Engine knocks at low RPM

My engine all of a sudden seems to have developed knocking on low RPM
yesterday. This is a 1999 Nissan Maxima at 110,000 miles and I did all
the required maintenance. While I was bring it to a local mechanic,
the "service engine soon" light came on. The mechanics read the code
and it is something like "knock sensor malfunction", and "#2 misfire",
or something like that.

The mechanics is all booked this week so I will bring my car in on
Monday for further diagnostics. In the mean time, someone suggested
replacing my spark plugs to see if it helps, I know it was replaced at
60k, and maybe at 90k, not sure. So I replaced it this morning myself,
double platinum plugs and gapped at 1.1mm, according to the repair
manual. The 3 plugs in the front of the engine (easier to access to)
seems aged less than the 3 plugs in the back. So perhaps the 3 in the
back was not replaced previously?

Unfortunately the problem remains. At low RPM, such as when I am
driving on street, I can feel the steering wheel shake slightly. If I
put it on neutral, it doesn't shake as much, but I can still feel the
engine not running evenly/smoothly. At high RPM however, such as
highway driving, the problem almost disappears.

I am not a car person and replacing the spark plug is about as brave
as I am willing to go. I was hoping that it is the cause but it's not.
What other factors could be causing the engine knock? Anything I can
do to check myself? My car does not have a distributor cap, and the
cable for the spark plug does not look like it can be replaced either.

I've did all the required maintenance, 60k, 90k, etc. but not an
engine tune-up. Could this be because I didn't do any engine tune-up?

Thanks!

Raymond

On Fri, 9 Mar 2007 22:59:11 +0000 (UTC), wrote:

>
>My engine all of a sudden seems to have developed knocking on low RPM
>yesterday. This is a 1999 Nissan Maxima at 110,000 miles and I did all
>the required maintenance. While I was bring it to a local mechanic,
>the "service engine soon" light came on. The mechanics read the code
>and it is something like "knock sensor malfunction",

Just about every late model V6 Nissan on the road will have that code.
It refers to a device which is essentially a tuned microphone to
detect "ping" and command the computer to retard the timing to
suppress it. It won't make a rat's ass unless your car is vulnerable
to "pinging" due to low octane fuel, carbon deposits or other factors.

> and "#2 misfire",

This is what needs to be diagnosed and repaired. Possible bad coil.
And #2 misfire is what turned the light on -- the knock sensor fault
does not.

>or something like that.
>
>The mechanics is all booked this week so I will bring my car in on
>Monday for further diagnostics. In the mean time, someone suggested
>replacing my spark plugs to see if it helps, I know it was replaced at
>60k, and maybe at 90k, not sure. So I replaced it this morning myself,
>double platinum plugs and gapped at 1.1mm, according to the repair
>manual. The 3 plugs in the front of the engine (easier to access to)
>seems aged less than the 3 plugs in the back. So perhaps the 3 in the
>back was not replaced previously?
>
>Unfortunately the problem remains. At low RPM, such as when I am
>driving on street, I can feel the steering wheel shake slightly. If I
>put it on neutral, it doesn't shake as much, but I can still feel the
>engine not running evenly/smoothly.

Almost certainly it still has the #2 cylinder misfire.

Don in Austin
www.donsautomotive.com

> At high RPM however, such as
>highway driving, the problem almost disappears.
>
>I am not a car person and replacing the spark plug is about as brave
>as I am willing to go. I was hoping that it is the cause but it's not.
>What other factors could be causing the engine knock? Anything I can
>do to check myself? My car does not have a distributor cap, and the
>cable for the spark plug does not look like it can be replaced either.
>
>I've did all the required maintenance, 60k, 90k, etc. but not an
>engine tune-up. Could this be because I didn't do any engine tune-up?
>
>Thanks!
>
>Raymond

Low rpm and heavy throttle is the condition at which knock
(detonation) does occur. On the other hand, spark knock is primarily
an audio thing- you hear it but do not feel it.

