Bad EGR Valve?
 

Hello,
My car
2000 Honda Prelude, 84k miles

Recently, it pumped out black smoke under full throttle, but the black
smoke disappeared after I replaced all the spark plugs. I'm facing a
different problem now. At around 1500 RPM, the engine sorta knocks. It
sounded like twirling a plastic bottle with a few marbles in it. Is this
the sound of engine knock? Anyway, If I keep the engine at around 1500 RPM
at neutral, then surely, there would be this noise. And if I race the
engine and then let it fall back down to idle, right before it's to hit 1500
RPM, there is this noise. I do not hear this noise at idle or at higher
RPMs. Does this sound like a bad EGR Valve? Or bad valve lifters or rocker
arms? How would one go about troubleshooting this problem?

TIA
Andy

Is the check engine light on? Does the noise coming from the top end
or the bottom end of the engine? GET a screwdriver or mechanics
stethescope to isolate where the problem may be. It could be a noisy
valve train. It sounds like you don't have a engine bearing problem, or
anything that has to do with the bottom end. Because a bearing knock
will rise in noise level as the engine has a load on it and gets loader
as a more of a load is put on. There a diagnosis you can do if it was
maybe be a cracked flexplate. Raise the engine speed to high idle
(1500-2000 RPM), then turn the ignition switch off. Before the engine
stops, turn the ignition back on. If a knocking sound is heard when
the engine restarts, the flex plate is cracked. To test a EGR valve you
will need a vacuum pump with gaugue. To do this would be a lot to type.
Also its possible that the black smoke is coming from a defective
EGR valve but you replace the spark plugs to temporarily get rid of the
smoke. What was the condition of the plugs? Did they have some carbon
built up on them? You can aslo do a vacuum gauge test to verify a
engine problem associated with this issue by unhooking the brake
booster hose and put a gauge on it while at idle. Different readings
mean differnent things. With so many sensors it is really hard to
determine what the root problem is.

Not familiar with model but on my car gently push up on the EGR diaphragm
(underside of valve) and feel if it moves smoothly. Also can feel
diaphragm with finger tip to see if moving when throttle opened. If not it
could be dirty and sticking. If you gently push up on diaphragm when
engine idling, engine will stumble. Not difficult to remove and clean EGR
valve. I wrote a description of cleaning mine for my website (see below)
under "Cars".


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"Garry" > wrote in message
oups.com...
> Is the check engine light on?

No, the engine light is *not* on. As a matter of fact, I removed the
EGR Valve positon sensor output from the valve and reved the engin in
neutral and the engine light still would not turn on. I'm thinking the ECU
might not even operate the valve in neutral.

> Does the noise coming from the top end
> or the bottom end of the engine? GET a screwdriver or mechanics
> stethescope to isolate where the problem may be. It could be a noisy
> valve train. It sounds like you don't have a engine bearing problem, or
> anything that has to do with the bottom end. Because a bearing knock
> will rise in noise level as the engine has a load on it and gets loader
> as a more of a load is put on.

The noise seems to be more clear on the driver side on top of the timing
belt-water pump area with a stethescope. Come to think of it, the noise
seemed to have started after I took the car in for a radiator flush at
around 50K. The dealer did a back-flush, but I seem to remember from some
Honda tech manual that you're not suppose to back-flush the radiator. Could
the knocking come from the water pump? But only at around 1500RPM?

> smoke. What was the condition of the plugs? Did they have some carbon
> built up on them?

The plugs looked perfectly normal with no sign of detonation,
pre-ignition, nor carbon build-up. I guess that means I do not have a
engine knocking problems then right?


Andy

I only vaguely recall the valvetrain setup, but you do have a VTEC
engine... there could be a valvetrain problem with the VTEC lifter
components which only makes noise as the ECM is adjusting valve lift
with the oil pressure control solenoid. Perhaps the rocker shafts are
worn where the VTEC rockers operate. If this were deemed by an
experienced ear to be likely, a simple removal of the valve cover would
reveal the shafts and rockers for some rudimentary inspection. For
that matter, the regular rockers could be worn also. It is hard to
diagnose from a static, written description.

Toyota MDT in MO

I don't know, I took it to a Honda Dealer and they seemed to think it is
the water pump, but all this diagnosis seemed a little fishy because I did
asked about a timing belt and water pump change a few days prior to today's
"diagnostic". They recommend changing the timing belt and water pump and a
$350 valve maintainance and they said this might not even be the problem and
that I might have a timing belt tensioner problem and worst yet, they said
Honda Care would not cover all this because this is normal maintanance. I
called Honda Care and they told me that if the engine is making noise, then
they will cover it. It all seemed too fishy so I'm taking my problem to the
dealer whom I broght the car from.
But anyway, doesn't the VTEC kicks in at around 5600 RPM? Would a bad
valve train 'cause persistance noise at a small range of constant engine
RPM?

Andy


"Comboverfish" > wrote in message
ps.com...
>I only vaguely recall the valvetrain setup, but you do have a VTEC
> engine... there could be a valvetrain problem with the VTEC lifter
> components which only makes noise as the ECM is adjusting valve lift
> with the oil pressure control solenoid. Perhaps the rocker shafts are
> worn where the VTEC rockers operate. If this were deemed by an
> experienced ear to be likely, a simple removal of the valve cover would
> reveal the shafts and rockers for some rudimentary inspection. For
> that matter, the regular rockers could be worn also. It is hard to
> diagnose from a static, written description.
>
> Toyota MDT in MO
>

Andy Chang wrote:

> I called Honda Care and they told me that if the engine is making noise, then
> they will cover it. It all seemed too fishy so I'm taking my problem to the
> dealer whom I broght the car from.

That sounds like a good plan. Your extended warrantee should cover
abnormal engine noise regardless of cause, unless a normal maintenance
item (timing belt) was neglected. I think the Honda recognized
interval for that belt is 90k. Internal components should be covered
unless it can be proven that fluid maintenance has been neglected.

> But anyway, doesn't the VTEC kicks in at around 5600 RPM? Would a bad
> valve train 'cause persistance noise at a small range of constant engine
> RPM?

I am used to what I see these days, which is Toyota's VVT-i system. It
works in a significantly different manner (with the exception of their
VVT-iL engine that uses high lift rockers like your Honda), but Toyotas
will make a subtle rattling sound at a given held RPM. If there is a
problem with the cam controller then they can get loud enough to signal
a real problem. I would agree in theory that your Prelude VTEC system
really only kicks in at high RPMs since is a valve lift adjustment, but
my knowledge of Honda's system is very slight.

Toyota MDT in MO

On Sat, 8 Jul 2005, Comboverfish wrote:

> That sounds like a good plan. Your extended warrantee should cover

Warrantee: The party to whom the warrantor makes a promise. In this case,
a vehicle owner.

Warranty: The promise made by the warrantor to the warrantee.

Daniel J. Stern wrote:
> On Sat, 8 Jul 2005, Comboverfish wrote:
>
> > That sounds like a good plan. Your extended warrantee should cover
>
> Warrantee: The party to whom the warrantor makes a promise. In this case,
> a vehicle owner.
>
> Warranty: The promise made by the warrantor to the warrantee.

Right. I had "guarantee / guaranty" on the brain, which have for all
purposes the same definition (not that many people use the latter
spelling).

I forgot that "warrantee / warranty" are not synonymous. As a fellow
grammer cop, I thank you!

Toyota MDT in MO