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

Reply to
nospam.car
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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.

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.

Almost certainly it still has the #2 cylinder misfire.

Don in Austin

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Reply to
Don

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.

Reply to
Don Stauffer in Minnesota

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.

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.

Use that braveness to reinstall NGK plugs in your engine.

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
Comboverfish

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:

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Thanks!

Raymond

Reply to
nospam.auto

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

Reply to
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

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Reply to
Don

I think another part of the problem is the way a misfire is handled by the system where the unburned fuel resulting from a misfire is sensed as a rich mixture. The PCM then leans the mix making it more susceptible to detonation or ping. Problems like this do tend to snowball with other side effects that are only symptoms of the real problem.

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.

Lugnut

Reply to
lugnut

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

Reply to
nospam.auto

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

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Lugnut

Reply to
lugnut

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

How to Change Your Spark Plug (from

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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

Reply to
nospam

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

Reply to
nospam

Glad you got it taken care of. Coil pack/coil same thing in most cases. I am not familiar with that brand. Should be OK if it is warranted. The $80 price I noted was over a year old since that is the last I paid. Prices vary considerable around he country. Lately, here in the Atlanta area, we are trying desparately to catch up with NY or CA with high prices.

Good luck

Reply to
lugnut

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.

Reply to
Steve

Since when have engineers been responsible for the popularity of a product? :-)

As much marketing force that's created by Bosch's aftermarket division and help received from conglomco giants like Autobone, there's no wonder their crap flies out the door. No amount of real world testimony is ever going to stop people from trying to "save a buck" or dissuade them from recognizing the name Bosch, and therefore associating it with the concept of quality.

Toyota MDT in MO

Reply to
Comboverfish

O2 sensors react to oxygen content, not a "rich mixture". A misfire of this variety is likely to be oxygen-rich (no pun intended). The air in the cylinder has not had a chance to completely (properly is a better word) catalyze the fuel burn due to the lack of a proper ignition event. High hydrocarbon level and higher O2 output is to be expected in a weak spark related misfire.

Regarding your recommendation that aftermarket coils are a viable idea, I will not use them personally. I have heard and read too many stories of tail-chasing regarding several different generations of the Nissan 3.0 coilpack. I.E. tech chases a P1320 code (coils usually don't test bad with scope and often no misfires present) and puts on one - six A/M coils. P1320 returns and the process continues. It seems they aren't the same or even roughly equivalent... It's too late to tell the OP; I haven't been on in a few days...

Toyota MDT in MO

Reply to
Comboverfish

The coil pack the Mechanics replaced seems to work fine (It was STI brand, not the OEM one). I noticed a definite increase in power when I accelerat, and the engine runs quiter too. Not sure if those are due to the replaced spark plug, or the coil pack.

I finally managed to find a 1/2 to 3/8 drive adapter, and managed to check the torque setting on my spark plugs. (I have a 1/2" torque wrench, and the spark plug tools were all 5/8). I was worried that I might have over tightened it, but it seems OK. I torqued it at 19lb now.

I have ordered some NGK PFR5G-11 plugs from an ebay dealer, and I'll replace the Champion plugs I put in with these once it arrives. Probbaly will take me just an hour instead of the 4 it did initially. :)

Thanks everyone!

Raymond

Reply to
nospam.auto

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
dlowrie

"Comboverfish" wrote in news: snipped-for-privacy@h3g2000cwc.googlegroups.com:

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.

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Reply to
Tegger

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