I know this isn't specifically an all motor problem, but I didn't get much help in the general forum so I figured I would repost here with some more information since the quality of minds is generally higher in here

I've done my searching and have done the basics but still haven't been able to locate my problem so I come to you for help. BTW, I have a 2001 DEK motor in my car.

It started about 2 months ago. One day while driving I noticed that my car, more specifically the engine, vibrated/shook around 2500 rpm. The sensation was greatest in 2nd gear. I think the vibration continues up the rev range, but it increases with speed so at 5000 rpm the vibration is so frequent that you almost can't feel it. I haven't noticed a power loss or the problem getting worse over time. My A/F ratio is still 14.7 at idle and around 12.5 at WOT. The car seems to start and idle fine as well.

The car isn't throwing any more codes that usual (a Maxima ECU in an I30 will do that).

I started by replacing my old copper NGK plugs with the platinums but that didn't do anything.

I went for a drive with my mechanic and he was able to monitor the wave forms of the two front O2 sensors and the wave form of the front (bank 2) sensor was very off under load. The sensor itself is probably less than 2 years old and didn't give any indication that it was bad, so we believe that problem lies in the front bank. At first he drove the car himself and couldn't get it to recreate the vibration, but then I took him for a drive and from the passenger seat he said it felt like a misfire.

I know that coils are a common problem in these cars so I got one front and one rear new coil pack and switched them around the cylinders but the vibration remained.

The only thing I can think to do now is replace the KS. If that doesn't do it I'm going to be very frustrated and confused. What else could it be, maybe a bad injector? How could I do a test for that?

I should note that I'm pretty religious about scheduled maintenance. Oil every 5k, 93 octane gas, new fuel filter, clean throttle body, all O2 sensors have been replaced, etc....

First update: My car finally threw a code aside from the usual 8, for a B2S1 O2 sensor. I put a new one in, the code is gone, but the hesitation remains. This probably explains why my waveforms were acting up when we did the datalogging. We have not done any datalogging since though.

Second update: I think I may have narrowed down I feel the vibration the most. At 50% throttle in 2nd gear at 2000 rpm to about 3000 then it tapers off. Also, I believe my AFR has gone rich on me as I saw it at 12.0:1 at WOT when it used to be 13.0:1 at redline. Could this be a leaky injector?

I also noticed that after putting in the stock ECU, my car ran richer than with the JWT ECU. Is this normal? I have a Nismo AFPR and Walbro FP because I used to run nitrous, but since I've removed all of my nitrous stuff I'm thinking about getting new OEM FP and FPR to simplify things and eliminate variables. Too bad a new FP and FPR are like $500.

In the original thread someone mentioned doing on ohm test on the injectors, are they should be between 11-14. Is this correct? I haven't done this yet, but aside from that and a fuel pressure test, I'm out of ideas.

So, has anyone dealt with something like this before?

 

What injectors do you have?

I'm thinking it is a bad coil/injector. Check the FSM for ohm specs on the injectors.

Have you cleaned the cam/crank sensors?

 

I have DEK injectors.

Since I've tested all new coils on all 6 cylinders, I would like to think I've eliminated that as a variable. I did only drive on the new coils for a few minutes on each cylinder, but I figured that was enough to see if one was bad.

I haven't cleaned the crank sensor but my cam sensor is less than two years old.

 

Are they grey dot coils?


Def clean the crank/cam sensors, takes ten min and i bet there is a bunch of shavings/oil/crap on them. Not sure it if it will fix it, but it might.

 

Im going to take a guess and say you dont have access to a scope, correct? If you do, scope the cam and crank sensors after cleaning them, as well as the coils, and injectors. If you had a leaking injector, it would probably present with rough starting issues as well. A stuck injector could cause a misfire.

