STILL misfiring! Tried everything. PLS HELP!
 

Hey guys, I have a 2004 Infiniti G35 Sedan and for a few months now, it has been misfiring.
Before anyone tells me to go and look at other forums, I want you to know that I have spent the last 3 months clicking different threads and reading everything.

That being said, this is what I have done so far in order to try to fix the misfire:
1. At first I thought it was octane ping, so I added some octane booster. (The car had been running sometimes 93 and 89 octane.) It helped the car a little bit.
2. After that didn't fix it, I installed Bosch Spark plugs from autozone. Again, it obviously helped the car overall, but didn't fix the misfire.
3. I bought a code reader and showed me that it was cylinder 5 was misfiring. So I swapped the ignition coil with a different cylinder, still misfiring. I did the same thing with the fuel injector.
4. Also, I installed a new pcv valve.
5. Today I installed a new crankshaft positioning sensor. Still nothing working.

Now let me point out, My engine has the typical vq35de issues. I found oil in the sparkplug holes. So yeah I know that it's the seals and that the only way to fix it is by buying new valve covers or going with a DIY option.
There was also a lot of oil in the plenum. I tried to clean as much as I could, Including in the well, where oil was pooling. (I installed the pcv valve after I saw this.)

I also used a bottle of Royal Purple Max Clean, (knowing that it may harm the O2 sensors), and sure enough I got 3 new codes. "Heated O2 sensor", "Heated O2 sensor", "Bank 1 O2 sensor slow response". **
**I know that maybe I shouldnt have done this, but it was done when I thought that maybe the injectores needed to be cleaned, or the gas needed a higher Octane amount. The car misfired before and after the royal purple.

Okay so as far as the actual misfire goes, It does not misfire until I'm past 50% on the throttle. So when the car is pulling a heavy load. Casual driving is fine. I can go to the redline slowly. Which makes me think it may be something with the throttle body? Idk.

Also, the car does that hesitation when stopped. I'm not sure if that is related to the misfire, or if that is just some vacuum leak. I am not sure.

This issue has frustrated me so much and I would love if anyone else has anymore ideas or suggestions. Thanks in advance. I have read and seen how helpful people are on this forum.

Did reading everything include reading the FSM?

Do you expect it to fix itself?

No it didn't!

Keep throwing parts, perhaps you'll eventually replace them all?

Do some more reading

http://www.nicoclub.com/service-manu.../Sedan/2004/ec

See page EC-286

The misfire detection logic consists of the following two conditions.
1. One Trip Detection Logic (Three Way Catalyst Damage)
On the first trip that a misfire condition occurs that can damage the three way catalyst (TWC) due to overheating, the MIL will blink.
When a misfire condition occurs, the ECM monitors the CKP sensor signal every 200 engine revolutions for a change.
When the misfire condition decreases to a level that will not damage the TWC, the MIL will turn off.
If another misfire condition occurs that can damage the TWC on a second trip, the MIL will blink.
When the misfire condition decreases to a level that will not damage the TWC, the MIL will remain on.
If another misfire condition occurs that can damage the TWC, the MIL will begin to blink again.
2. Two Trip Detection Logic (Exhaust quality deterioration)
For misfire conditions that will not damage the TWC (but will affect vehicle emissions), the MIL will only
light when the misfire is detected on a second trip. During this condition, the ECM monitors the CKP sensor signal every 1,000 engine revolutions.
A misfire malfunction can be detected on any one cylinder or on multiple cylinders

Good luck

Telcoman

Pull out all spark plugs, they should all look the same, if cylinder 5 still looks bad then you have ruled out the coil pack/injector/spark plug because you swapped it all with another cylinder right?
Check the entire engine for vacuum leaks.
Check the HARNESS of the injector and coil pack.
Compression test the motor, cylinder 5 might be almost dead. There should be no more than 10% variance between the highest and lowest compression cylinder. Make sure to pull your fuel pump relay before doing the compression test...

Thanks for the response guys. Will do more reading and pull the spark plugs.

I just finished the compression test and it seems that I got around 135 psi on all cylinders. Any guidance on if this is good or not? I was hoping cylinder 5 would show a lower number, but it did not.
Thanks

On my old old Honda years ago..
Fuel pump was bad and wasn't sending the right pressure upfront and threw a misfire code...

Then a maf sensor went bad and throw more misfire codes..

When you look up one code it can have up to 5 different causes:icon30:

Don't know if that helps at all

Intake manifold causes misifires too

Misfires are 81tch3$

Not sure if you're still having this issue but 135 psi is VERY low compression, I think the FSM suggested 185psi as standard compression with the low limit being 140psi. Try putting 1 TBSP of oil in each cylinder and try it again, if the numbers jump substantially then you're due for a rebuild. Also make sure you did the correct number of revs of the motor, I think it needs to turn over 7-8 times.

You did the compression test on a warm motor correct? If you didn't then you need to do-over, make sure you have anti-sieze on the spark plugs, don't immediately pull them out either, let the motor cool for 15min after driving (by the time you get everything disassembled after running).

Thanks for the replies. Ive had signs of failing fuel pump, so im going to go ahead and replace it.

At my whits end😧
 

Did replacing the fuel pump do anything for your misfire i currently am plagued with cylinder 4 misfire and have replaced the same you have ??!!

Air intake?
 

Does it misfire from the air intake? Bec I have the same thing that u having

I have the same problem with the same cylinder 4 what is the problem need help

ignition coil

are you saying the ignition coil was the problem?

so all the ignition coils were bad? Did you replace with oem?

weak *** explanation