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

 

 

Edited ...

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

How much have you spent thus far trying to fix this ?

 

Hi BR... Not that much really, maybe $150. Why?

 

I haven't even spent this whole time on it--just spare moments and weekends-- because I've had to work. I'm trying to make the time and money I spend on it count.

 

BUT, right now I can actually afford to throw a couple hundred (parts mentioned in previous post) at it. I would do that in a heartbeat, if I believed that's all it would take.

 

Doubts about the catalytic converters and bad exhaust manifold are what's holding me back. As much as I love this vehicle, I can't see putting $1000 or more into it.

 

cheers

Dave

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

Sorry I meant reground. Make sure that the actual ground lead is double grounded to a good ground position.

 

What's weird is the runs OK the bad when warming up/hot.

 

This makes me believe it's a coolant temp sensor, cylinder head temp sensor, or oxygen sensor or maybe egr. All other sensors are just reading a variation or variables. Nothing temp related.

 

Good luck but I would start with the 3 major. Fuel / compression / spark. You know you have good fuel pressure and spark, well check the timing to make sure its not doing anything wanky. Then verify fuel pressure when misfire studder and any issues. This means an inline gauge you can see while driving.

 

Does this happen only under load or also under idle no load conditions?

 

Will check grounds again, but I have a feeling it's not gonna be something that simple.

 

The coolant temp. sensor's resistace readings are OK, and I replaced the O2 sensor...

 

There was a period where she wouldn't start hot, and I was getting the no spark fault code... other times it seems like intermittent spark, or the timing going nuts.

 

Fuel is good as far as I can tell. Compression... I'm scared to check(!) --but it's been running fine. Gotta be something affecting the timing, or killing the spark...

 

I have tracked down an ECU (used), a CPS (new), and a MAF sensor (used), $150 worth. It might be worth the gamble...

 

Dave

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

I highly doubt the knock \ detonation sensor is your problem. If you look on eBay you can find inexpensive replacements that work just fine.

 

Have you checked your aac valve? This was bad on my 92 and was causing problems for me. If you can pull the harness connector at the front passenger side of the engine to test its easier. It should be 10 ohms.

 

Also rebound your maf. This is almost mandatory with any of these vehicles.

 

Have you confirmed your timing with a timing light?

 

Hi and thanks for replying.

 

I thought it probably wasn't the knock/detonation sensor, I just wanted to make sure as I've read different opinions.

 

AAC? Will look it up and put it on the list.

 

Not sure what you mean by 'rebound' the MAF(?) I've cleaned it and checked it out electrically, with engine running--the voltage increase was smooth and within spec. But I didn't check it hot, just warm, so I'm not 100% sure.

 

No I haven't checked the timing yet. With the engine starting and running OK cold, I've been looking elsewhere. But yeah, it it could be going haywire when something heats up. I need to get another timing light (someone stole it awhile back). I wished I had it when the misfire started happening.

 

Thanks for your suggestions!

 

cheers

Dave

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

PS--

 

Given the symptoms (starts and runs cold, sputters and dies after getting hot, no spark/no start when hot)...

 

Since I've replaced: plugs, plug wires, dist. cap and rotor, fuel filter, air filter, O2 sensor...

 

Checked/eliminated: Fuel pump, coolant temp sensor, CPS (disk)...

 

What do you think are the chances it's:

 

Crankshaft position sensor (electronics block)?

 

HT power transistor?

 

MAF?

 

One or more fuel injectors?

 

Bad CAT?

 

EGR/BPT valves?

 

ECU?

 

??

 

thanks

Dave

 

Another couple questions:

 

If the detonation/knock sensor is bad, could it be giving the ECU enough wrong data to be contributing to the problem (say retarding the ignition timing)?

 

I may have mentioned this, but along with the misfiring, there's some wheezing and flapping and undue noise around the left side manifolds (both intake and exhaust), and possibly the CATs and 'y' junction (which looks like a heap of rust, BTW). Thinking this could be an additional problem, on top of the no-spark when hot symptom.

 

I'm tempted to buy some used ignition parts (CPS, power transistor, and ECU)to throw at this. I could do it for under $150 and it might solve the problem. (Yeah, I know, used parts--but I can't afford 3x for new ones.)

 

Any more ideas?

