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 borrowed a coil pack and switched it around the front 3 cylinders but the vibration remained. Now there's no guarantee this coil pack was 100% perfect since it is used, but since the vibration remained identical to before, I'm going to assume I've ruled out the coils.

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?

Edit: 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....

 

There 3 more coils in the back check those. If not check the MAF, that might be bad also.

 

ohm the injectors, they should ohm 11-14

 

Update:

I got new coil packs for front and rear, tested them out, and nothing changed.

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.........I'm really getting tired of this POS.

 

I have same issue. When im at 4k, car smooths out and accels like it should

 

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?

 

Did you ever solve this, if so what was the cause. I have a simular problem. Thanks.

 

No not yet on mine. I am getting ready to order my coils. I am up in the air to go with aftermarkets with life time warranty for a qtr of the cost of oem. The front three on mine is def not the problem.

 

OP: Check this thread out and let me know what you think. I read your post and the amount of DEK folks I see/hear about with this problem are MANY.

http://forums.maxima.org/5th-generat...hile-gear.html

I have NOT yet figured this one out myself; I am really hoping that someone does as I think these could all be related, if not the same issue. Check it out.

 

What are you talking about? He wasn't talking to you.

noahrexion- I read the thread and that sounds a little different than what I'm feeling. The vibration doesn't go away if I give it more gas, it just increases in frequency. It also doesn't make a sounds "like I'm hitting the rev limiter". I'm pretty sure what I'm feeling is an out of balance crankshaft pulley, which I unfortunately can't remove.

 

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