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95 VG30E bad misfire, ideas?


tmoore4512
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Hey guys, been a 'finder owner for a long long time. Had an issue the other night that has me scratching my head.

Utilized the winch for the 1000th time, and when I did the engine quit. Basically every time I would spool in or out, while the truck was idling, it would die. Popped the hood, and held throttle to around 3K RPM and completed the task. Noting that at times it would sound like it was going to die, so I would have to adjust throttle to compensate. Put everything back to normal and all was well.


A few days later:

Vehicle was running superb as usual, came to a stop at a traffic light, took off and she stumbled, and began to back fire and idle very rough if I pressed on the accelerator. I could barely make it to 25 MPH and found a parking lot. Popped the hood and checked everything I could, nothing out of the ordinary.

It had been since the last oil change that I had run a seafoam treatment, and once I limped it home, I did the "through the intake" treatment as I usually do. Only this time I noted that the driver side exhaust manifold was leaking seafoam to the ground. Telling me that either a valve seat is bad, or worse.

Where would you start? Suggestions?

Next day off I am going to do a compression check, and go from there. Really feel like it is a valve issue, but I value the input from several of the veterans on this forum, and welcome your responses.

I don't "mud," cross rivers or bodies of water. Most of my driving is on road, and occasionally off road to a job site, but dust is the only enemy. I work out of this truck, and it has been very dependable.

I regularly service the vehicle, and talk nicely to it all the time. I mean just the other day we had a candle light dinner, and watched Netflix.

Any help will be appreciated.

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Valve issue shouldn't bog the vehicle out like that. Sounds pretty intermittent. I would be looking more towards sensors and electrical.

 

If it were me, I would probably go through all the wiring first and clean / tighten all the connectors. Push the female sockets closed a bit so the pins fit tight again.

 

Sounds similar to an issue I had on my 240sx when my maf connector plug started to get loose at the pins. Sometimes these old girls just need a good clean so all the electronics can talk properly again. Worth a shot and it's free.

 

Would also check ecu codes and run a compression test - first dry and then wet to confirm the engine health.

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Also I wouldn't advise seafoam as a regular use item on an engine. Especially one that may have dust buildup. All it does is force all the junk through the engine and cam end up doing damage if it breaks loose a big chunk or carbon or washes a bunch of dirt through.

 

As laborious as it is, best to pull the plenum snd clean it by hand. It can be done in a day or at the least a weekend. Then you can clean your iacv, egr etc individually and re gasket the plenum. It solves so many little nagging issues these old girls may develop

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Check sensors like the o2, and coolant temp. And the maf wiring is notorious for causing Intermittent issues like this.

 

Don't use sea foam it is a waste of time. How would you notice it Leaking out of the manifold? Only if it is cracked or leaking I guess.

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Exhaust? It still shouldn't be leaking seafoam, just exhaust gasses and sucking air...

Obviously fix that first before chasing other things.

 

 

I don't "mud," cross rivers or bodies of water.

Utilized the winch for the 1000th time, and when I did the engine quit.

:scratchhead:

 

 

Basically every time I would spool in or out, while the truck was idling, it would die.

Sounds like the alternator is failing, or you just need to upgrayedd to a Maxima or Quest alternator.

B

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Been working out of the truck, using winch for pulling wood, rock, etc.

No mud, river crossings or anything like that. I did...but no more, been several years.

Maxima alternator was swapped about 4 months back, could be defective...

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  • 2 weeks later...

Alternator is good to go, battery is as well.

Did some digging, and I believe the TPS is bad.

With it unplugged it acts exactly the same as it does with it plugged in.

More testing to come.

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  • 3 months later...

Sorry for long delay...life has been wild.

TPS was bad, replaced it. Problem persists.

I am leaning towards MAF, but I have yet to see a CEL or a code for this. After I get home this afternoon I will check it out...

Hope all is well with you guys.

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Okay I am back,

The problem persisted once the motor warmed up to operating temperature. Prior to that the issues were pretty non existent.

Here is what I did after tracing and repairing rat chewn wiring. (Jacklegs!):

Removed MAFS, and alcohol/Q-tipped it. (It was pretty nasty).

Determined which wire in the harness was the ground, cut stripped and soldered/heat shrunk...and tied to known good chassis ground...

Holy mother of sweet baby Jesus, it is running better.

Still has a slight miss at times, but what can I say....at least it will idle and drive!


I proceeded to spray down the engine bay with degreaser and rinse it out...rats had made quite a mess and there was some sap and other residue built up....

Runs good for now. Will address the miss next RDO. But at this time...at least it is not going to the junk yard.

Thanks for all the input guys.

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Here I am again....sobbing uncontrollably.

Went out and started the pathfinder, let if warm up....then the oldest boy and I went for a very VERY short test drive.

Dang thing is doing the exact same thing.

Stutters and hesitates if I try to accelerate anything more than VERY SLOWLY.

Absolutely ZERO codes, and no CEL.

It is doing the exact same thing it was doing from the get go.

I am now...at a loss.

Is it beer thirty?

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I need to add...that it runs great prior to getting to operating temperature...

Stupid question...but does the 95 ECU take a serious signal from the temp sender and allow it to affect fuel curves?

Its almost like it is not putting enough fuel to the air ratio (throttle plate open), or maybe it is a leaky injector...dumping too much fuel?

Frustrated to say the least.

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Yes it does. Unplug the o2 and re test. If no results. Try unplugging the coolant temp sensor (yellow plug one in by the distributor). There are also tests in the FSM.

 

This is exactly what my truck did...

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The ecu does get a signal from the temp signal. As the engine gets hotter it increases the fuel.

It almost sounds like an injector issue. Didn't you say you had issues with rat chewing up wiring?

 

You can check the injector cycling by turning the ignition on, pulling the dizzy out and spinning the dizzy gear to verify the camshaft position sensor along with the injector function.

 

Next guess is a vacuum leak issue. Lol. I had a similar thing happen. Engine runs fine when cold it once it warms up it misses and stumbles. I found out that one of the vacuum hose going to the carbon canister was not hooked up.

 

But this doesn't explain the intermittent issue.

Edited by Cuong Nguyen
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  • 4 months later...

Just an update...

No stored codes in the ECU.

Vacuum lines are all in tact...and replaced, as of yesterday just to be sure, some were dry rotting anyway.

Disconnected O2 sensor, it got worse, back to the same when reconnected.

Temp sensor did nothing....hmmm...

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  • 4 weeks later...

It is next on the list! Planning on pulling all six and rebuilding them with new screens and O rings anyway...,for $20 bucks, I cant beat that. Besides they are relatively easy to pull...

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