 

thanks for your time guys

Dave

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

PS--

 

Given the symptoms (starts and runs cold, sputters and dies after getting hot, no spark/no start when hot)...

 

Since I've replaced: plugs, plug wires, dist. cap and rotor, fuel filter, air filter, O2 sensor...

 

Checked/eliminated: Fuel pump, coolant temp sensor, CPS (disk)...

 

What do you think are the chances it's:

 

Crankshaft position sensor (electronics block)?

 

HT power transistor?

 

MAF?

 

One or more fuel injectors?

 

Bad CAT?

 

EGR/BPT valves?

 

ECU?

 

??

 

thanks

Dave

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

 

Hi -- I understand, and I appreciate your help anyway.

 

Maybe it'll turn out to be something simple--that's often the case, but you dare not hope too much. Still...

 

cheers

Dave

 

Well guys, me and the Pathfinder had a horrible weekend. It was hot hot hot, and she'd barely do three miles from a cold start without starting to stutter and shut down, at which point nothing will get her going again short of sitting overnight wherever she happens to stall out. No more driving anywhere, unless it's to a garage or to the wrecking yard 8>/

 

Without throwing a few hundred dollars worth of parts at it that it maybe doesn't need or justify, I'm near the end of the road here.

 

Any ideas?

 

thanks!

 

Dave

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

Wish I could be more helpful, a lot easier when you have it in front of you and can actually see what is happening.

There are a lot of good feedback on this post from the other members.

Best of luck.

 

 

Sent from my SM-G920V using Tapatalk

 

Hi -- I understand, and I appreciate your help anyway.

 

Maybe it'll turn out to be something simple--that's often the case, but you dare not hope too much. Still...

 

cheers

Dave

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

Esm=electronic service manual. Also called assist.

I could also have overlooked K ohm spec. Not at work right now to double check but I think I did.

As I understand it you can download the manual from NPORA. and verify that spec.

Did you remove the distributor and check that the shaft turns freely? Quick and simple test and you need to eliminate that as a possibility. I've seen a lot of problems with the shaft bearings.

And one last though, pull off the cap and have a friend crank it over to make sure the rotor is turning ( referring to no spark).

 

 

Sent from my SM-G920V using Tapatalk

 

Hi-- Yes, I removed the distributor cap yesterday to check the CPS disk. Everything in there looks good (the soot I mentioned was barely visible and nothing more than I'd expect), and I know the shaft and rotor turn because I cranked it a few times to get the screw to line up. I'll check it again, although I doubt anything's changed. I'm tempted to buy a power transistor unit, but it could as easily be the CPS block... or the ECU... or(?)

I've taken apart and cleaned all the +ve terminal blocks around the battery. I guess I'll start double-checking all the power and grounds again, including the transistor...

 

thanks!

Dave

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

I work at the dealer, looked up in the esm while I was at work today.

If you bought one might as well put it in and check if it's helped.

 

Sent from my SM-G920V using Tapatalk

 

Well, thanks... esm (?) But I think it was wrong specs for my vehicle. The new one and my original both track temperature the same as far as I can tell. Anyway, it was good to check it.

 

The big problem now looks like no spark at all anymore. Maybe something's been on the way out all this time 8>/

 

Will be looking for electrical test procedures on the power transistor, and crank position sensor electronics. After that, I dunno...

 

Dave

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

The sensor with the single pin is for the temp gauge on the gauge cluster.

 

Sent from my SM-G920V using Tapatalk

 

Yes, I figured that out thanks.

 

BTW, where did you get the resistance figures for the 2-terminal one from? I checked mine against a new one at the parts store, and they're both in the range of 1.5k Ohms at room temperature. Sticking them in near boiling water, the resistance goes down to 700 Ohms or so, but nothing like as low as your specs. I bought the new one just to test mine properly, it was only $20.

 

I'm on to checking that transistor now, and looking for spark... wonder if it's back now the engine's cooled off... 8>/

 

Dave

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

The two terminal sensor is or the ecm, if it's open it is bad. Double check to be sure. The Esm states that backfire through exhaust can be caused by a failed coolant temp sensor.

Possibly you have two separate problems. Follow the esm and check the power transistor.

If you know anyone else that's close or have a junkyard close you can simply swap it to check.

