- Hey, how's it going there, Sulferers.
Today we're gonna talk about what is engine knock,
and how you can easily fix it.
Now to be clear,
this video is going to be
on how you can diagnose and fix engine knock,
also known as spark knock,
caused by detonation,
which is very different a rod knock or a main bearing knock,
which is caused by worn out or damaged bearings
at your main or connecting rod journals on your crank shaft.
However, both types of knocks make it very similar
knocking, or clacking, or tapping noise,
so it's very important you know how to differentiate
and properly diagnose your issue.
And that's exactly what we're gonna do today
on this 2004 Ford Ranger,
which we will leave as a knocking noise due to detonation.
Now this car has a 3.0 Leader V6 Engine,
but you can use the diagnostic procedures in this video
on any car, year, make, and model.
All right, so first let's talk about
what is the detonation,
and how it causes that knocking sound you hear
whenever it occurs.
So here's our cylinder head,
it obviously usually lays on top our engine this way.
And here's our valves.
Here's our spark plug.
And detonation is basically whenever
you have a second ignition of the air/fuel mixture
inside your combustion chamber
after your computer has fired your spark plug.
So we'll use this cylinder as an example,
and assume that this piston
is coming up on its compression stroke.
So a few degrees before it reaches top dead center,
as it's normal,
our computer commands the ignition coil to fire a spark
at our spark plug.
As that happens, we ignite the air/fuel mixture
that's in our combustion chamber.
But as soon we ignite the air/fuel mixture
with our spark plug,
a second, or maybe even a third combustion or ignition
of the air/fuel mixtures
inside our combustion chamber occurs,
maybe due to excessive heat,
or extreme pressure inside our combustion chamber,
and as the ignition from the second or third combustion
reaches the ignition from our spark plug,
and as they collide,
that's what makes that distinct knocking noise
that comes from your engine.
All right, so there's the explanation
for what denotation is.
And again, what usually causes detonation
is either excessive and/or pressure
inside your combustion chamber.
So now let's talk about what are the most common things
that could cause one of these,
and cause detonation with your engine.
All right, so in my opinion,
the most common cause of detonation that people experience
is putting the low octane fuel,
basically the wrong fuel in their car.
And this happens a lot with higher-end vehicles,
let's say, like a Mercedes,
where the engine is rated for,
let's say, a 91 octane fuel,
but people go to the gas station,
the lower octane fuel is obviously cheaper,
they put that in there
thinking they can get away with it,
and then what happens,
is that after they start driving down the road,
they start hearing knocking noise,
which is from the detonation
that's happening inside their engine.
See, that octane rating at the gas pump,
that octane rating is how much that fuel
can resist detonation,
or in other words,
the extreme pressures inside your combustion chamber.
So if you put a lower octane fuel,
it can resist it less,
and if you have an engine that's rated for 91 octane fuel
due to high compression ratios, let's say,
then you're gonna have detonation
and hear that knocking noise.
All right, next,
a lean air/fuel mixture can also cause engine knock.
And as you may know,
a lean air/fuel mixture
is whenever you have too much unmetered air
entering your engine,
or you have too little fuel
entering your combustion chamber.
Now, there are many reasons why you could be running lean.
But a couple examples are,
let's say you have a vacuum leak,
right here, let's say,
this clamp is loose,
and you have air leaking into your engine.
And since that's unmetered air,
since it's after our MAF sensor,
which is what measures the amount of air
entering your engine,
you have too much air,
so the fuel that's being pumping into your engine,
therefore, you have a lean air/fuel mixture.
And then on the fuel side,
let's say you have a clogged fuel injector,
or maybe a leak fuel pump,
that's not pumping enough,
or allowing for enough fuel to inside your engine,
and therefore, you have too little fuel to too much air,
therefore, a lean air/fuel mixture again.
And whenever you have a lean air/fuel mixture,
you combustion temperatures go up,
because fuel, actually,
has a cooling effect on your combustion temperatures,
and whenever there's not enough of that,
or too much air, to too little fuel,
your combustion temperatures go up,
therefore, why you could have a detonation
and have engine knock.
Next, if you put wrong spark plugs in your engine,
you could also experience engine knock.
See, different spark plugs come with different heat ranges.