If you feel a shaking (rather than hearing a pinging problem) that is
more like a misfire. It is possible the misfire and the knocking are
independent problems. The misfire indication is an indication that
you are getting misfire as well as knock. Now, I suppose the timing
could be so screwed up that it causes misfire as well as detonation.


On Mar 9, 4:59 pm, wrote:
> My engine all of a sudden seems to have developed knocking on low RPM
> yesterday. This is a 1999 Nissan Maxima at 110,000 miles and I did all
> the required maintenance. While I was bring it to a local mechanic,
> the "service engine soon" light came on. The mechanics read the code
> and it is something like "knock sensor malfunction", and "#2 misfire",
> or something like that.
>
> The mechanics is all booked this week so I will bring my car in on
> Monday for further diagnostics. In the mean time, someone suggested
> replacing my spark plugs to see if it helps, I know it was replaced at
> 60k, and maybe at 90k, not sure. So I replaced it this morning myself,
> double platinum plugs and gapped at 1.1mm, according to the repair
> manual. The 3 plugs in the front of the engine (easier to access to)
> seems aged less than the 3 plugs in the back. So perhaps the 3 in the
> back was not replaced previously?
>
> Unfortunately the problem remains. At low RPM, such as when I am
> driving on street, I can feel the steering wheel shake slightly. If I
> put it on neutral, it doesn't shake as much, but I can still feel the
> engine not running evenly/smoothly. At high RPM however, such as
> highway driving, the problem almost disappears.
>
> I am not a car person and replacing the spark plug is about as brave
> as I am willing to go. I was hoping that it is the cause but it's not.
> What other factors could be causing the engine knock? Anything I can
> do to check myself? My car does not have a distributor cap, and the
> cable for the spark plug does not look like it can be replaced either.
>
> I've did all the required maintenance, 60k, 90k, etc. but not an
> engine tune-up. Could this be because I didn't do any engine tune-up?
>
> Thanks!
>
> Raymond

On Mar 9, 4:59 pm, wrote:
> So I replaced it (spark plugs) this morning myself,
> double platinum plugs...

I don't know of any "double platinum" plugs other than Bosch and
(maybe) Autolite. They are junk. IIRC, your engine came with NGK
single ground platinum plugs. If you did use Bosch plugs, toss them
in the nearest garbage receptacle and get thee the proper NGKs for
about $12 - $14 each, so that you don't further complicate your
drivability issues.

> Unfortunately the problem remains. At low RPM, such as when I am
> driving on street, I can feel the steering wheel shake slightly. If I
> put it on neutral, it doesn't shake as much, but I can still feel the
> engine not running evenly/smoothly. At high RPM however, such as
> highway driving, the problem almost disappears.

You could have a vacuum leak at one port of the intake manifold (I'm
guessing near cylinder #2). You could have an intake or exaust valve
not sealing in cylinder #2. The phrase 'almost disappears' is too
vague to comment accurately on, so I can only speculate. If there is
*always* some level of misfire present, then one could suspect either
an ignition coil or fuel injector, both common problems on Nissans for
many years. A weak coil would be my first instinct, knowing this is a
Maxima 3.0. They had several designs through the years (even on
different Maxima bodystyles) that suffered high failure rates.

> I am not a car person and replacing the spark plug is about as brave
> as I am willing to go.

Use that braveness to reinstall NGK plugs in your engine.

> I've did all the required maintenance, 60k, 90k, etc. but not an
> engine tune-up. Could this be because I didn't do any engine tune-up?

Not likely. The OE plugs can go a long time without causing
drivability symptoms or stressing the ignition coils. Plugs simply
are recommended to be replaced at intervals which are designed to keep
their degradation to a minimum, as calculated by the plug and auto
engineers.

The best bet is to have a competent mechanic experience the noise/
shake/whatever you are complaining about -- show him so you are both
on the same page, then he can go right to the most appropriate testing
to diagnose your car properly and with the lowest labor cost. I don't
have a comfortable grasp of your symptoms as written in text, so don't
assume a service writer will be able to convey exactly what you mean
to the mechanic. Ask to go on a quick test drive to show him if
necessary.

