1995 SE cold start OK, misses and will not start when warm.

You gotta Love these old VG30E/i powered beasts, raw truck DNA to the core.

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shaggy
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1995 SE cold start OK, misses and will not start when warm.

Postby shaggy » Tue Sep 22, 2015 4:36 pm

Hi guys
I need some help fixing my old Pathfinder (SE-V6), which has 210,000 miles on the clock and ran very reliably until a couple weeks ago. The problem is it starts OK cold, but develops a progressively worsening misfire which begins at around 2400 rpm once the engine is warmed up and/or the vehicle is driven a few miles. Then she stalls and won't start again until the engine is cold. Now and again it will start (barely) when still warm, and then the misfiring is instant and very severe.

The fuel pump runs at turn-on and primes the system as it should. I've checked the fuel pressure at the rail, and it's normal.

I've changed the ignition coil, plugs, plug wires, the dist. cap and rotor, the O2 sensor, the fuel filter, air filter, oil, and oil filter.

I've cleaned and checked the output of the MAF sensor, also the throttle rotation sensor, checked and charged the battery and cleaned all the electrical connections and vacuum hoses I could see.

I also checked the coolant temp. sensor against a new one and it seems to be fine. The engine has never overheated or burned oil.

Other things: There is a rattle in the vicinity of the AC compressor; the exhaust system around the cats looks very rusty, and the exhaust note sounds a bit too 'open' as if a cat might have broken up (this noise despite a new muffler just a few weeks ago.)
(Could all this be caused by a bad cat?)

The ECU fault code mode III sometimes reads 34 = 'detonation sensor', but that seems to have stopped. Recently it's also shown 21 (no signal to ignition primary circuit), and 12 (MAF--but this was just after I'd been checking it). I have noticed that the engine check light only comes intermittently, and only when when you try to rev the engine while it's missing. (Strangely, the last two ECU mode III checks showed 55 (normal!)

ECU mode I shows green/red both lit, mode II is green only. This indicates the fuel mixture is OK (I think). It definitely seems like an ignition timing problem to me, but damned if I can find the source of it.

Any help would be much appreciated--thanks!
Shaggy


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smj999smj
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Postby smj999smj » Wed Sep 23, 2015 5:46 am

It sounds like you need a new distributor....a fairly common failure on VG-series engines. They tend to start to fail as they get hot until there's no spark. Once they cool off, they'll work again for a little while. It would also explain your ignition system trouble code and the "rattle" might be the shaft bearing failing inside the distributor.

shaggy
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Postby shaggy » Wed Sep 23, 2015 8:11 am

smj999smj wrote:It sounds like you need a new distributor....a fairly common failure on VG-series engines. They tend to start to fail as they get hot until there's no spark. Once they cool off, they'll work again for a little while. It would also explain your ignition system trouble code and the "rattle" might be the shaft bearing failing inside the distributor.
Hi and thanks-- Are you talking about the crank position sensor electronics going out and/or the shaft bearings? I guess I'll take the whole distributor off and check.

cheers
Dave

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smj999smj
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Postby smj999smj » Wed Sep 23, 2015 12:37 pm

Yes, they are both prone to failure, which is why it's usually best to replace the distributor assembly. If it starts running bad to the point where it stops running and you find you have no spark, chances are that's where your problem is.

shaggy
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Postby shaggy » Fri Sep 25, 2015 7:47 am

smj999smj wrote:Yes, they are both prone to failure, which is why it's usually best to replace the distributor assembly. If it starts running bad to the point where it stops running and you find you have no spark, chances are that's where your problem is.
Looks like you were right first time--the top bearing is shot and there's probably enough play in it to drive the sensor crazy.
I've ordered a new bearing and also a complete used/tested OEM distributor.

It's uncanny how it only started to miss after warming up... I wonder if this is the whole story... guess we'll see!

thanks again
Dave

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smj999smj
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Postby smj999smj » Fri Sep 25, 2015 9:45 pm

I would've just gotten a new distributor, but that's me.
Last edited by smj999smj on Tue Jul 16, 2019 9:31 pm, edited 1 time in total.

shaggy
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Postby shaggy » Fri Sep 25, 2015 10:24 pm

smj999smj wrote:I wouldn't just gotten a new distributor, but that's me.
Why on earth? The bearing was the only faulty part! Lord knows what a whole 'new' distributor would cost, if you could even find one. Or did you mean rebuilt? Well, I just rebuilt mine for $8.00 and a couple of of hours' work--and with a great deal of satisfaction 8>)

(I have done this sort of for a living, BTW, but it's hardly rocket science.)

And many thanks for your suggestion--I was a little too focused on 'these darned newfangled computer sensors', when it turned out it was just an old-fashioned mechanical fault.

cheers
Dave

vojta
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Postby vojta » Mon May 27, 2019 10:46 pm

Hi, I'm getting to the same point as shaggy. Cold driving is without any problem, but when it gets warmed up, there are significant misfires. How do you do that cool trick with the bearing swap? I looked for the bearings at rock auto, but it seems to that they have just complete distributor, not just the bearing. Thanks for the tips!

shaggy
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Postby shaggy » Mon May 27, 2019 11:12 pm

It's easy to change (I can't remember all the details any more, probably just needed to remove a circlip and drive the shaft out - it wasn't tight), but if you can't find the bearing, look for a good used distributor off e/b -- or just get the refurbed one.
I've got one for a spare (ordered before I found the bad bearing), but so far the orig. dist. w/ replaced bearing is still going fine.
'Course, your problem might have a different cause, but it's one place I'd look.
Good luck.

vojta
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Postby vojta » Tue May 28, 2019 7:48 am

So far I have replaced distributor cap and rotor (the center connector was oxidized and the plastic around was cracked). It helped a bit, but still noticable hesitation at rpms around 2000, going uphill even worse. I just got back from a 500k trip, so it is drivable and it doesn't stall.. What other things it could be? I was thinking about MAF sensor, maybe cleaning could help?

shaggy
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Postby shaggy » Tue May 28, 2019 8:49 am

Is there play at the top of the dist. shaft? Mine had tons, but with yours you may or may not be able to tell. Bearing might still be bad even if you can't feel any play. Again, not saying for sure it's your problem -- but your symptoms do sound similar to what I had. At this point I'd just go ahead and replace the distributor with a refurb/'new' one. Then at least then you'll know one way or the other.

I was in the same position and was given all the usual suggestions: bad sensors, valves, etc. Replaced plugs, plug leads, cap, O2 sensor, etc etc but nothing changed until I decided to check the dist. more carefully, and found it.
I'm afraid it's a bit of a crapshoot, unless you can systematically track the symptoms. Check or replace things that are easy and cheap first, narrow it down, eventually you'll find it. Sorry I can't offer more help than that.
Good luck.

vojta
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Postby vojta » Tue May 28, 2019 7:03 pm

Thanks for the tips, the distributor is going to be the next thing. Let you know during the week!

vojta
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Postby vojta » Tue Jul 16, 2019 1:33 pm

No play in distributor shaft, so I started with spark plugs, seemed super worn. After replacing that I have put more than 3000 km and works pretty good! Just simple fix :-) thanks guys


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