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'95 Pathfinder misfiring over 2500 rpm--but only when warmed up


shaggy
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You might try running it with the MAF unplugged. The computer should go to to stored values then. If the MAF is reading horrendously out from where it should be, the stored values would be an improvement. If not, I'd guess it's not the MAF. If pulling it does make it run better, it could be the MAF, or it could be going back to open loop and ignoring an erroneous input from another sensor.

 

I've only read about one ECU failure by natural causes (not counting submarine attempts as natural) and IIRC that one was an instant fatality.

 

My money's still on the dizzy.

 

Hi--Only time I tried unplugging the MAF w/ the engine running, it just died instantly. Figured it wasn't supposed to be able to run with it unplugged. If that's not the case I'll have another look. (I only got a MAF code once, after I'd had it unhooked.)

 

I agree, the distributor is a good possibility still. Or the transistor module..

 

I'll take the distributor off over the weekend and check the crank pos. sensor. But I think I'll try swapping the transistor module and see what happens. I can do that at work today...

 

thanks

Dave

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shoot man , $150 would have gotten you professional diagnostics done and then you would know exactly what needs to be fixed .... just saying.

 

 

I don't regret any part I've replaced so far, as long as the truck goes again. Dist. cap center contact was shot, plugs were old, fuel filter was dirty, etc... all stuff I should've done anyway.

 

I have no clue where I would take it to get a 'professional diagnostics' done. Most garages around here I wouldn't trust with a lawnmower! The one mechanic I knew to trust died just a couple months ago (RIP, Glen) 8>/

 

I was a mechanic before, and despite computers, I aim to fix this. And I will, with you guys' help(!) Thanks.

 

Dave

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I don't regret any part I've replaced so far, as long as the truck goes again. Dist. cap center contact was shot, plugs were old, fuel filter was dirty, etc... all stuff I should've done anyway.

 

I have no clue where I would take it to get a 'professional diagnostics' done. Most garages around here I wouldn't trust with a lawnmower! The one mechanic I knew to trust died just a couple months ago (RIP, Glen) 8>/

 

I was a mechanic before, and despite computers, I aim to fix this. And I will, with you guys' help(!) Thanks.

 

Dave

 

Well I took a gamble on a new power transistor unit. Once the engine warmed up, the same misfire began happening again--first faintly at 4000-4500 rpm, then getting more pronounced, and at lower rpms as it's been doing. In a word, no change.

 

One more thing eliminated, at least...

 

Dave

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Well I took a gamble on a new power transistor unit. Once the engine warmed up, the same misfire began happening again--first faintly at 4000-4500 rpm, then getting more pronounced, and at lower rpms as it's been doing. In a word, no change.

 

One more thing eliminated, at least...

 

Dave

 

Update: Checked ECU codes after the last misfire event, and it said 'normal' = 55 (!)

 

Then a couple of hours later (engine still quite warm), she would not start, no way. Code 21 again - 'no signal to ignition primary circuit'.

 

I'll take the distributor off next, I guess.

 

 

She started and ran fine earlier, as usual (engine stone cold) ... 8>|

 

Dave

Edited by shaggy
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I don't regret any part I've replaced so far, as long as the truck goes again. Dist. cap center contact was shot, plugs were old, fuel filter was dirty, etc... all stuff I should've done anyway.

 

I have no clue where I would take it to get a 'professional diagnostics' done. Most garages around here I wouldn't trust with a lawnmower! The one mechanic I knew to trust died just a couple months ago (RIP, Glen) 8>/

 

I was a mechanic before, and despite computers, I aim to fix this. And I will, with you guys' help(!) Thanks.

 

Dave

 

Well then its a good thing thus far . Nice

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Well then its a good thing thus far . Nice

 

Had some time this afternoon, so I took out the distributor. The bearings are intact with no undue play in any direction, but feel rough and worn. Turn shaft some more and I'm getting binding, a bit like I'm winding up a rubber band (I'm thinking a ruined seal is wrapped around the shaft?)

 

Leaving dist. connected electrically, I switched on the ignition and tried slowly turning the shaft.

 

There's a sequential clicking (I guess injector actuators), but also a very random louder click of a relay coil on and off... WTF?