 

I work at a garage and we have some expensive SnapOn and Bosch tools, it's just a matter of getting the qualified mechanic to get some time and do some datalogging when I'm driving. The car starts fine, and it might just be my imagination, but it seems to run very slightly rough for the first minute or so in the morning. I don't hear any knocking or misfires when driving though, or I might just not be aware of them.

I know where the cam sensor is, but not the crank. Is that just lower down on the front/PS of the motor?

Should I just clean the cam and crank sensors with alcohol?

I don't see any gray dots on my coils...where would they be, and if I did have them, what would it mean?

 

http://forums.maxima.org/5th-generat...ow-w-pics.html

There are pics in there of the F/R coils with grey dots.

Grey dot coils are what you need, try to find them.

 

Do you have a Verus or Modus? Anything with a lab scope. We have a verus at the shop and we use it all the time to diagnose electrical issues.

Just out of curiosity, what EGR and IAC setup are you running?

The crank sensor is right next to the crank pulley on the front of the engine. I would try finding some of those coils first, however.

 

what happens to the AFR when this problem occurs?

 

The mechanic with the Verus left so I think we just have the Modus now.

IIRC, I'm using the 4th gen EGR and PF IACV.

Well like I said it happens most noticeably at part throttle, so I'm not sure what my AFR is supposed to do at part throttle. I know it's supposed to be 14.7 at idle and 12.5 at WOT, but really don't know about part throttle.

Before my WB O2 sensor started acting up I did a test at WOT (with JWT ECU) and found I was hitting about 12.0 instead of my usual 13.0 at redline at WOT. When I put the stock ECU back in it went down to 11.0 at redline. So it looks like I'm running rich right now at WOT. Why would my AFR change so drastically between the two ECUs?

I guess I'm going to test the coils today with the multimeter. Can I do a similar test for my injectors?

 

Might want to see on the data logger what the IAC is doing during partial throttle. If you're running lean, that might be to blame.

For the injectors, you should read between 13.5-17.5 ohms at 68* F. Also, here is a printout for checking the injector system.

https://docs.google.com/viewer?a=v&p...5ODJi&hl=en_US

 

Ok I checked the coils with my MM set up as shown:



But the results don't match the pattern shown in the coil thread. They are as follows:

Coil 1
+1 –2 1.60
+1 –3 I
-1 +2 1.60
-1 +3 I
-2 +3 I
+2 –3 19.27

Coil 2
+1 –2 1.58
+1 –3 I
-1 +2 1.58
-1 +3 I
-2 +3 I
+2 –3 19.37

Coil 3
+1 –2 1.65
+1 –3 I
-1 +2 1.65
-1 +3 I
-2 +3 I
+2 –3 19.12

Coil 4
+1 –2 1.63
+1 –3 I
-1 +2 1.63
-1 +3 I
-2 +3 I
+2 –3 19.26

Coil 5
+1 –2 1.63
+1 –3 I
-1 +2 1.63
-1 +3 I
-2 +3 I
+2 –3 19.58

Coil 6
+1 –2 1.59
+1 –3 I
-1 +2 1.59
-1 +3 I
-2 +3 I
+2 –3 19.69


From the coil thread, it looks like his normal pattern was something like this:

+1 -2 1.51
+1 -3 6.8
-1 +2 1.51
-1 +3 I
-2 +3 I
+2 -3 6.25

Since all my coils tested the same way, I'm going to assume they're all fine, but I don't understand why their pattern is so different than what was in the other thread.

I'm looking in my Haynes manual and I want to test the resistance for the injectors, but I don't know which setting I should have the MM on, can anyone tell me?

Ok, reading through the manual for the MM it says to test resistance at the 200k setting, but when I did this I got a reading of 0. At 20k it was 0.02 and at 2000 it was 16. How the frick do I use this thing?

