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

[shaggy]

If ist not a metered item (sensor) then no.

 

With a misfire this bad I'd have thought one sensor or another would have reported a symptom (apart from the detonation sensor, which is really just a vibration indicator). What would you expect a good OBD scanner to indicate, monitoring the misfire in real time?

 

thanks

Dave

Edited September 15, 2015 by shaggy

[BendRed]

95 is obd1 so Im not sure a scanner is available - just the ecu system check under the front passenger seat.

[shaggy]

95 is obd1 so Im not sure a scanner is available - just the ecu system check under the front passenger seat.

 

I only found this one. Does both I &II--comes with a shxtload of connector/adaptors. Looks pretty good to me and gets good reviews:

 

http://www.amazon.com/gp/product/B000KID2ZC/ref=as_li_ss_tl?tag=shopperz_origin2-20&SubscriptionId=AKIAJO7E5OLQ67NVPFZA&ascsubtag=50610786-2-1833947776.1442262557

 

Whaddya think?

 

Dave

[shaggy]

 

I only found this one. Does both I &II--comes with a shxtload of connector/adaptors. Looks pretty good to me and gets good reviews:

 

http://www.amazon.com/gp/product/B000KID2ZC/ref=as_li_ss_tl?tag=shopperz_origin2-20&SubscriptionId=AKIAJO7E5OLQ67NVPFZA&ascsubtag=50610786-2-1833947776.1442262557

 

Whaddya think?

 

Dave

 

I just checked w/ the Innova rep and he says nope it won't work on Nissan OBD1, only Chrysler/GM/Toyota. Too bad.

 

Back to staring at blinking LEDs under the pass. seat 8>/

 

Dave

Edited September 15, 2015 by shaggy

[shaggy]

You need to perform a fuel pressure test and rule out the fuel pump.

 

OK, I've got hold of a fuel pressure gauge... I can't find anything in my useless Haines and Chilton manuals about where to connect it. Can I assume putting it inline between the fuel filter outlet and the injector rail inlet would be correct? If so, with engine running, I get a reading of a big fat Zero--needle didn't move a smidgen! (The gauge works, I checked it on the air compressor.) So either I'm doing it wrong, or...?

 

I'll continue studying up while I wait for an answer--thanks!

 

BTW, another clue: Engine will start cold and drive 3-4 miles without misfiring. But try to park, then start the engine again while it's warm, and forget it--she just refuses to start and farts around with one cylinder almost catching, but not quite, almost like it's flooding (I think I smell gas at that point, but can't say if it's actually starting to flood or not.. 8>/

 

Anyway...back to the fuel pump and pressure regulator check... proper placement of fuel pressure gauge? (I don't think there's a Schrader valve for it on this model(?)

 

thanks guys

Dave

[shaggy]

 

OK, I've got hold of a fuel pressure gauge... I can't find anything in my useless Haines and Chilton manuals about where to connect it. Can I assume putting it inline between the fuel filter outlet and the injector rail inlet would be correct? If so, with engine running, I get a reading of a big fat Zero--needle didn't move a smidgen! (The gauge works, I checked it on the air compressor.) So either I'm doing it wrong, or...?

 

I'll continue studying up while I wait for an answer--thanks!

 

BTW, another clue: Engine will start cold and drive 3-4 miles without misfiring. But try to park, then start the engine again while it's warm, and forget it--she just refuses to start and farts around with one cylinder almost catching, but not quite, almost like it's flooding (I think I smell gas at that point, but can't say if it's actually starting to flood or not.. 8>/

 

Anyway...back to the fuel pump and pressure regulator check... proper placement of fuel pressure gauge? (I don't think there's a Schrader valve for it on this model(?)

 

thanks guys

Dave

 

Unless I'm wrong...the reason the gauge reads zero is because the 'T' adaptor has a Schrader valve in it, but the fitting on the end of the gauge has nothing inside of it to depress the pip of the valve (to open it) when you screw it on. In other words, the fuel pressure can't be monitored with this setup(!) Back to the parts store...

 

Dave

[shaggy]

 

Unless I'm wrong...the reason the gauge reads zero is because the 'T' adaptor has a Schrader valve in it, but the fitting on the end of the gauge has nothing inside of it to depress the pip of the valve (to open it) when you screw it on. In other words, the fuel pressure can't be monitored with this setup(!) Back to the parts store...

 

Dave

 

PS--I can hear the fuel pump run for 6-7 seconds when I turn the key. It sounds healthy and deposits nearly a half-pint of gas into a container every time I've tried it so far, so I'm doubting it's the fuel pump.

 

Any ideas about the cold start and run OK/no-start when warm symptom?

 

I have a new O2 sensor to put in when I get a chance, but the heater coil on the old one has continuity and is getting 12V, and when I disconnect it while the engine is misfiring it continues to misfire.

 

The MAF is also getting juice. I still have a lot more electrical checks to do...