 

Sent from my SM-G920V using Tapatalk

 

Sorry, are you saying the unit that's closer to the engine block (with two wires and the yellow block connector) is the coolant temp. sensor? That figures. It's just that I saw a pic of the single-terminal one somewhere labeled that. What is that one, then?

 

If it's open, I guess that could cause the problem I'm having (misbehaving only when warmed up)?

 

I'll check the price of a new one at the parts store, maybe it's not too much...

 

Can't get to a junkyard that easily right now. I should be able to do a stand-alone check on the transistor first....

 

Thanks

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

Check the coolant temp sensor, resistance should be 2.1-2.9 ohms at 68 degrees Fahrenheit, .68-1.0 at 122F and .30-.33 at 176F. Check it with the vehicle hot and failing.

Forget the egr system. That is the least likely to cause what you say is happening.

Did you remove the distributor and check that the shaft turns freely? Any dust or soot should not make it inside, should be sealed.

Forget the knock sensor code, most likely is being set due to the problem your having.

Probably should look closer into the ignition code. Check the power transistor. Follow diagnosis procedure 27 in the Esmond page ec-90

 

Sent from my SM-G920V using Tapatalk

 

If you're talking about the front-most unit (with the single spade connector) of the two devices screwed into in the coolant inlet manifold, it's resistance, from spade terminal to ground (engine warm) is way over your spec-- it's a bit over 155 Ohms--no kidding(!) --and I do I know my multimeter and Ohms Law.) 8>)

(The second unit with two terminals I think is a switch, and reads open circuit as it probably oughta.)

 

In kind of a new development, the engine will not even fire when warm (maybe not even cold now, either). And the ECU gives a consistent code 21 (no signal to coil primary) --so basically, zero spark as of now. (I switched to a spare ignition coil to no effect.)

 

So, I'm thinking 'bad power transistor'(?) Damn thing is 60-70 bucks for a new Bosch, though, so I wanna be sure. And I hope it isn't the Crank Pos. Indicator electronics, 'cause that's even more $$$.

 

Between no spark at all, and bad coolant readings, maybe we got something...?

 

BTW, I'm reluctant to heat up the engine because I know it won't start until it cools again for hours, but that may all be a moot point now, as it won't even fire (mis or not)... 8>/

 

thanks again

Dave

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

 

Coolant temp. sensor... ok, I will try and check it.

 

Should I try running it with the coolant temp. sensor disconnected from the get-go and see what happens? So far nothing seems to have changed the basic symptoms, they just get more severe as the temp. goes beyond a certain point--after the sensor/feedback system goes closed-loop (by the sound of it).

 

Hope it's not the O2 sensor. It was a direct fit 3-wire job, even the same wire color coding. (They stated the brand on ebay, but maybe they got it mixed up with a brake or clutch part, wouldn't be surprised LOL!) I hope it's OK-- that was a lot of damn work to put in; I've still got a sore neck(!)

 

What about the EGR system?

 

 

thanks

Dave

 

If it's of any use, the second picture in post #10 on this page:

 

http://www.nissanpathfinders.net/forum/topic/36294-engine-pictures-for-information-and-comparison/

 

... shows exactly the setup I have in regard to the EGR/BPT valve system (i.e. CA -compliant vehicle).

 

I just checked mode III ECU codes and I now have a 12 (air flow meter circuit), a 21 (ignition signal missing primary coil), and the usual 34 (detonation sensor). First time I've seen a 12, but it might be to do with the electrical checks I just made.

 

Thanks for any further thoughts...

 

Dave

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

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

 

Coolant temp. sensor... ok, I will try and check it.

 

Should I try running it with the coolant temp. sensor disconnected from the get-go and see what happens? So far nothing seems to have changed the basic symptoms, they just get more severe as the temp. goes beyond a certain point--after the sensor/feedback system goes closed-loop (by the sound of it).

 

Hope it's not the O2 sensor. It was a direct fit 3-wire job, even the same wire color coding. (They stated the brand on ebay, but maybe they got it mixed up with a brake or clutch part, wouldn't be surprised LOL!) I hope it's OK-- that was a lot of damn work to put in; I've still got a sore neck(!)

 

What about the EGR system?

 

 

thanks

Dave

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

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

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

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

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

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

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

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

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

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>|

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

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

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

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

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

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

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

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

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

 

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