MISFIRE..DRIVING ME NUTS...PLEASE HELP 97 Q45

[tt300z]

Ok.. where should I start ..i have a 1997 infiniti q45 and have been experiencing a problem for some time now and can’t figure it out or better said I would like a second opinion.. I had the car for one year now and after a few mouth it started to back fire little once at stop lights…well at that time I got a new fuel filter and put gas additives and after that it did it a bit here and there and even went away until recently when it came back …but this time is bad…..Now what happens turn can in the morning let it warm up….start to drive and car feels like it has now power for the first 15min of driving …well it comes and goes like it comes in and then goes and shakes the car when it comes and goes…but before it did that it would only do it at idle….a little misfire here and there…but if you TURN ON LIGHTS TURN ON A/C ON MAX AND JUST ABOUT EVERYTHING ELECTRICAL …it will sit there and misfire one after another . but only in DRIVE what I mean if there is a lot of load it will misfire a lot if no load maybe a small one…

Now what have I done….did a fuel pressure check …GOOD…. Change the spark plugs… and just yesterday I checked the coil packs….. ohm between TB and GROUND on 5 of then I get 1.5 and some on 2 I get 1.4 and some……and on 1 I get 1.3 and some ….. ok well I look in the manual and I can’t find anything on the specks on ignition coils…BUT LIKE I SAID the problem is there and is not ….and lets say when the car is running crapy it doesn’t misfire at idle but still runs good but I do notice a difference when I rev the engine ….it revs slower then when its running good…..Anyway if anyone can help me out with some advice…please its driving me nuts and I don’t really want to go get a diagnostic since I never do and like to figure out the problem myself

Oh one more thing that I’ve noticed …ok I put the key in the ignition switch and turn it to ACC …and not start the car obviously ….i press gas pedal and I hear a buzzing noise coming from the transmission….so I went and looked in the manual and found out that connected to the throttle body positioning sensor there is on plug that goes to the transmission which acts the manual says when pedal is press half way it doesn’t open and anything over half pedal it opens…..well when I press pedal anything less then half it buzzes….so I went and unplugged the plug from throttle PS and the overdrive light started to blink but no more buzz….that was just one other thing I wanted to put in here to see if it has anything to do with my problem Sorry I wrote so much but I LOVE MY NISSANS

[maxnix]

Maybe a little editing could help me follow your post.

Just the facts, sir, in simple and concise declaritive prose will suffice.

[bullittandy]

This a somewhat common problem on 97+ Q45's. The fuel filter and plugs were good first steps. It might be a good idea to do a complete maintainence overall, all fluids, filters, pvc etc. Included in this would be to clean the MAF sensor wire and throttle body, both with special cleaners avaiable at any parts store. Also wiggle the MAF sensor wires/connector.

It also sounds like your knock sensors are gone, buy two new ones and the harness and it should regain its power. If you replaced the plugs you can handle the sensors.

Search for "stumble" "misfire" and "knock sensor" and you'll get a few leads. Tip you do not have to take off the intake to do the knock sensors, its teious but a simple R&R.

I had the same stumble, very slight but I can't say what cured it, I did all of the above.

Good luck, I know the crazy feeling!

[tt300z]

maxnix thanks for looking at my post...but this is a car crazy place not an english class...

[maxnix]

maxnix thanks for looking at my post...but this is a car crazy place not an english class...

Comprehension is aided by clarity when the only description is text on the internet. If you do not care to craft your description well enough to acheive this clarity, why should anyone expend the time trying to guess what you are trying to say?

It is a difficult life for one who cannot master his native language. It is severely limited one for anyone who does not even care.

Good luck.

[bullittandy]

why should anyone expend the time trying to guess what you are trying to say?

Good luck.

You're right, take your own advice and save YOUR time by not posting and being quiet.

Your not trying to help anyone-which is the point of these boards.

[maxnix]

Your not trying to help anyone-which is the point of these boards.

The studiously ignorant are beyond help, as you well know, Andy.