 

Haha basically, your multimeter isnt "auto ranging". Meaning you have to select the "range" at which it will read. Everything in the bottom left side is the Ohms reading (resistance), which you already knew. Basically the 200, 2000, 20k numbers indicate the upper limit of the reading range. I.e. if you want to measure resistance between 0 and 200 ohms, put the meter on 200, if you want to read resistance between 0 Ohms and 2000 Ohms, put it on 2000.

If your meter reads "open" or "infinity" or "overload" (meaning an open circuit), turn meter to a higher range. Basically, if you're testing from 0 to 200, and your resistance is in killaohms, your meter will see an open circuit, until you turn it to 20k.

For testing the injectors, you'll want it on 200. Look for numbers between 13.5 and 17.5. You can probably test this at the PCM connector, since you cant access the right bank injectors from under the UIM.

 

On a side note, might want to try one of these meters:

http://www.google.com/search?q=auto+...w=1680&bih=899

Basically they will read "245.xx" and then next to it say either "Ohms" or "k Ohms" or "M Ohms". It "auto" changes the range in which it reads. I use an OTC 750 series for work.

 

So for the coils was 20k the right setting, or should I set it to the 200k for the +1 -3, since that's the one that's different between my test and the test in the other thread?

How would I do the injector test on the PCM connector? I don't understand that part.

-------

Ok, I did the full coil test at 200k and two of my rear coils are reading differently than the others.

At 200k

Coil 1
+1 –2 I
+1 –3 I
-1 +2 I
-1 +3 I
-2 +3 I
+2 –3 122.7

Coil 2
+1 –2 1.6
+1 –3 123.4
-1 +2 1.6
-1 +3 I
-2 +3 I
+2 –3 121.3

Coil 3
+1 –2 1.6
+1 –3 123.2
-1 +2 1.6
-1 +3 I
-2 +3 I
+2 –3 121.2

Coil 4
+1 –2 1.6
+1 –3 122.7
-1 +2 1.6
-1 +3 I
-2 +3 I
+2 –3 120.4

Coil 5
+1 –2 I
+1 –3 I
-1 +2 I
-1 +3 I
-2 +3 I
+2 –3 123.2

Coil 6
+1 –2 1.6
+1 –3 125.5
-1 +2 1.6
-1 +3 I
-2 +3 I
+2 –3 123.1

Coils 1 and 5 are only getting readings at +2 -3, which leads me to believe there might be something wrong with them. If two are actually bad, it might explain why replacing 1 rear coil at a time didn't solve the problem. And I suppose an incomplete spark could also cause the car to run rich.

But of course I really have no idea what I'm doing and today is the first time I used this multimeter, so I could be messing something up. I did triple check my readings at 200k and they always came back the same, so I'm thinking I'm doing it right.

I also tested the front injectors and they were all between 15.5 and 15.8, so it looks like those are all fine, but I'm unsure of testing the PCM, can anyone help me out on that?

 

Ok, so I went back and tested them all again at 20k and now I'm really confused. Coils 2, 3, 4, and 6 all read the same as the first time, except all read I for the +2 -3 setting, while they read around 19 the first time. Now, coils 1 and 5 read I for all 6 tests, when they were identical to the others the first time I tested. What could cause the change in resistance over a few hours? Either way, both tests now show coils 1 and 5 to be different than the others, I just don't understand why that didn't show up the first time I tested them and why the others have changed their reading for +2 -3 from 19 to I. What gives?

Also, what's the reason for my numbers being so far off the numbers the guy got when he tested his coils?

 

Not sure why your numbers are so far off, but yes I might conjecture that you have an issue with 1 and 5.

The different readings you got might be due to temperature. Could be a few things, to be honest.

Im not sure what setting the meter should have been on, it depends if you're looking for ohms, k ohms or m ohms.

 

I was ready for this to be a glorious post about how I rejoiced when I took the car for a drive after putting in the new coils for 1 and 5.

Nope.

Not a god damn thing changed.

In fact, when I tested the bad coils after taking them out, they both read just like the others! Then I tested them again a few minutes later and one read bad and the other still read normal.

