Engine knocks at low RPM

Thread view:

Enable EMail Alerts

Start New Thread

Thread rating:

nospam.car@none.com - 09 Mar 2007 22:59 GMT

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

Reply to this Message

Don - 10 Mar 2007 05:01 GMT

>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 a.s 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.
>
[quoted text clipped - 11 lines]
>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.
[quoted text clipped - 11 lines]
>
>Raymond

Reply to this Message

Don Stauffer in Minnesota - 10 Mar 2007 15:01 GMT

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, nospam....@none.com 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
[quoted text clipped - 30 lines]
>
> Raymond

Reply to this Message

Comboverfish - 10 Mar 2007 17:30 GMT

On Mar 9, 4:59 pm, nospam....@none.com 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

Reply to this Message

nospam.auto@none.com - 12 Mar 2007 01:37 GMT

In rec.autos.tech Comboverfish <comboverfish@yahoo.com> wrote:

> On Mar 9, 4:59 pm, nospam....@none.com 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/products/spark_plugs/index.asp?mode=nml

Thanks!

Raymond

Reply to this Message

dlowrie@nc.rr.com - 29 Mar 2007 03:35 GMT

NGK Platinums are reccomended, changed every 75k...

Ignition coils (mounted on each spark plug) are notorious going bad on
these cars, some even as early as 50k that most certainly is your
problem, the knock sensor code shows up along with most other codes
thrown in this car, swap the #2 coil with another one and see if the
misfire moves with it...than thats your culprit.

Reply to this Message

Tegger - 29 Mar 2007 12:45 GMT

> On Mar 9, 4:59 pm, nospam....@none.com 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.

NGK uses the term "double platinum" to refer to _both_ positive and
negative electrodes being coated with platinum. They also put a dot of
platinum on the underside of the ground electrode.

http://www.ngkntk.com.br/site_ingles/velas/dupla_platina.html

Signature

Tegger

Reply to this Message

Rate this thread: