‘98 VG33 specific cylinder misfire

[UpUp_Away]

I have a ‘98 Qx4 that I should probably sell or junk and just get a new car, but I grew up with her and it’s hard letting go. The latest issue that’s popped up is an intermittent p0305 code. The engine runs smooth, I can’t even feel the misfire, but occasionally, after about 100-200 miles, the code will pop up.

 

I did a replacement on:

 

-new AGM battery

-new spark plugs

-new spark plug wires

-distributor rotor and cap

-ran two consecutive tanks of Techron concentrate and then Redline fuel system cleaner

 

The engine runs even smoother than before and I figured I solved my issue. But about 200 miles later of constant commuting, as I was on the freeway, I saw the CEL come on, and sure enough…

 

Anyone have any ideas on the next step? What could be causing a misfire that I can’t even feel, on a specific cylinder?

 

Because of the new wires, plus, and other parts I don’t think the spark is the issue, although I can try to close the Gap a bit to get a more reliable consistent spark.

 

With the back to back cleaners I don’t know if the fuel injector is the issue either…

 

Attached are the photos of the freeze frame data

 

 

 

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[onespiritbrain]

Go to junk yard and pull a whole new distributor out of an old nissan quest minivan (the pathfinders are always raped down to the frame). Might grab the HO alternator while your there too. 

 

If you still have misfire issues afterward then you can dig deeper.  

[deltaR50]

id pop the distributor open and inspect the dizzy bearing. that can cause that issue as well. i had the same issue. changed the cap and rotor but the misfire was still there. i open the dizzy and found the bearings were worned out and destroyed

[UpUp_Away]

Go to junk yard and pull a whole new distributor out of an old nissan quest minivan (the pathfinders are always raped down to the frame). Might grab the HO alternator while your there too. 
 
If you still have misfire issues afterward then you can dig deeper.  

I just changed the distributor 3 years ago with an absurdly expensive OEM hitachi one.

I’ll double check the timing on it, and also check the bearing as well


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[UpUp_Away]

id pop the distributor open and inspect the dizzy bearing. that can cause that issue as well. i had the same issue. changed the cap and rotor but the misfire was still there. i open the dizzy and found the bearings were worned out and destroyed

Was your misfire to a specific cylinder?

Too bad hitachi doesn’t make the distributors anymore. What would be the next best reputable brand?


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[Strato_54]

I went with the BOSCH cap on rock auto. Its a brand I know, and so far has been working fine. Same quality I would say as the cap that came off it or better. I think I saw a bosch brand distro when I talked to my local parts guy about other caps. Didn't have the cap in stock.

Edited July 30, 2023 by Strato_54

[The_Q]

try a compression test if you haven't already, results could be informative! also, when was timing belt done? unlikely to cause a misfire, but if the belt is stretched, this could be the last of other factors contributing to misfire. The difference in short term fuel trim from bank 1 to 2 is also insane lol (difference of 30% !!!). assuming you were holding the throttle constant while taking the photos, it's possible cylinder 5 injector is not working correctly and the system is increasing fuel to bank 1 to compensate. could be a faulty injector or wiring if it is the injector.