I then tested 3 after the drive (it was hot) to make sure I hadn't confused it with one of the bad ones and it tested fine, although the numbers were way off what I got for it yesterday. I'm gonna go out on a limb here and say that the temperature and duration away from the car somehow affects the resistance. How? I have no idea. I'm going to test the two bad coils again and see if the other goes bad again after being out of the car for a while.

I'm going to get all new coils tomorrow for the hell of it and see what happens, but I have a feeling it won't make a difference. At this point I'm starting to lose hope or think the problem is coming from my transmission, as I first noticed the problem after replacing an axle that had blow its carrier bearing and I drove on it for a few miles.

Dear lord....please help me....

 

Temperature does affect resistance. Also, on a note, if your fingers are touching both of the test probes, you will throw the numbers off. Be sure that the test lead metal only touches the pins on the coil.

 

Well I'm holding both of them but I'm not touching the metal at all

 

Okay youre fine then. Your body has resistance, so touching the leads can fubar with resistance readings.

I asked my boss about a possible tranny issue. He said if it was internal, it would make noise with a vibration, not just the vibration. I had a car the other day that only vibrated at high speeds, low rpm, only upon acceleration. I thought it was an axle, but my coworker thought it was a tire balance issue; not sure what it ended up being, didnt drive it after. That being said, might be something to keep in mind.

 

Don't know if this was mentioned yet, but do you have a Fidanza flywheel?

 

Nope, resurfaced OEM.

I bought the other four new coils and I'm testing them right now before I throw them in the car. Somehow one of the coils that repeatedly tested dead on Sunday is now repeatedly reading normal

 

Well now I'm more confused than ever. I tested all the brand new coils and the resistance pattern was different between the front and rear coils. All three fronts had the same pattern and all three rears had the same pattern.

I put all the new coils in the car and went for a drive. The vibration remains. I spent the next 20 minutes trying out different speed/gear combinations to narrow the problem down. I can get the car to vibrate in any gear, but only between 20-35 mph, and I *believe* only when I accelerate. I originally thought the problem was most pronounced in 2nd gear, but that's because it's the gear I'm usually in when accelerating between 20-35 mph. I could get 1st and 3rd to both vibrate as well, but only when accelerating between those speeds. 2nd gear above 40 felt normal as well.

This leads me to believe this is a tire balancing problem, although I've never experienced one rearing its head at such a low speed, and then only when accelerating. The car pulls and cruises smooth on the highway.

On another interesting note, after replacing the two rear coils that originally tested bad, my AFR at WOT at redline remained at the rich 12.0:1 it had been earlier. Today, after replacing all 6, it was back to its normal 13.0:1. I'm so lost at this point.....but I'm going to rebalance and rotate my tires tomorrow before I make my trip to 2JR to get my panhard rod installed on Saturday

Edit: I'm going to experiment with different gears and acceleration on the highway tomorrow and will monitor for any vibration while cruising off the gas between 20-35.

 

Check all of your tires. Had a BMW today that had a slight shimmy/shudder only around 35, at partial throttle. Rear tire was separating.

 

If you are getting vibration on acceleration check the front and rear motor mounts and axles.

Had a 6 speed 5.5 gen come in with a busted rear motor mount and the steering wheel shaked on accelartion in the lower gears. But at cruising speed it was normal with no vibration.

If its not mechanical I would say check the fuel injectors. A bad or mis-matched injector can cause alot of annoying problems with driveability.

 

I've got hesitation and what feels like power loss at low rpm as well. Also have dek injectors.
When taking off in 1st, I would get to 1800rpm and it would start hesitating, struggling, like something is holding it from accelerating, then it would stop and be normal.
It's not the coils or injectors. I've never actually tried to track it down as the motor has internal issues and it would take too long. I'm thinking of resetting the AFC to see if the afr is culprit.