 

Dave

Edited September 16, 2015 by shaggy

[byob]

Pull the rotor off and then the inspection plate that covers the crank sensor. See if there is metal in or around the wheel sensor. When the dist go bad the bearings fail and scatter metal aorund. Check the fuel preesure regulator and make sure the vacum hose is not full or fuel. Your psi should be around 35 psi and go up as you rev. Just some easy things to check

[shaggy]

Pull the rotor off and then the inspection plate that covers the crank sensor. See if there is metal in or around the wheel sensor. When the dist go bad the bearings fail and scatter metal aorund. Check the fuel preesure regulator and make sure the vacum hose is not full or fuel. Your psi should be around 35 psi and go up as you rev. Just some easy things to check

 

Hi--Thanks! I'll check the crank pos. sensor and disc. I've had the hose off the FP regulator to snip the end, and it was dry. Sure hope the reg doesn't need to be replaced way back under there... 8>/

 

Could a bad MAF sensor allow cold start and run, then cause misfiring/no-start when warm? EGR valve/etc should probably be looked at too.

 

Other thing is I'm wondering whether I've blown the CAT--the exhaust system sounds weird somehow, like something might have blown out...

 

Oh yeah... today when I tried to start it warm, it got going but wouldn't rev, like I expected, and when throttled up I got some mean crackling backfires from around the exhaust manifold, like a bad air leak. This doesn't happen in the 'well-behaved' pre-really-bad-misfire mode though. Weird.

 

Thanks again

 

Dave

Edited September 17, 2015 by shaggy

[mechanicalbaron]

I personally think you should be looking at the distributor. To start. I would remove the cap,rotor, and inspection cover. If no metal is found I would remove it and check that it will spin without resistance.

 

Sent from my SM-G920V using Tapatalk

[shaggy]

I personally think you should be looking at the distributor. To start. I would remove the cap,rotor, and inspection cover. If no metal is found I would remove it and check that it will spin without resistance.

 

Sent from my SM-G920V using Tapatalk

 

Hi--Thanks for your suggestion. I will certainly do that next. I replaced the cap and rotor, but wasn't at the time aware of the location of the crankshaft position sensor.

 

cheers

Dave

Edited September 17, 2015 by shaggy

[BendRed]

Hmm ....... maybe a plugged cat!

I have had them come in to the shop with a hard start , then fine for a while then no start /hard drive due to the inners coming apart and partially clogging the exhaust way.

But ..... this is just a (possibility) .

Still need the fuel pressure and spark/timing checked out before moving on.

[shaggy]

Hmm ....... maybe a plugged cat!

I have had them come in to the shop with a hard start , then fine for a while then no start /hard drive due to the inners coming apart and partially clogging the exhaust way.

But ..... this is just a (possibility) .

Still need the fuel pressure and spark/timing checked out before moving on.

 

I hope not 8>/ I've got a good muffler guy, maybe he can give a diagnosis.

 

Yeah I gotta find out what's up with the fuel pressure gauge they gave me. Guess I could just remove the Schrader valve before I hook it up, seeing as the gauge has a pressure release valve and a long drain pipe.

 

I'll get to the bottom of this...

 

thanks

Dave

Edited September 17, 2015 by shaggy

[shaggy]

Hmm ....... maybe a plugged cat!

I have had them come in to the shop with a hard start , then fine for a while then no start /hard drive due to the inners coming apart and partially clogging the exhaust way.

But ..... this is just a (possibility) .

Still need the fuel pressure and spark/timing checked out before moving on.

 

"Still need the fuel pressure and spark/timing checked out before moving on."

 

Well I removed the Schraeder valve from the 'T' piece and connected it inline after the fuel filter. Screwed on the gauge. Turning the ignition key, gauge jumps to around 42psi. On startup (instant misfiring, w/ engine barely warm 2hrs after a 4 mile commute), gauge reads a consistent 34-35psi from idle thru as far as it will rev (at this point not over 2200rpm). At idle (which it does fine), disconnecting vac hose from the pressure regulator, the reading jumps to 44-45psi (vac tube is sucking air).

 

So it's lower than spec, so maybe a weak pump or the screen needs cleaning(?) I don't think the fuel pressure's low enough to be the cause of the trouble...but I could be wrong. Pressure regulator seems to be OK.

 

What do you guys think? Further tests needed, or can I take the gauge back to the shop?

 

Dave

Edited September 17, 2015 by shaggy

[byob]

if the cat is plugged try unplugging the y pipe. Ohm the injectors. Make sure the resistance is no higher than 14.0 ohms

[shaggy]

if the cat is plugged try unplugging the y pipe. Ohm the injectors. Make sure the resistance is no higher than 14.0 ohms

 

What's the Y pipe? 8>|

[BendRed]

The Y pipe is where the 2 exhaust manifolds come together right before the Cat in the form of a "Y" .

[shaggy]

The Y pipe is where the 2 exhaust manifolds come together right before the Cat in the form of a "Y" .