Toyota MDT in MO

In rec.autos.tech Comboverfish > wrote:

> On Mar 9, 4:59 pm, wrote:
> > So I replaced it (spark plugs) this morning myself,
> > double platinum plugs...

> I don't know of any "double platinum" plugs other than Bosch and
> (maybe) Autolite. They are junk. IIRC, your engine came with NGK
> single ground platinum plugs. If you did use Bosch plugs, toss them
> in the nearest garbage receptacle and get thee the proper NGKs for
> about $12 - $14 each, so that you don't further complicate your
> drivability issues.

> > I am not a car person and replacing the spark plug is about as brave
> > as I am willing to go.

> Use that braveness to reinstall NGK plugs in your engine.

Are you serious? I don't remember the specific brand I got, I'll
find out tonight. But I do remember the one I taken out was NGK. If I
replaced it with something else, is it really that big of a deal?

Pep Boys also sells some Iridium type of plugs, and the price is about
$14 each. Are those better?

Which type do I need:

http://www.ngksparkplugs.com/product...x.asp?mode=nml

Thanks!

Raymond

On Sun, 11 Mar 2007 21:58:24 -0400, lugnut >
wrote:

>On Fri, 9 Mar 2007 22:59:11 +0000 (UTC),
>wrote:
>
>>
>>My engine all of a sudden seems to have developed knocking on low RPM
>>yesterday. This is a 1999 Nissan Maxima at 110,000 miles and I did all
>>the required maintenance. While I was bring it to a local mechanic,
>>the "service engine soon" light came on. The mechanics read the code
>>and it is something like "knock sensor malfunction", and "#2 misfire",
>>or something like that.
>>
>>The mechanics is all booked this week so I will bring my car in on
>>Monday for further diagnostics. In the mean time, someone suggested
>>replacing my spark plugs to see if it helps, I know it was replaced at
>>60k, and maybe at 90k, not sure. So I replaced it this morning myself,
>>double platinum plugs and gapped at 1.1mm, according to the repair
>>manual. The 3 plugs in the front of the engine (easier to access to)
>>seems aged less than the 3 plugs in the back. So perhaps the 3 in the
>>back was not replaced previously?
>>
>>Unfortunately the problem remains. At low RPM, such as when I am
>>driving on street, I can feel the steering wheel shake slightly. If I
>>put it on neutral, it doesn't shake as much, but I can still feel the
>>engine not running evenly/smoothly. At high RPM however, such as
>>highway driving, the problem almost disappears.
>>
>>I am not a car person and replacing the spark plug is about as brave
>>as I am willing to go. I was hoping that it is the cause but it's not.
>>What other factors could be causing the engine knock? Anything I can
>>do to check myself? My car does not have a distributor cap, and the
>>cable for the spark plug does not look like it can be replaced either.
>>
>>I've did all the required maintenance, 60k, 90k, etc. but not an
>>engine tune-up. Could this be because I didn't do any engine tune-up?
>>
>>Thanks!
>>
>>Raymond
>
>
>Your maxima is about the right mileage to start experiencing
>coil failure(s). It has a coil for each plug. We have a
>couple of that vintage in the family that have had this
>problem and the dealer tells us it is common. Their
>recommendation is to replace them all as a set to avoid the
>reasonable certain failure of more of them costing a
>diagnostic charge each time.
>
>Also, make sure you use nothing other than the OEM type NGK
>plugs. They don't seem to like any others. As another
>oster said, if you have the Bosch plugs, you just wasted
>your time and money. The old NGK's were probably still
>better plugs.
>
>Your problem have little or nothing to do with routine
>maintenance. Keep following your maintenance schedule. I
>understand the replacement Nissan coils are updated and
>better quality. You can get them for much less money in the
>aftermarket. Expect to spend a few hundred bucks for coils
>but still chaeper and less of a hassel than one at a time.
>Once you get this problem ironed out, the knock sensor
>problem won't be one. The engine is knocking because it has
>one or more cylinder not producing the power they should.
>This is just more work for the others which may result in
>knock.
>
>Lugnut

Lugnut is right target here regards the coils, the spark plugs. Cheap
Bosch plugs DO cause misfire. When I first heard that I thought it
was a case of someone with an axe to grind but I have seen it
firsthand.