 

It's funny you mentioned that, we just had the wheels off to balance them if necessary and when we put one of the rear tires on the machine it looked like the wheel was super bent or the belts had separated inside the tire because you could see the tire shape change as it spun. We're going to check it again in a bit.

Also, one of my front LCA ES bushings has kind of squished itself out from its hole a little but. I'll try and post up a pic in a bit.

Well we've done the motor mount rock test and the ES mounts are all keeping the motor in place. The PS axle was the one that replaced the one with the busted carrier bearing. I didn't notice this problem until after I put in a used PS axle from a friend, but the vibration remained after I put this new one in as well, as my friend's had a busted boot.

I checked the resistance of the front injectors already and they were fine, but I don't know how to check the rears without taking off the IM.

BTW, it looks like I'll be seeing you on Saturday at 2JR!

Yeah, problems like this are quite annoying and difficult to track down

 

You can check the rear injectors at the pcm by back probing the wires that come from each injector. You'll have to look on a wiring diagram to see what's what. Basically instead of checking them at the injector, you're using the engine harness as a giant wire extension.

 

Joe, check your PM!

Update: My rear tire isn't coming apart, I just have a very bent wheel. Oh well.....

 

Ugh, I think I need to bump this thread

Well after a full year or so of chasing this vibration, I'm no closer to solving the problem. Here is a list of everything I can remember doing over the last year or so:

-new spark plugs
-2 new OEM coil packs, tried all 6 new at one point
-tried a new MAF
-new knock sensor
-cleaned EGR valve
-new PCV valve
-new clutch and flywheel, different trans and both axles
-different sets of wheels/tires
-new ES motor mounts and poly trans mounts
-new fuel filter, fuel pump and relay
-different ECU
-new/cleaned injectors
-new CAI, headers, cat back
-out tie rods, wheel bearings, hubs, all bushings, alignment, coilovers
-all brakes



At this point I'm pretty sure there is something internally wrong with my motor. I'm thinking either a bent valve or valve float, since I do rev the car to 7000 pretty regularly. My only ideas at this point are to do a compression and leak down test. Does anyone else have any ideas for me?

 

Did you ever perform the leak down test sir? I hate to say it but this sounds like a head gasket.

 

If this were a head gasket I would have coolant in my oil and I would be losing coolant. Neither of those are happening, so I don't think that's the case.

As a matter of fact, I think I tracked down the cause of this last weekend.

The long and short is I think my lightweight UR crankshaft pulley is causing the vibration. The motor just pulls too hard for there to be something wrong internally, and it really does just feel like it's out of balance, which is exactly what a bad crankshaft pulley can cause.

So we tried to take off the UR pulley, and guess what? Even with the biggest Snap-On air impact connected to the upgraded/bigger air lines and pushing 1,100 lb/ft torque in reverse, the nut holding on the pulley would NOT come off. I can't remember who installed it (not myself) and I don't know if they were just evil and put red loctite on the bolt or if they just torqued the hell out of it, but it is not coming off. And the fucked up part is that I'm pretty sure this thing is the cause of all these vibrations! The only thing we can try at this point is to hit that bolt as soon as I pull my car into the garage and hope the heat in the engine will help it loosen, because we can't use any penetrating lubricant and we can't use a propane torch....so that's the last step before I either accept my problem or throw in a 3.5

 

Yeah, you're right about the oil/coolant... not sure why I didn't put that together . As far as the bolt goes, I've had quite a few get stuck on me and I've always taken an 18" breaker bar w/an impact socket and used the starter to break the bolt. Put the bar/socket on the bolt, aim the breaker bar towards the front of the car, put some wood blocks under the breaker bar, and hit your starter for a couple seconds (no longer... don't want to burn the starter out). On my Max the front end will lift a bit and then the bolt will come right off. My air compressor is big but only capable of 125 psi so I've always had to do this.

GOOD LUCK, let us know if the pulley fixes your car!