[SLK]

Originally Posted by amit_mechengg

get your valve tappet clearances checked.

Originally Posted by tsk1979

check the timing if Fuel is not the culprit. This is the most common cause.

thats it.... do those 2 things and you are done.

getting MASS to do these things specially on your request is another story!...

normally after services and injector cleaning... my car (wagonR) starts to knock....

[rks]

Originally Posted by ScarySkulls

Car:- Constant knocking whenever accelerator is depressed. Especially after 80. Car doesnt knock much when not fully warmed up. But starts doing it after a few kilometres.

Car was serviced one month ago. Injectors were cleaned.
Any possible causes?

P.S.>> When I drive alone, knocking is reduced. But goes up to alarming levels when friends/family travelling alongwith.

So your car knocks when engine is warmed up, and when under load. Is your AC on? Did you try switching off the AC? One possible reason for knocking could be that your engine is getting overheated due to improper cooling. Check the cooing system.

Also as noted by you and SLK, the engine seems to knock after a service. This is surprising. Only reason I can think of is that the ECU may be getting reset at service and not doing its job correctly. Note that air filter will be either cleaned or replaced during a service. So the car may be running a lean mixture due to either faulty ECU or some blockage in the fuel flow.

[ScarySkulls]

Originally Posted by rks

Is your AC on? Did you try switching off the AC?

Yes. Tried both ways. Knocking persists.

Originally Posted by rks

Also as noted by you and SLK, the engine seems to knock after a service. This is surprising.

The service was done a month or two ago. I dont think a bad service job will have effects showing up so late.

Originally Posted by rks

Only reason I can think of is that the ECU may be getting reset at service and not doing its job correctly.

No battery terminal was removed to effect an ECU re-set. Even in case it did somehow, for reasons not known to me, the engine shouldn't still be knocking on the base default maps.

Originally Posted by rks

Note that air filter will be either cleaned or replaced during a service.

Correct Sir. It was cleaned this time and put back as a visual inspection told that there was still some life left in it.

Originally Posted by rks

So the car may be running a lean mixture due to either faulty ECU or some blockage in the fuel flow.

Will get it checked for any error codes in that case, whenever I go towards that part of town where the service station is located.


I think all this is more of an adulterated fuel drama. What say?

[Jaggu]

Yup adulterated fuel drama can be this, but check your air filter, fuel filter, plugs etc anyways maybe at service it was overlooked, you never know.

[ScarySkulls]

Originally Posted by Jaggu

Yup adulterated fuel drama can be this, but check your air filter, fuel filter, plugs etc anyways maybe at service it was overlooked, you never know.

Air filter, spark plugs cleaned before my eyes. Fuel Filter is brand new.
thanks anyways, Jaggu.

I'll observe this tankful and see what happens after the next fuel up.
Will get back to you guys.

[Jaggu]

Hope the plug have enough left in them also? Plugs sometimes can cause havoc. Also plug wire, breakages due to incorrect push and pull on them are quite common.

Ol story again: Once in an 800, one of the plugs had the ceramic surround on the tip which broke free. So when we visually checked it (holding the tip up) everything was fine. Plug cleaned and put back, pinging again.

Finally a workshop kid took it and shook it to see if something was broken, and behold the ceramic surround had come loose and resting on the tip (noticeable only when the plug is help with tip facing down).

[AMATMO]

its quite common in many cars after 1 lac mark
and a normal solution would be to check the fuel ffilter ,air filter and the spark plugs should function well

[ScarySkulls]

Originally Posted by Jaggu

Hope the plug have enough left in them also? Plugs sometimes can cause havoc.

What is the average life of a plug? Mine have done 15k by now.

Originally Posted by Jaggu

Also plug wire, breakages due to incorrect push and pull on them are quite common.

will check for these. But how do they result in knocking on anything more than 30% throttle? OR Med-high RPMs?

