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Random misfire Help!


BrianD
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My 98 pathfinder started missing occasionally when on the highway.

It misses more when U have your foot into it under load but runs perfectly in town at slow speed.

The CEL was not on and no codes. We cudn't duplicate the prolm in the parking lot in drive at 2200 rpm with my foot on the brakes.

I mentioned that I'd changed plugs..except #6 ( it got dark last year so I nvr got it finished) so I finally changed that one. No change.

 

Then changed the cap, rotor and new NGK plug wires(It's got 320,000 km so it was time anyway)..no change BUT now the CEL is on which shows the crank sensor.

I cud NOT get my arm/ hand up in there while in my driveway. Took it back to my mechanic with new $75 sensor in hand.

 

He found that the wires were pulled out off the sensor plug and repaired them. ..how that wud happen? I have no idea cause it's waaay up there. So I nvr installed the crank sensor seeing that was the cause.

 

Drove it today and it's still not fixed. No CEL either. I'll check for codes again IF the CEL comes back on.

It seems like the ignition is breaking down when it misses - when I let off the gas a bit, it goes a away for a while? DUH?!

Cud it be a fuel prolm? Where do I look? Where's the solution?

 

Just added some BG44K and a full tank of gas. Gonna see if it's a sticky injector.

 

Has anyone ever changed a crank sensor on a vg33 and if so, how do U get at it?

I'm afraid if I break it off while removing it I'll have to pull the transmission!

He says they don't always want to co-operate when they are that old. Don't think I need to change it now anyways.

 

Any suggestions on a solution will be appreciated.

I haven't got the bill yet but I'm sure it won't be cheap cause he had to comb the wreckers for similar plugs to find one that wud work.

 

PS - I did change a leaky fuel filter about a month ago but it's was running just fine after that.

Anyone have a similar prolm? Help pls.

 

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I would probably start by looking at misfire count and see if it's coming from 1 or more cylinders. If it's one cylinder I would investigate for either a low compression in that cylinder or faulty injector.

 

If the misfire counts shows that it is all around, then I would look for a vacuum leak after the maf or the distributor cap (even if it has been changed)... Your short term fuel trim will also speak to you.. At that point, you would definitely need an obd2 tool so that you can see what is going on.. or else, you'll just play the replace part game....

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I would probably start by looking at misfire count and see if it's coming from 1 or more cylinders. If it's one cylinder I would investigate for either a low compression in that cylinder or faulty injector.

 

If the misfire counts shows that it is all around, then I would look for a vacuum leak after the maf or the distributor cap (even if it has been changed)... Your short term fuel trim will also speak to you.. At that point, you would definitely need an obd2 tool so that you can see what is going on.. or else, you'll just play the replace part game....

Sorry for being a noob with this ...but How do I look for a misfire count?

A friend mentioned a vacuum leak - wud that be just a visual inspection or is there more I can do?

Again..Sorry man..Noob! How do I ..do the fuel trim...uh thing? I've Nvr heard of it.

This misfire prolm comes and goes and never when it's standing still.

& Yes - now am trying to Avoid to playing the parts replacement game. Thank You. I appreciate your help.

I also sprayed every connector that I cud find with WD 40 too..no change.

Shud I take each connector apart? - I've got this spray stuff called Termin 8R corrosion protection that is pink and bubbles on contact and it werx it's way into the smallest places. A waste of time?

Thanx again. Cheers

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misfire count can be seen with an obd2 scanner.. You will be able to see this real time. A vacuum leak is basically a hole in the air path after the mass air flow or around the air intake gasket etc... A visual inspection can be sometime hard to do if it is a small leak.. The best way I feel is using a smoke machine... you can build yourself one for small amount of $.. check youtube on that (diy smoke machine). The fuel trim (short and long) are what the computer is trying to do in order to compensate either for a lean or rich condition. Again this is monitored using a obd2 scanner...

 

If you do not have (or have access) to an obd2 scanner, you can still test a few things but you will need to be able to duplicate the issue while you start troubleshooting.. (like unplugging sparkplug wire and listening if the engine changes sounds or not... etc... But I would try to get a scanner first...

