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Ignition or Fuel?

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Heyoo, anyone have any links to previous discussions or advice on an issue?


My 87 pathfinder with vg30i.

Having very bad misfiring and sluggish engine at low rpms with high loads. It runs pretty fine and dandy above 2,500 as well as cruising at 2,000. Just can't accelerate without downshifting because of sluggishness and misfiring.


Ignition coil was changed less than a year ago, as well as plugs. Wires are fairly new too and the beefier NGKs so I would imagine they're not the issue..

Cap and rotor for the distributor are less than a year old too. Though cap definitely had charring that I've cleaned before and seems to help a bit. Hence me thinking it's ignition, but I don't know what else it might be. Ignition control module?


I've checked all the emissions parts, egr and pcv valves are good.

No 02 sensor plugged in currently but it was doing fine without it before, and mass air flow was pulled off and cleaned.

I haven't tested fuel pump or injectors, but fuel filter is pretty new...

Maybe someone knows something else to check?


Any advice or links to previous discussions is greatly appreciated.



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Sounds like you've covered most of what I'd check. I'm assuming you've also gone over the vacuum lines. If you can borrow a timing light, that might give you some idea--not as much what it's set at (unless the distributor somehow moved on its own), more seeing if it's jumping all over the place or missing beats. I've read you can replace the transistor on the early systems with the later version from the multiport, might be worth looking into if you decide to fire the parts cannon. If it runs well at high RPM under load, I doubt it's fuel supply, though of course that doesn't rule out the computer or injectors doing something weird. How's the idle?

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@Slartibartfast Idle varies up and down occasionally but runs smooth, apart from an occasional hiccup where it'll start idling surprisingly low.

I'm hoping it's not injectors, from what I found online they're a pretty penny. I'm by no means an expert on throttle bodies, but I checked down the intake while running and they both seemed to be injecting just fine. But then again I can't check them when it's doing the thing, so who knows.

Probably will end up taking the throttle body off and cleaning it whenever I have enough time or can get the backup vehicle running again


I have a lot of electrical gremlins in my dash that I'm 75% sure are stemming from a bad ground somewhere. So maybe that could be something too? Gotta read through they Haynes book and decipher wiring diagrams eventually.


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An update! Whilst checking plugs this afternoon, I accidentally broke one. This lead to a replacement of all 6, and the realization that my brother had gapped the plugs too short waaaayyyyy back before the covids when I had changed them last...
And lo and behold, the issue seems to be resolved.
For now!
Moral of the story, don't let someone who was probably drunk at the time gap your plugs.

There's still an issue of excess arcing in the distributor cap. Which might be the ICM, which I have a new one coming.
So Rejoice! I don't have to take my throttle body apart. Just yet at least.

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  • 3 weeks later...

The cooling fan getting stuck on (failure of the centripetal clutch) is a common problem, and it sucks up a lot of power, which is noticeable at low RPMs. 
Over 20 years and 300,000 miles, I've had two of them fail on me. 

It's one of the first things that I check when I'm having sluggish performance.

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