 

That's what it sounded like, wasn't sure --thanks. It's a rust encrusted mess there. I'm replacing the O2 sensor tomorrow so I'll probably get an eyeful of it. 8>|

 

thanks

Dave

[mechanicalbaron]

 

That's what it sounded like, wasn't sure --thanks. It's a rust encrusted mess there. I'm replacing the O2 sensor tomorrow so I'll probably get an eyeful of it. 8>|

 

thanks

Dave

If you're replacing the o2, drive it while you have it out, little easier than disconnecting if it's really rusty.

 

Sent from my SM-G920V using Tapatalk

[shaggy]

If you're replacing the o2, drive it while you have it out, little easier than disconnecting if it's really rusty.

 

Sent from my SM-G920V using Tapatalk

 

Didn't get your message until now, but I only just finished replacing the O2 sensor (Bosch) with a new Borg-Warner one. Bxxtch of a 2 hour job on a gravel driveway, but it's done. I don't necessarily expect that was it, but you never know. Earlier testing showed it had juice and ground, and the heater coil had continuity, but I guess (hope) it still could've been bad. Disconnecting it with engine running/ misfiring didn't change anything, but that mightn't mean much. I'll have my fingers crossed when I start it to get home later. Starting the engine briefly a minute ago didn't tell me much except about the exhaust system--sounds like everything forward of the muffler is clapped out. (CAT?) 8>|

 

Other checks today:

 

Took the dist. cap and rotor off and checked the crank angle sensor disc. No damage, no debris but a film of soot. Removed it and cleaned it. All looks OK... unless the sensor itself is acting up(?)

 

The MAF (engine running, but barely warm) has a good ground, 12V supply, and is putting out a smoothly varying 1 to 5 Volts.

 

The throttle position sensor has good ground and 12V and puts out the specified 0.4 to 4 Volts signal smoothly, from idle thru to full throttle position (engine not running).

 

The EGR system might be a candidate. All I've been able to check on it so far is that the diaphragm is free to move.

 

Will continue checking tomorrow...

 

Thanks for your help, guys.

Dave

[Slartibartfast]

Was the dust in the distributor sort of reddish? I remember reading that red dust in there is a sign of the bushing going out. Given that the angle sensor is optical, the dust could be causing problems. I've also read that a distributor going out will act up more as it warms up.

 

Your fuel pump readings look fine to me. EF&EC 139 says ~34 psi with the regulator hooked up, ~43 unhooked, which is right in with your readings. I think you can rule out the fuel pump.

 

 

[shaggy]

Was the dust in the distributor sort of reddish? I remember reading that red dust in there is a sign of the bushing going out. Given that the angle sensor is optical, the dust could be causing problems. I've also read that a distributor going out will act up more as it warms up.

 

Your fuel pump readings look fine to me. EF&EC 139 says ~34 psi with the regulator hooked up, ~43 unhooked, which is right in with your readings. I think you can rule out the fuel pump.

 

 

 

Hi--No, it wasn't reddish at all, just a very light sooty film, like maybe graphite--but really hardly anything at all; the slots definitely weren't plugged or anything. So, not the disk, or the bearings. But still...maybe the sensor electronics(?)

 

It definitely wasn't the O2 sensor, I can rule that out. Driving home tonight everything was just the same, the miss starting about 4 miles down the road, getting worse as the engine got hotter, and then farting and missing at lower revs, then a sharp backfiring from the exhaust manifold when revved.

 

At least now I can start to rule a bunch of things out.(including the fuel pump--thanks) ...

 

Will look at the EGR valve tomorrow if I can find some info on what to check for...

 

hope you guys have a good weekend 8>]

Dave

[BendRed]

Any back fires at the air box ?

If so then you would have a vac leak and more then likely at the intake manifold .

Just a thought.

[adamzan]

Check the coolant temperature sensor. It's not a clogged cat. You need to test all the sensors and injectors and compare to values in fsm. If it runs fine cold but bad warmed up, it means when the ecu goes to closed or open loop or whatever it is getting bad data. This was the o2 sensor on my rig. Never heard of a Borg Warner o2? These trucks run best with a Bosch or ntk. Was this a direct fit sensor? The universals are @!*% so don't even bother. As a test unplug the o2 cold and try driving. If it still does it plug it in and do the same with the coolant temperature sensor.

 

I'm not sure why people on here recommend throwing fuel pumps and catalytic converters at the truck...this isn't some domestic pos ford explorer.

 

Sent from my SGH-I747M using Tapatalk

[shaggy]

Any back fires at the air box ?

If so then you would have a vac leak and more then likely at the intake manifold .

Just a thought.

 

If you try to rev it sharply it spits and pops around the left side manifold(s)--can't tell if it's exhaust or intake, but it does sound like an air leak. Does not do this when cold, only in closed loop mode.

 

Mine has the EGR valve plus another piece with a vac fitting on top--probably a pressure switch, or thermostat--but I can't find anything that looks like it, or any reference to it in the books. I'll try undoing some of those vac hose with the engine running and see what happens... something seems to be causing a leaning off...

 

thanks

Dave