Regards the knock sensor however --- it is a known and common problem
for the sensor to fail. Engine "knock" does not turn on the light --
a filed sensor does. The code will remain ater the misfire -- which I
think you are describing as "knock" -- is cured. The knock sensor
code will not turn on the check engine light. If the motor is subject
to low octane fuel or other factors that cause knock or "ping" the
motor will not have the benefit of knock suppression from the knock
sensor commanding the computer to retard timing. This may or may not
ever be any problem at all. Local emissions inspection may or may
not be a problem.

Don
www.donsautomotive.com

lugnut > wrote:

> As far as Bosch plugs, it is a shame that an, otherwise,
> reputable name like Bosch is on such a crappy plug. I have
> no idea what their problem is but, I installed them in all
> of my vehicles a few years back - no idea why I had such a
> brain fart! I replaced every one within a few weeks because
> of misfires. Went back to OEM plugs in everything which is
> what my philosophy has been most of the 50+ years I have
> screwed around with engines - problem solved. Unless there
> is a damn good reason based on engine modification or
> manufacturers recommendation, there simply is no good reason
> to use anything else for routine maintenance, and several
> reasons to stay with the OEM. They almost always work
> properly.

Ok, what I have is "CHAMPION DOUBLE PLAT Spark Plug".

Went to the mechanics today, he said it's also likely the coil. He
said the way they test it is to swap the #2 with the #3, clear the
code, and see if the mis-fire follows the coil.

Is it expensive to replace the coil? Should I just replace all 6?

Thanks.

Raymond

lugnut > wrote:

> The coils are around $80ea/US around here. I am told there
> are aftermarket brands available for about half that. The
> mechanic is correct that you can test by swapping the coils.
> You can replace just one coil and take your chances that
> there will be no further coil problems. It has been my
> experience and that of the dealers around here that
> subsequent failures are soon likely if all are not replaced.
> If you are handy, you could replace them yourself.

> You may want to look here. This is not a recommendation. It
> just shows them and online availability if you want to
> tackle it yourself

Is the coil the same as the "coil pack" mentioned here?

How to Change Your Spark Plug (from
http://forums.maxima.org/showthread.php?t=512892)

http://www.vqpower.com/v2/modules.ph...howpage&pid=33

If that's the case, it is indeed very simple to replace. The
technician just called me and told me the #2 coil did not lit, and
quoted me a price of $109 to replace it.

Raymond

lugnut > wrote:

> The coils are around $80ea/US around here. I am told there
> are aftermarket brands available for about half that. The
> mechanic is correct that you can test by swapping the coils.
> You can replace just one coil and take your chances that
> there will be no further coil problems. It has been my
> experience and that of the dealers around here that
> subsequent failures are soon likely if all are not replaced.
> If you are handy, you could replace them yourself.

The mechanics replaced the #2 coil, and the problem is fixed. He
replaced it with an STI #5001 coil. He said it is an aftermarket
brand, but it is labeled for Infinity/Nissan.

Is STI a good equipment manufacturer? Are the $80 you mentioned OEM
coils from Nissan? Where would I get those?

Thanks.

Raymond

lugnut wrote:

>
> As far as Bosch plugs, it is a shame that an, otherwise,
> reputable name like Bosch is on such a crappy plug.

And such crappy oxygen sensors, and a few other things. Bosch (like many
auto parts companies) seems to have a split personality. Their OEM parts
line and some other parts are built in their own factories and to high
standards of design and production. Aftermarket parts are a mixed bag
with many being re-badged third-party parts (eg, the O2 sensors).


But the plugs are the real mystery- regardless of where the plugs are
produced the flaw is inherent in the original Bosch Platinum plug design
that's been around for 20-odd years. Its as if the engineers that
designed and review the design of that plug just refuse to believe the
real-world evidence that overwhelmingly says the hair-thin center
electrode is a bad idea.