[tt300z]

It is a difficult life for one who cannot master his native language. It is severely limited one for anyone who does not even care

First of all English is not my native language and i do the best i can...Second of all i think you are ignorant for saying something you have no clue about....and it seems that you don't know anything about cars since you here picking at people for the way they write and third of all I think you are an idiot for using such big words it makes me want to take a ****.And now I know you going to reply to the post….cause you like a little ***** that has to have the last word…AND BY THE WAY I FIGURED OUT MY PROBLME but I am not going to post since you say I don’t post and I just like for people to figure out my problem…..and its people like you that make nico look bad

Get a life homie

[bullittandy]

It is a difficult life for one who cannot master his native language. It is severely limited one for anyone who does not even care

First of all English is not my native language and i do the best i can...Second of all i think you are ignorant for saying something you have no clue about....and it seems that you don't know anything about cars since you here picking at people for the way they write and third of all I think you are an idiot for using such big words it makes me want to take a ****.And now I know you going to reply to the post….cause you like a little ***** that has to have the last word…AND BY THE WAY I FIGURED OUT MY PROBLME but I am not going to post since you say I don’t post and I just like for people to figure out my problem…..and its people like you that make nico look bad

Get a life homie

I sure hope he's not holding out because that would suck for ALL the Y33 owners with this problem. you have to be nice to people otherwise they don't share.

[tt300z]

KNOCK SENSORS IT WAS!!! LITTLE SUCKERS... 97 and up Q y33 does not need the manifold removed and i was able to do it in a few hours.... now i got that bug out and car runs in performance map at all times wooowww what a big differents .. i got my baby back... NOW I STILL HAVE THAT BUG WHERE THE CAR WILL MISFIRE AT IDLE but only in drive and if the lights are on and if i turn on the A/C too it just does it more but in the daytime with no load on it i will not do it... any ideas LET ME KNOWif you have the knock sensor problem CHANGE THE KNOCK SENSORS IT WILL MAKE YOU HAPPY TO HAVE THE V8 PUNCH AGAINLET ME KNOW ABOUT THE MISFIRE i just went ahead and order a coil pack to see if that does it when i replace the one with the 1.3ohm readding OH AND BY THE WAY THE KNOCK SENSORS ARE ON EBAY RIGHT NOW FOR 68$ EACH ...ORIGINAL NOT THE BROWN BOX AND I GOT A NEW HARNESS FROM LOCAL DEALER.. DO NOT CHEAP OUT GET THE HARNESS TOO SO IT WAS 200$ TO DO KNOCK SENSORS NOT 1000$ DEALER WANTS..COME TO ME ILL DO IT FOR YOU FOR 250$ FOR MY LABOR ILL HAVE IT DONE IN A FEW HOURS

How does the knock sensor affect timing?

--------------------------------------------------------------------------------

I've done a fair amount of driving with my Palm OS OBD-II Scanner feeding me live data with my knock sensor in various states of operation.

- Working.- Partially working.- Not working at all.- Bypassed via 470k resistor.

The knock sensor is very key to performance in this car because it tells the ECU how much ignition timing advance it can run. The more advance the better. But if the knock sensor is dead, the ECU will know this and go into a sort of safe ignition advance mapping in which your performance will just plain suck and the engine won't have much pull. 5spd guys will not notice this as much due to shorter and more aggressive gearing, but it would be especially noticeable in the automatic which has very widely spaced and long gears. So if you own a 95-99 Maxima and it just seems to have lost a lot of pep, chances are good that you knock sensor may be bad. The following info may be useful to you...

I will now try to explain the amount of ignition advance you should be getting and what you will "feel" in relation to all of this.

WORKING KNOCK SENSOR

Here is what your ignition timing advance should look like if your knock sensor is working properly.

Ignition Advance vs Throttle Position

Coasting: 0 degrees

Idle: 8-15 degrees.

Cruising: (<10% throttle), 30-40 degrees

Mild Acceleration: (10-20% throttle), 30 degrees or so.

Moderate Acceleration: (20-40% throttle), low to mid 20 degree range, may drop to about 18 momentarily.

Hard Acceleration: (40-xx% throttle but not WOT or "near WOT"): same as above.

WOT or "Near WOT" Acceleration: approx 15-25 degrees, RPM dependent.Explanation

During cruising at very light throttle, the ECU wants to run as much timing advance as possible. This helps the engine as far as being responsive and also probably helps out with emissions as well. 30-40 degrees of advance. Of course, when you get on it you are increasing the pressures in the cylinder (increasing the likelihood of detonation) and may not be able to run that much advance, so the default ignition map goes down to 20-30 degrees depending on how much throttle you're giving it. When you go WOT, or very close to WOT, there appears to be another map just for this. At WOT and lower RPM's you timing advance will start out in the mid-teen range and then slowly ramp up to the low/mid-20 degree range as you approach redline. As the engine spins quicker, it needs more advance to perform the best.

To those of you that really need to see things, here is something that may help you visualize all of this. Below is some raw data from my OBD-II scanner that I converted into a pretty Excel chart of a highway ramp acceleration run.

From samples 220-232 I am cruising up an uphill ramp in 3rd gear (5spd) playing with the throttle a bit to try and capture as much of the ECU's ignition mapping as possible. You can see that the ignition advance is varying between about 30-40 degrees with as much as 15% throttle.

Right at sample 232 or so I am at the top of the ramp. You can see that my speed remained steady at around 30 mph, but my RPM's jumped up from 2000rpm to 3000rpm. This is me seeing that traffic is completely clear, so I downshifted to 2nd for a WOT run. WOT registers at about 93%, and you can see that the ignition advance went down to maybe 16-17 degrees and slowly ramped up as the revs climbed to about 25 degrees @ 5500rpm when I shifted. The 2-3 shift landed me at about 4500rpm and ignition advance went to about 18-19 degrees and then ramped up to maybe 24 degrees @ 5500rpm and 85 mph when I backed off. You can see that throttle position dropped to about 85%, as I was not quite at full throttle, yet the ignition timing still remained at a "near WOT" condition where it gives you the same timing as full WOT would.

At sample 246 I skipped from 3rd to 5th and then just toyed with the throttle for a mile or so. As you can see once again, during cruise and light throttle the ECU wants to run as much timing as possible. 40-45 degrees appears to be the maximum advance. During acceleration the advance will be anywhere from 20-40 degrees, depending on how much throttle you are giving it. Anything from about 30% throttle and up (before the WOT map) should give you somewhere around the low/mid-20 degrees of advance, but it may drop to 18 degrees momentarily. (this observation will be important later )

During all of this the engine should feel torquey and responsive just like it should.

NON-WORKING KNOCK SENSOR

If your knock sensor is blown or disconnected, the ECU will know this and throw a "silent" trouble code, meaning it will NOT light the SES/CEL light on your dash. If you put your ECU into diagnostic mode it will give you an "0304" code for the Knock Sensor, or with an OBD-II scanner you will get P0325 which is the same thing.

With the knock sesnor either dead or disabled, the ECu will still try to run at least some ignition advance for performance and emissions, but only at very light loads. During cruising at very light throttle, I still got 30-40 degrees of advance. However, there appears to be a cut-off point at around 30% throttle where the ECU will send the timing back to a "safe map".

Cruising: 30-40 degrees (like before)

Light to mild/moderate Acceleration: (10-30% throttle), low-20 degree range.

ANYTHING above that: ( >30% throttle), 5-12 degreesSo with a bad knock sensor, your car may feel okay just cruising around. But as soon as you get on it it will just feel dead. There is a very big difference between 10 degrees of advance at heavy throttle and 20-30 degrees with a working knock sensor. With 20-30 degrees of advance there is a lot more torque and the engine will be very zippy. But with only around 10 degrees of advance before the piston reaches the top of the stroke, there is hardly any time for the combustion process to get started, and therefore not nearly as much power available to thrust the piston downward with. The engine is not nearly as responsive and doesn't have nearly as much torque. Your right foot notices this lack of acceleration, and you compensate for it by opening the throttle a lot more than you would normally have to just to get the same acceleration assuming your knock sensor was working and giving you as much advance as possible. The result? Your fuel mileage goes down. Depending on your driving style you may only notice a slight loss in mileage to none at all for more mild-mannered members. If you drive harder/faster, you may notice a significant loss of mileage with a dead knock sensor.

So what is the difference on a BUTT-DYNO? I would say EASILY 15-20 horsepower and torque at the crank. There is a BIG difference. I really had to get on it pretty hard just to out-accelerate a 4-cylinder Accord with my knock sensor blown, and that's with a 5spd too.

PARTIALLY WORKING KNOCK SENSOR

There really isn't much to explain here, except to just want you that your car will be extremely annoying to drive because it will not perform consistently.

Even with your ECU throwing a knock sensor ghost code, it could still be on either the default optimized ignition map or the safe map for a blown KS at anytime and without notice. If it is getting invalid readings from your KS it may put the car in the safe map. If it is clear for say 5 minutes, it may put it back on the default "optimized" map until it gets invalid readings again. The result is that when you put your foot down as you're trying to merge and are expecting a certain amount of power to complete a maneuver, you may or may not get it and you could get yourself into trouble! This really drove me nuts commuting through really heavy DC traffic and made me uneasy about my car.

Proof of this is in one of my data logs. At the beginning of my trip home from work I went WOT in 3rd gear and got the optimized 15-25 degree range of advance and the engine felt very zippy with plenty of pull. Yet just 10-15 minutes later I accelerated in the same exact way and got a max of only 10 degrees of ignition advance and there wasn't nearly as much pull. So you never know what to expect. Not an enjoyable driving experience by any means...