 

Turning some more, and I feel the slight binding on the shaft. Wonder if it's the opto sensor rubbing, but there's no marks on the CRS disk. So, what's binding? Dist. is on my bench as we speak, about to come apart...

 

More news in a bit...

 

Dave

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Had some time this afternoon, so I took out the distributor. The bearings are intact with no undue play in any direction, but feel rough and worn. Turn shaft some more and I'm getting binding, a bit like I'm winding up a rubber band (I'm thinking a ruined seal is wrapped around the shaft?)

 

Leaving dist. connected electrically, I switched on the ignition and tried slowly turning the shaft.

 

There's a sequential clicking (I guess injector actuators), but also a very random louder click of a relay coil on and off... WTF?

 

Turning some more, and I feel the slight binding on the shaft. Wonder if it's the opto sensor rubbing, but there's no marks on the CRS disk. So, what's binding? Dist. is on my bench as we speak, about to come apart...

 

More news in a bit...

 

Dave

 

OK, it looks like the needle rollers are shot, that's what was binding, and the vertical play from wear and damage was probably enough to allow the timing disk to rub or make contact and screw the timing up (I'm guessing).

 

I've located a used replacement distributor w/ the same part numbers as this one. I probably should look for a rebuilt one, but it'd be 4x the cost... and who to trust? Any feedback on that?

 

Dave

 

.

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OK, it looks like the needle rollers are shot, that's what was binding, and the vertical play from wear and damage was probably enough to allow the timing disk to rub or make contact and screw the timing up (I'm guessing).

 

I've located a used replacement distributor w/ the same part numbers as this one. I probably should look for a rebuilt one, but it'd be 4x the cost... and who to trust? Any feedback on that?

 

Dave

 

.

 

No needle rollers, just a bushing in the bottom and a ball bearing at the top. The BB is stuffed. Looks like rebuilt distributors start at $150, which probably isn't bad since I assume it includes a new sensor...

 

PS--I still don't know if I've found the source of the problem, or just one more worn out part(!) 8>]

 

Dave

Edited by shaggy
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No needle rollers, just a bushing in the bottom and a ball bearing at the top. The BB is stuffed. Looks like rebuilt distributors start at $150, which probably isn't bad since I assume it includes a new sensor...

 

PS--I still don't know if I've found the source of the problem, or just one more worn out part(!) 8>]

 

Dave

Ummmmmm, should of checked that thing a long time ago. That optical sensor tell the ecm when to fire (ground) the injectors and works with the coil and transistor. Which is why I kept asking if you pulled it out and checked that the shaft spins freely without resistance. I would probably put a used one in if it checked out ok and was really cheap. It looks like you finally isolated you main issue and soon will be able to enjoy your pathfinder.

 

Sent from my SM-G920V using Tapatalk

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Ummmmmm, should of checked that thing a long time ago. That optical sensor tell the ecm when to fire (ground) the injectors and works with the coil and transistor. Which is why I kept asking if you pulled it out and checked that the shaft spins freely without resistance. I would probably put a used one in if it checked out ok and was really cheap. It looks like you finally isolated you main issue and soon will be able to enjoy your pathfinder.

 

Sent from my SM-G920V using Tapatalk

 

Yeah, maybe I should've torn it apart sooner. I sure hope that's it, but I wonder what else in this old gal needs replacing(?) I'll sure be glad to get her going again though 8>]

 

 

thanks

Dave

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Yeah, maybe I should've torn it apart sooner. I sure hope that's it, but I wonder what else in this old gal needs replacing(?) I'll sure be glad to get her going again though 8>]

 

 

thanks

Dave

With my pathfinder I've put a good amount of money into it but with where I work and what I do it's still a lot cheaper than a car payment and much more rewarding. Realistically though I'm in the same boat as everyone else and tend to overthink problems with my own vehicle because it's out of my pocket.

And again it can be extremely difficult to help with problems when you cannot see, listen, and feel what is going on.

Hope that the distributor is the last thing you have to replace and you can enjoy the pathfinder.