Now, if you put a wrong spark plugs,
or a spark plug that's not recommended for your engine
inside your engine,
and cannot withstand that heat,
it's gonna stay too hot for that engine,
therefore increase the temperatures
inside the combustion chamber,
which could lead to detonation.
Also, the same thing can occur
with badly worn spark plugs as well.
Next, over advanced ignition timing,
could also cause detonation.
And when we're talking about ignition timing,
we're talking about when your car's computer
or ignition control module
tells your ignition coil to fire spark
at your spark plug.
And it usually happens
depending on different variables
about five to, let's say,
30 degrees before the piston reaches top dead center.
Now, let's say you're working on a car
that you can actually advance or retard the ignition timing,
maybe with the distributor,
and you accidentally over advance it,
and where it's supposed happen,
let's say, 15 degrees before top dead center,
it happens five degrees before top dead center.
And when that happens,
you end up having too much pressure
inside your combustion chamber,
which could lead to detonation.
Next up, a bad knock sensor could also cause detonation.
All right, so the job your knock sensor,
as the name would suggest,
is to basically sense knock coming from your engine,
perhaps due to detonation.
And your knock sensor is usually bolted
to the side of your block,
as you can see here.
And when your car's computer senses knocking
coming from your engine through your knock sensor,
what it does is it Donald Trumps the ignition timing,
therefore reducing the pressure
that's inside your combustion chambers,
which help to get rid of engine knock.
Now, the problem is,
if an engine's on the different loads,
I experience minor or mild detonation or engine knock,
and the knock sensor helps your car's computer
to adjust for that.
But when you don't have a working knock sensor,
or knock sensor that's transcending the wrong signals
to your engine,
it throws the whole timing off,
and therefore,
it could actually lead to experiencing engine knock.
All right, next,
the excessive carbon buildup could also lead to detonation.
All right, so as you can see in this combustion chamber,
we have some carbon buildup,
but it's not extreme or excessive.
But let's on engine,
we just have an extreme amount of carbon buildup,
let's say, on these valves,
all over the combustion chamber,
and that could lead to detonation,
because it basically increases our compression ratio,
which basically means our air/fuel mixture
has to be squeezed into a small area
at our combustion chamber.
And when that happens,
you buildup a lot of pressure and heat,
and that could lead to detonation.
All right, now this list is getting pretty long,
but there's one last thing you need to check,
and that's if you have a bad EGR.
Now, as some of you may know,
your EGR system is responsible for recirculating
some of your exhaust gases
through your exhaust manifold or your exhaust pipes.
That gets in your engine and into your combustion chambers
in order to reduce the combustion temperatures there.
So your exhaust gases have very little oxygen content,
because it has already been burned up
inside your engine.
So basically, your EGR system reintroduces that inner gas
back into your combustion chambers,
which takes up a little bit of space there,
but it helps to reduce the combustion temperatures there.
And whenever your EGR system fails,
maybe due to an EGR valve that's not opening,
or an EGR solenoid that's not working properly,
your combustion temperatures go up,
therefore, you're gonna have detonation.
All right, enough of that.
So now let's go on to diagnosing your detonation issue
on this car.
And I know it's an engine knock or detonation issue,
because the owner tells me that the engine knocks
whenever he puts in regular gas,
but as soon as he puts in
a premium or higher octane gas in it,
the knock goes away.
But the problem is that this engine
is supposed to work properly just on regular gas,
and not need higher octane fuel
in order for it to not have detonation,
unless there's something wrong.
So that's what we're gonna diagnose today.
So first thing we're gonna do,
is to grab our good old scanner,
and connect it to our car's computer,
and run a scan and see whether we have any fault codes,
especially any codes related to our EGR system,
or knock sensor, maybe,
or any related or could affect our timing as well.
Also, as always,
if you're interested in this scanner,
or any other tools or products I might using in my videos,
I put links to where you can buy them for cheap online
down below in the description box.
So don't be afraid to click on it,
and check them out.
All right, so with Key On Engine Off,
I'm just gonna do an auto scan.
This way it scans all the control modules on this car,
so that way we won't miss anything.
So there, it scanned five control modules.
And the most important one for what we're doing,
was our PCM, or Power Control Module.
And as you can see,
none of these modules have any fault codes.
All right, so now we don't have any fault codes,
what we're going to do next is start our engine
and look at some live data.
