But what you are describing sounds like one of the following; collapsed lifter, worn camshaft, excessive gap in the lower end (rod) bearing. If it has timing chain - that could be yet another source of this type of noise. The good news is if: it's still under warranty, if not $$$$. Go to the dealer(casa) and don't leave until they fix it because noise is minor, they'll start telling you that nothing is wrong hoping that the engine explodes right after the warranty is expired.

**rsscertified** · February 2nd, 2009 07:42 AM

Originally Posted by v6dreamer

Hopefully, it just about the octane gas are you using. Look in your owners manual and only use the proper octane.

But what you are describing sounds like one of the following; collapsed lifter, worn camshaft, excessive gap in the lower end (rod) bearing. If it has timing chain - that could be yet another source of this type of noise. The good news is if: it's still under warranty, if not $$$$. Go to the dealer(casa) and don't leave until they fix it because noise is minor, they'll start telling you that nothing is wrong hoping that the engine explodes right after the warranty is expired.

Hi V6dreamer, thanks for your response. I'm really new on cars, so - collapsed lifter/worn camshaft etc I really don't know about those.

Yes this is still under warranty. 1 year pa lang po ito. Actually they have advised me to empty the gas tank before filling it up again then check if the noise is still there.

According po sa manual, 91 octane or higher is recommended. Since I got it, I'm using xtra unleaded from Petron which is 93+ octane. just recently I used XCS since they said it's much better for mileage.

This morning, while I drive to office, I'm trying to check kung merong noise pa din, binalik ko sa smooth press sa pedal ng gas, seems to be fine naman. baka na sa pag biglang apak ng gas medyo may light knock.

**v6dreamer** · February 2nd, 2009 10:03 AM

What is XCS?
Proper maintenance in your car is always your best bet of better milage and they way you drive....nothing else. The rest......use at your own risk.

**niky** · February 2nd, 2009 10:13 AM

Might have been bum gas.

No brand new car should knock on sudden prods of the throttle. With electronic fuel injection and O2 sensor mediated fuel trimming, it's next to impossible.

**rsscertified** · February 2nd, 2009 12:07 PM

Originally Posted by v6dreamer

What is XCS?
Proper maintenance in your car is always your best bet of better milage and they way you drive....nothing else. The rest......use at your own risk.

Hi V6Dreamer, it's a name for unleaded gas here in Manila that has 95 RON
http://www.petron.com/fueljourneys/f...fuels-pxcs.asp

Originally Posted by niky

Might have been bum gas.

No brand new car should knock on sudden prods of the throttle. With electronic fuel injection and O2 sensor mediated fuel trimming, it's next to impossible.

Hi Niky - thanks for your response. May I ask - what do you mean with bum gas? I apologize, I'm really new with engines.. What should I do? Do I need to change to a new fuel? Thanks!

**normanenoza** · February 2nd, 2009 07:56 PM

did they check if ok pa yung knock sensor mo. a busted knock sensor will never trigger the check engine light. IMHO, using gas with higher octane rating than the recommended is just a waste of money. remember this, it is already the recommended gas specified in the manual and not the minimum required. your engine will just utilize the same amount of heat irregardless of the octane rating of the gas.

**rsscertified** · February 3rd, 2009 08:40 AM

Originally Posted by normanenoza

did they check if ok pa yung knock sensor mo. a busted knock sensor will never trigger the check engine light. IMHO, using gas with higher octane rating than the recommended is just a waste of money. remember this, it is already the recommended gas specified in the manual and not the minimum required. your engine will just utilize the same amount of heat irregardless of the octane rating of the gas.

hi normanenoza, thanks for your reply - sir where can I check the knock sensor? altis po tsikot ko. inuubos ko na lang ung tank ko and will go back to xtra unleaded.

**bratski** · February 3rd, 2009 10:50 AM

rss
i had the exact same problem as yours a few weeks ago, although innova gas matic yung sa akin, but the fuel i use is also petron extra unleaded. nagkakaron din ng knocking under hard acceleration but under normal circumstances wala naman. i changed sparkplugs, fuel filter(grabe ang mahal nito), cleaned the maf sensor, o2 sensor. ganun parin. so i tried switching to xcs(higher octane) and still ganun parin. pina check ko sa friend ko na may talyer and what he did is binaba fuel tank and empty its contents and replaced with petron blaze(96 octane), cleaned my injectors, ayun nawala na knocking even under hard acceleration and uphill climbs. turns out hindi ata compatible yung unleaded and xcs ng petron sa ride ko. my manual also recommends a minimum of 91 octane pero ang extra unleaded is 93 octane na. so what gives? ang mahal pa naman ng blaze and hindi naman high performance ang innova to use that fuel. imo burning money lang ako sa ganitong situation and im looking to change to caltex or shell.

**bratski** · February 3rd, 2009 11:08 AM

Originally Posted by rsscertified

hi normanenoza, thanks for your reply - sir where can I check the knock sensor? altis po tsikot ko. inuubos ko na lang ung tank ko and will go back to xtra unleaded.

knock sensors are usually located on the engine block near the intake manifold, to check if its working get a wrench or some hard object and lightly knock on the area near the knock sensor (not on the sensor itself,with the engine idling), you will notice na may magbabago sa timing mo, the sensor will retard timing if it senses knock (assuming working nga yung sensor, it it doesn't, probably sira).if sira knock sensor, you have to replace it($$$) pero mahirap ma sense kung nag iba nga yung timing if wala kang timing light. your best bet would be to empty your tank and try other fuels. minsan compatibility issue ito. ako i learned it the hard(expensive) way.