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Thanx man - I was thinking of getting one of these.. BAFX Products 34t5 Bluetooth OBDII Scan Tool

I'll take my laptop out and see what's happening...I hope to use it while on the highway - yer thots?

 

https://www.amazon.com/BAFX-Products-34t5-Bluetooth-Android/dp/B005NLQAHS/ref=pd_lpo_263_bs_tr_t_2?_encoding=UTF8&psc=1&refRID=EMB3B9G3G2H5VJZ65ZTE

 

It states it werx btr than the cheaper ones and it's only $25!

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It's 25$ for the hardware but then you have to pay for the app... So I guess you need to make sure that you get an app that can read misfire count with this hardware.... I personally use the autel md802 and I have no experience with these bafx products... sorry

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Thanx - I found a guy who will let me borrow his scanner. I thot my laptop has Bluetooth but no & I don't have a super phone or android.. anything.

Sooooo..having nvr used a scanner before I don't know what I shud do with it..besides plugging it in and reading the screen. I've seen my mechanic scroll thru different screens on his. I guess I'll just do the same until something pops out at me? Cheers

 

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UPDATE - PROBLEM SOLVED! - It dawned on this morning that my driver's door interior lights stop working about 3 weeks ago when this prolm started. The on/off interior light switch is located at the bottom right of the door frame. When I'd open the door there was a click coming from a DVD player that was installed when I bought the truck. I dropped it from the ceiling and in a mess of wires was this little black box - I lukd it up and it's a relay that draws between 20- 30 amps.

http://www.texasindustrialelectric.com/relays_0332209150.asp

I took it out of the wiring harness and drove it up the highway with the wires hanging from the ceiling. Voila! No mis-fire!

Not once did I ever use the the damn thing anyway.

Thanx for all your help.

Cheers Brian

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IT'S BACK! I took it out yesterday and it was running great. Got on the highway and bit by bit the misfire returned. MF!!

Cud it possibly be the alternator not producing enuff juice when under load for long periods?

I'm now stumped as to what to look for - I've already checked just about everything I can think of.

I might try taking out the plugs one at a time and look there. I dunno.

So why why why? did it go away after removing the relay switch? Is that sum sorta clue as to what's going on?

Shud I look again at the interior driver door light switch? What the hell?

Any suggestions?

Thanx Brian

 

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a missfire is either electrical, fuel or air related. Mine turned out to be fuel (bad injector) I'd go buy a OBD2 scanner at princes auto you can get them for about 50 bucks or less. it will help you narrow down the problem. being able to see fuel trim levels in real time would be helpful. read this it. http://repairpal.com/OBD-II-Code-P0305

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  • 1 month later...

Sooo...I've been driving my Pathy for a month waiting for something to fail or the CEL light to come on but it has not...and the misfire has been getting worse. Today I stopped at a red light and it quit dead. It started right back up so I took it to my mechanic right away who hooked up his scanner and still no codes...but this time when I opened the hood we heard a crunching sound that wud come and go. It's coming from the distributor! So I HOPE I found the prolm.

No time to werk on it. I found some used ones - $100 - $125 - $160 - new for $250 and a reman from Nissan at $677.44 + taxes.

Your thots on which one to buy? Any advice pls and thanx.

Cheers Brian

 

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I had the same problem with my 99.5. The problem ended up being the bearing on the distributor was falling apart. It was making a growling sound. I took the distributor out and pressed on a new bearing. Problem solved.

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Thanx Dislaugh - hahaha! Luv that name. so this had nothing to do with a misfire tho - correct? ..or did it? U changed it because of a bad bearing only right? I saw a video ( which I can't find now) where the electronics inside the distributor went bad because of excessive heat. Wud a bearing cause a misfire because it's not running true?

and where did U find a bearing for this?

Cheers

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I took what was left of the bearing to a bearing shop and they measured it and got me a new one. I think you might be able to get one at an auto parts store.

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I hope this will finally be the answer to this yes...PITA prolm. Is it worth checking on a distributor machine? Thanx

 

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I didn't have mine checked. It was still working, but not sure how much longer. The bearing was in bad shape. If you have the means to press the old bearing off and then a new one on, I think the parts less than $15.

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