My knock sensor has been slowly dying for the past few months. It started out just going into this safe map once in awhile but mostly being on the optimized map. Then it just slowly transitions from that, to about 50/50, to being completely blown and on the safe map 100% of the time. I cleaned up the grounds of the sensor (see http://www.motorvate.ca for reference) and that helped a lot, but only extended the life of the sensor a few more days until it completely died.

BYPASSED OPERATION VIA 470K RESISTOR

If you locate the knock sensor sub-harnass and disconnect it, you can stick a standard 470k leaded resistor into the connector and then tape it into place. Since the "no knocking" resistance of the knock sensor is 470k, putting this resistor in is how you fake out the ECU into thinking that everything is okay as a temporary fix until you can get your knock sensor replaced. This will get you back on the performance (default) ignition timing map and your car will not feel like a slug anymore.

*** WARNING: THINGS TO BE AWARE OF WITH THE RESISTOR "FIX" ***

This bypass resistor fix effectively removes the safety net that the engine has, so YOU are now the "knock sensor" and need to take appropriate action if your engine starts knocking.

Remember above where I said...

Quote:Originally posted by SteVTECAnything from about 30% throttle and up (before the WOT map) should give you somewhere around the low/mid-20 degrees of advance, but it may drop to 18 degrees momentarily. (this observation will be important later)

...???

As it turns out IT IS POSSIBLE TO GET KNOCKING EVEN WITH PREMIUM FUEL WITH THE BYPASS RESISTOR.

Under certain conditions such as very high summer temperatures, or if you have a lot of mods, the default ignition map may be a bit too aggressive and the engine may start knocking. Since the car is now operating "open-loop" (not-controlled) without the knock sensor, there is nothing to tell the ECU to trim back the timing a bit to avoid the knocking and protecting the engine. You need to listen carefully for this and if you get some knocking, determine if it is severe enough to do anything about it.

Running yesterday with my bypass resistor installed, I DID get some extremly mild knocking at about 3400 rpm (peak torque on a 4th Gen) when accelerating moderately (timing still at 20-30 degrees) with the OBD-II scanner reading Intake Air Temperatures at about 95F. If the knock sensor was working and in place, the ECU would have trimmed timing back to about 18 degrees to avoid the knock, and then re-advance back into the 20 degree range. The pinging I heard was extremely mild and nothing to be concerned about. All engines are more than able to take a little pinging and the VQ has proven to be a very tough and durable engine. This morning I monitored everything again, and the IAT read only 80F, 15 degrees cooler than yesterday. No pinging/knocking ("ping" is a more accurate description of the sound) whatsoever.

But my car is stock. If you have a modded Maxima you may get more pinging than me, especially when combined with high temperature heat-soaked conditions. Just monitor this and keep your stereo volume lower and be aware of what could happen. It goes without saying that you should run nothing but premium fuel with this bypass fix. If multiple people drive your car and someone puts 87 in it you could be in trouble. In that case I would probably not even bypass at all, as that is a recipe for disaster. If you live in an area such as California where the highest you can get is 91 octane and it also gets rather hot, you will need to be even more careful. Just be aware of that YOU are now the "human knock sensor".

If you have made it this far and have actually learned something and/or found this information helpful, CONGRATS!!

SUMMARY

Knock Sensor working: Optimized timing map, should never hear any knocking, consistent performance.

Knock Sensor bad but still connected: "Safe" ignition map, cruising performance/mileage should still be okay, but anything above about 30% throttle sends your timing advance (and power) right down the toilet and your car will feel like a slug.

Partially Working Knock Sensor = Annoying as hell due to inconsistent performance and the ECU not knowing which ignition map it should be on, but it's still safe for the engine and you shouldn't get any knocking. Be careful when merging.

Bypassed Knock Sensor: GOOD performance due to ECU being tricked into think you have a working knock sensor. But this is the least safe because the resistor simulates a knock sensor that never hears any knock even if you DO get knock, so you need to be careful. YOU need to become a "human knock sensor". This is not foolproof. You can still get knock even if you are running premium gas, so just be careful.

phweew!!

--Credit: SteVTEC

Link to discussion thread:http://forums.maxima.org/showt...33739

[maxnix]

How does the knock sensor affect timing?

It sends the ECU into base default fail safe mode.

On of the problems in not pulling the mainfold is it and the EGR tube inside do not get cleaned. Along with the IAC valve, this will lead to idle instability, bit I don't know if it will cause your misfire at idle.

Be sure not to miss with the TPS sensor if you do the intake pathe cleaning.