Originally Posted by Jaggu

Ol story again: Once in an 800, one of the plugs had the ceramic surround on the tip which broke free. So when we visually checked it (holding the tip up) everything was fine. Plug cleaned and put back, pinging again.

Finally a workshop kid took it and shook it to see if something was broken, and behold the ceramic surround had come loose and resting on the tip (noticeable only when the plug is help with tip facing down).

Very interesting!! Must check plugs for sure.

Originally Posted by AMATMO

its quite common in many cars after 1 lac mark
and a normal solution would be to check the fuel ffilter ,air filter and the spark plugs should function well

Yes Sir. Car should be crossing 1lac mark 6-7 years down the line. Will keep those points in mind.

[Jaggu]

Plugs can last between 10-20 k normally and can pull through to 40 k in some extreme cases Ideally replace plugs at 10k since alto OE plugs are just plain cheap to buy, and the hassle not worth having. If its better and pricey stuff like NGK 15 to 20 k mark is good time to change.

A simple cut in plug wire might be felt only at higher rpms, when the spark starts to arc/leak through the break. This is just one of the case, but there are many similar situation and hence check the wires. Its 10 mts job.

[swift8847]

Why exactly does knocking occur? And how is it noticed in the engine? Is there some detailed explaination on the forum? I tried searching, but could not find. If there is a some info on this can someone guide me to that thread.

[SLK]

Originally Posted by swift8847

Why exactly does knocking occur? And how is it noticed in the engine? Is there some detailed explaination on the forum? I tried searching, but could not find. If there is a some info on this can someone guide me to that thread.

see this link OmegaMotors.com - The Truth About Gasoline

it was on the forum itself!... in some OLD topic started by me on my WagonR knocking... http://www.team-bhp.com/forum/techni...-knocking.html

[vaasu]

Originally Posted by ScarySkulls

What is the average life of a plug? Mine have done 15k by now.




will check for these. But how do they result in knocking on anything more than 30% throttle? OR Med-high RPMs?




Very interesting!! Must check plugs for sure.



Yes Sir. Car should be crossing 1lac mark 6-7 years down the line. Will keep those points in mind.

ScarySkulls:
Any updates on the problem?

[abhibh]

any updates ???????????

[ScarySkulls]

Have been using normal fuel since the past month and observing the car.
Don't think the car is knocking anymore in the city.
Now waiting for a proper highway drive. Lets see....

[alpha1]

Originally Posted by sukheshkumar

I think it is Premium Petrol which is the reason for this knocking.

IMPOSSIBLE.
Higher octane MEANS a fuel that causes less knocking.

Earlier, sulphur was added as an additive to induce anti knocking properties.

SULFUR has NEVER been ADDED to petrol.

With the advent of Green marketing, the same additive is considered as an impurity and premium gasolenes take this out of Gasolene.

Lets get to the basics - Refining 101.
Crude oil gets refined into LPG, Naptha, Kerosene, Diesel, Vaccum Gas Oil, and Residue.

This Vaccum gas oil gets cracked and makes LPG and Gasoline (and other crap).

Now the content of sulfur in Gaoline depends on two things - 1. sulfur content in Crude. More sulfur in crude - also called Sour crude - the more the sulfur in Gasoline.
2. Treatment - Hydrotreating usually - this reduces the sulfur content in Gasoline.

So there goes your theory of Sulfur being additive.

Reduction of knocking is done by car makers. I do not know whether alto manual prescribes Premium Gasolene. Check this aspect.

This knocking is not heard in cities and are heard only on Highways because of ambient noise in the city.

Sukhesh Kumar BR

Octane number requirement is dependent on engine - mainly on compression ratio and RPM basis.
Engines running on high CR and at high RPM - in general - require higher octane fuel - or they will start knocking badly.

Engines that don't have high compression or dont run at high RPM, dont need high octane because they dont operate at conditions that cause knocking.

HOWEVER, if you fill such engines with high octane fuel, it would NEVER cause any knocking. Simply because you are feeding an over spec fuel.