Seemingly unusual Cylinder Misfire(s) in 02 I35

[sib390]

Now I know there are plenty of posts about cylinder misfires and I have spent many hours looking through them but what I have goin on does not seem to be 'the norm'. I will try ot include as much info as possible but I may leave something out so I apologize in advance...so here goes.

I purchased a used 02 I35 with 57,xxx miles on it. For the first few weeks or so it ran great with impressive power at any speed.

After this, it started running really rough. Even when it didnt run rough it obviously lacked the power it previously had. My first thought was "crap, I bought bad gas!" Since the day I bought it I put 89 grade from reputable stations. At times it would idle rough like it was going to stall (but never did) and would occasionally flash the check engine light but not throw a code. After messing around with different grades of gas from different stations it seemed to subside but I seldom had the intense power it first had when I bought it. This secario went on for a few months. Never running great but never throwing a code.

Finally it got to where it ran crappy more than it ran decent and it finally gave a code to go on.

The first code was a P0304 Cylinder 4 misfire. After some research I decided to replace the ignition coil (and the spark plug while I was there). This got me to where it was running OK but not blinking the check engine light. After a week or so, it started up again.

I brought it to the Infiniti dealership. They looked at it and said they couldnt find anything and if it didnt code or act up while they were looking at it, they couldnt tell me what was wrong. After paying the $100.00 I got part way home and it started again with the flashing and threw the same P0304 code. (BTW, I have a scanner) .

I swapped out the coil I put in with the #2 coil. The problem stayed on Cylinder 4.

I took it back to the dealership and after days of investigating, they said, your #4 injector is bad. They replaced it, charged me the $365 and sent me on my way.

ON THE WAY HOME, it started acting up again (SES light blinking)but didnt throw a code. I brought it back to them and they looked at it, supposedly hooked up to it while they drove it and although it ran crappy they said they didnt gather anything to help them diagnose it. They gave it back to me and said until it acts up, we cant do anything more.

I got 2 miles down the road and it started flashing the SES light. (UGH) It didnt throw a code until I was almost home.

This time it referenced P0302 Misfire in Cylinder 2! After wondering if they just swapped out my bad #4 injector with my #2 injector, I brought it back to them again. After 2 days of troubleshooting they said: Ok this time you have a bad coil on cylinder #2. I asked them to just swap it out with the #4 coil to see if the problem followed the coil. They said to me "that would be a waste of our time, the injector is not dry, it is definitly coil #2 that is bad"! They offered to fix it for $260.00. I explained to them that after the $360 dollar injector and the $100 diagnostic fee and still having a problem, I had to think about it before I dropped another $250.

Having actually believed them that coil #2 was bad, I ordered another coil for $50 and replaced it. Low and behold, I STILL HAVE A PROBLEM! The code it is giving is P0302 Cylinder Misfire.

This problem is killing me. Obviously the dealership cant figure it out and I cant continue to drop money on this.

In doing further research, I came across people who get a P0300 Multiple Cylinder misfire and this is sometimes accompanied with a P0011 or P0021. There is actually a TSB (FC9002981) referring to this and suggests there may be an issue with the Intake Valve Timing Control Solenoid.

Is this possible with me? I have never recieved the P0011 or P0021 or even the P0300 with MULTIPLE misfires but I have had problems with Cylinder 2 and 4 and they are in the same bank. I realize it probably sounds like I am grasping at straws but at least when I do it it doesnt cost $200 - $400!!

Some observations:1) Chaning the grade of gas (either up or down) seems to make the problem worse.2) Going up hill seems to bring on (or at least intensify) the issue.3) It happens when the weather is warm or cold.4) If it is running crappy and I turn it off and let it sit over night or for a day or two, the problem still exists either immediately or shortly after starting.

Again, I am not a mechanic but am fairly mechanically inclined.

PLEASE HELP ME!!!

[3Q Jay]

welcome to NICO. good detailed posts are appreciated.what do the service records say about the history of the car before you bought it (if nothing else, now as the registered owner, you are well within your right to get the infiniti performed service history--won't matter where the dealer was, the records will show).what did the plugs look like when you pulled them?what do the injectors ohm at?O2 sensors sometimes throw cylinder misfire codes.make sure you use the NGK plugs. don't think your car came with the double platinums, but you can't go wrong using those.

i would try a can of BG44K (best followed by an oil change).

[sib390]

Jay, thanks for the reply.

The only portion of the history I checked out was if there were any outstanding recalls. Besides that I will have to ask them again.

I replaced the plug in cylinder 4 with an NGK (even though it looked ok) and it did not help the cylinder 4 issue any and this time the plug in cylinder #2 looked like #4 looked, not brand new but in good shape. I havent changed it but I guess it wouldnt hurt.

As far as the injector ohm reading, I have a meter but dont know where\what to measure.min

I havent tried BG44K but I can do that also.

It just seems odd that the problem is now in cylinder #2, that is why I am curious as the valve time solenoid or something related. If the timing is off for a bank of cylinders wouldn'y they ALL be misfiring at the same time?

[Q45tech]

The only method ecu has to sense a misfire is the O2 sensor for each bank of cylinders. The fact that 2,4,6 are the same bank leads me to believe the O2 should be changed along with all sparkplugs.

Previous owners can do a lot of damage with oils and gasoline selection.

Hopefully you or previous owner have not been buying E10 ethanolized fuel.

Coil failure is pretty common...............injectors less so unless ethanolized.

[sib390]

Thanks Q45 Tech. I do not run that type of fuel., although I cant account for the previous owner.

I have a question about the O2 statement... Would a failed Oxygen sensor make the car run like complete crap? In the past the only thing a failed O2 sensor did on my vehicles was trip the light and make them fail an emissions test but never change how it ran.

Thanks for the posts guys!