 

Sent from my SM-G920V using Tapatalk

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With my pathfinder I've put a good amount of money into it but with where I work and what I do it's still a lot cheaper than a car payment and much more rewarding. Realistically though I'm in the same boat as everyone else and tend to overthink problems with my own vehicle because it's out of my pocket.

And again it can be extremely difficult to help with problems when you cannot see, listen, and feel what is going on.

Hope that the distributor is the last thing you have to replace and you can enjoy the pathfinder.

 

Sent from my SM-G920V using Tapatalk

 

Yeah, I know what you mean. Soon as I got that distributor apart I ordered a new 10x30x9mm sealed bearing(!) An easy fix, but of course the sensor might still be bad. Anyway, I got a line on a complete pulled distributor for ~$50. With old stuff you can never have too many spares, right?

 

thanks again

Dave

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oh man ...... light at the end of the tunnel :aok:

 

Looks like it 8>)

 

If I can find a bearing locally I'll have this baby up and running tonight... (fingers crossed)

 

Dave

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Christ just go to the JY and grab a distributor or buy a new/rebuilt one. Don't piss around with changing the bearings the sensor will likely already be damaged. Just went through this on my Xterra. Except I didn't change every other part under the hood tracking it

Edited by adamzan
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Christ just go to the JY and grab a distributor or buy a new/rebuilt one. Don't piss around with changing the bearings the sensor will likely already be damaged. Just went through this on my Xterra. Except I didn't change every other part under the hood tracking it

 

Im 100% with adamzan!

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Christ just go to the JY and grab a distributor or buy a new/rebuilt one. Don't piss around with changing the bearings the sensor will likely already be damaged. Just went through this on my Xterra. Except I didn't change every other part under the hood tracking it

 

Oh sorry, I thought I mentioned--I got a pulled one on the way that I got for $50. Of course the bearing could be shot in it too, and will certainly have 150k or more on it. I wouldn't put it in without checking, would you?

 

While I'm waiting for that to arrive (next week?) I'll have a brand new bearing in this one today and ready to install ( assuming the sensor is OK). I don't see that as a problem.

 

BTW, most of the parts I replaced badly needed replacing.

 

Thanks for your generous advice 8>)

 

Dave

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I just don't like seeing people throwing parts at a car to fix it. The FSM has all of the info, there is a link in the garage section for it.

 

http://www.nicoclub.com/FSM/Pathfinder/

 

A week to get a used dizzy? Is there not a local place that you can go pull one yourself?

 

I dunno what you mean by 'throwing parts', that's exactly what I've avoided doing. So far everything I checked was old or shot. I bought and returned two new parts after checking them against the old ones (one of them on the suggestion of a fellow NPORA member).

 

Ebay parts are cheap and delivered to your doorstep in a few days (though sometimes not by the weekend, unfortunately). My local wrecker has no Pathy ignition parts, and I haven't got a spare half day to go on a wild goose chase. Meanwhile I'm working and making $$$... and asking questions to help track down the problem.

 

Gotta get back to house-painting now...

 

Dave

Edited by shaggy
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Got itchy fingers, so I took a long lunch break and went and got the new bearing (NSK Japan, identical to the OEM one). Had the distributor reassembled and back in in under an hour. She starts and runs really clean, so I've got no doubt the sensor is good. I'll go for a longer test drive tonight, but I'm pretty sure it's OK.

 

Guess now I'll have a spare distributor on the shelf, just in case 8>]

 

Will check back later.

 

Thanks to everyone for your suggestions and help!

 

Dave

Edited by shaggy
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Interesting. I guess if the shaft was running around in a flogged bearing, the optical slits could've just been misaligned with the sensor or something.

 

Yep, that was exactly it. What gets me is that it would run OK cold 8>|

I was so fixated on them newfangled sensors 'n stuff, I overlooked a simple mechanical fix.

When I finally pulled the dizzy and turned the shaft by hand it was pretty obvious.

 

Anyway, runs like a champ now, and got a lot of badly-needed TLC besides. And I learned a thing or two.

I performed a celebratory vacuuming out last night, then I drove her home and cracked open a bottle of Asahi 8>]

 

I will keep you all updated.

 

Thanks again guys for your help. Have a great weekend!

 

Dave

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