We're gonna look at our short and long term fuel trims,
see whether we're running lean or not,
also look at our O2 sensors,
and make sure they're working properly,
and go from there.
All right, so we'll choose our Power Control Module.
We'll go to live data.
All right, so we've got a long list of data pids
on this scanner,
which is great.
So now I'm just gonna choose the ones
that are related to what we're doing.
So here's a list I got.
We've got our oxygen, our MAF sensor,
Mass Air Flow sensor at 1.1 volts at idle,
which is about normal.
And then we got our oxygen sensors.
This is our bank one, sensor one,
bank two, sensor one.
These are pre-cat oxygen sensors.
They sense the oxygen that's coming out of our engine.
And they should be oscillating from .1 to about .9 volts.
And as you can see, they both are.
Here you can see it better on this graphing feature.
As you can see,
it's going from about .1 to about .7, .8.
And that's the case with both of them.
And that's what you want to see
on your pre-cat oxygen sensors.
And then here,
we have our post-cat oxygen sensors
for bank two, sensor two,
and bank one, sensor two.
These are there to mainly monitor the efficiency
of your catalytic converters.
Sometimes they're used for adjusting your air/fuel mixture.
I don't think it's the case for this car,
but that's just something you want to keep in mind.
Next up we've got our fuel system status.
And you want to,
these all don't mean anything unless this is in closed loop.
And as you can see,
we're in closed loop.
And here on the bottom,
we've got our short term and long term fuel trims
for both of our banks.
So the first one,
we got bank one,
short term, bank one.
Long term here.
And here's a graph for our short and long term
for bank one,
on the bank on the short term.
Because you can see we're pretty much averaging
pretty close to zero,
which is about perfect.
And on the long term,
you can see it's a negative 3.5,
negative four,
which means that it's taking a little bit of fuel away,
but it's not excessive.
The rule of thumb is that,
when you add these you don't want to see
anything greater than negative or positive 10,
when you add them up for each bank.
And here's the number for our short and long term fuel trims
for bank number two,
as you can see.
Again, these numbers are really good as well.
They're pretty much nearly perfect.
All right, so going down this list,
we know that we don't have a fuel issue.
That's not our problem.
We don't have a lean air/fuel mixture.
Timing is not an issue.
No indication of a bad knock sensor.
We don't have a bad EGR valve,
because on this car, funny enough,
we do not have an EGR system.
So what we're basically left with
is either excessive carbon buildup,
or wrong spark plugs.
Now, unfortunately,
I do not have a borescope
to show you the inside of this engine
to see whether we have excessive carbon buildup or not,
but we're actually replace the spark plugs on this car,
because I'm pretty sure they're not the wrong spark plugs,
but according to the owner,
the sparks plug on this car,
which has about 160,000 plus miles,
have never been replaced as far as he knows.
So there's a high probability
that those badly worn spark plugs in there
are getting to hot,
and increasing the combustion temperatures in our engine,
and therefore causing our detonation issue.
All right, so I won't bore you
with the replacement procedure,
I'll just give a shot of what the old spark plugs look like,
and then compare them to the new ones.
There's what the first spark plug that I pulled out
out of this engine looks like.
And I think you guys can see the problem.
You guys see our spark plug gap?
It's not supposed to be about a quarter of an inch.
It is Motorcraft,
so it's the right spark plug for this car.
But as you can see,
it's simply badly worn out,
whereas the gap between our electrode and our grounding tip
is double this new one,
which is properly gap,
and that's probably what's causing our detonation issue.
All right, so now it's about an hour later,
and we replaced our spark plugs,
and all of our spark plug wires as well.
So now all that's left to do
is to go in our test drive,
see whether we've solved our issue or not.
Now, unfortunately,
I don't have any before shots,
where this engine was making that knocking noise.
But it was doing, basically, under load,
and then that's when you get most of knocking,
when you're having engine knock issues.
And as you can see,
we're going uphill now,
and RPM around 3000,
and no knocking whatsoever.
Still going uphill,
kind of flooring it.
No issues.
So that's it folks.
Hope you enjoyed watching this video.
If you did,
do me a favor and check out these other related videos,
of which I put links to on this side of the screen.
There will also be links down below
in the description box as well.
All right, thanks for watching.
I'll see you guys next time.
(rock music)