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10 hours ago, Mr_Reverse said:

I was looking at the emission numbers you have and sorry, but CA does things much different. I don't know what GP means. I figure the meas is what was measured and Max is Maximum, though the numbers there seem low. If I am reading it right, the O2 was at 0 and CO2 was 12.7% with elevated HC, CO, and I assume NOx. Those are indicating a rich condition, not enough air to completely burn the fuel. It is likely your MAF giving high readings from everything else I read in your posts. Your work on the connector probably fixed it. A gentle cleaning of the sensor and screen might help too. 

With the O2 sensors, they all use the same bung, and 99% use the same 22mm(7/8") wrench/socket. They also tend to look alike as well. It is inside where they are different. I don't remember off hand, is it a 3 wire sensor? If so, running a ground to the exhaust might help as well, since the sensor is grounded by the pipe. Originally, there was ground straps on both manifolds and a couple of other points on the pipe. Those tend to break over time. 

 

Here we do the sniffer test quite differently. It is done unloaded, no Dyno. First stage is 30 seconds at 2500 rpm(2250-2750) followed by 30 seconds at idle (600-1100 rpm). For autos and light trucks GVRW less than 8000 lbs in the 80s and 90s maximum HC is 210 ppm, CO is 1.2%, and NOx is not measured.  Just for the record, it is counter intuitive, but the emissions tend to be higher when the engine is unloaded than when under load. 

 

 

Yeah, sorry I could not attach the full smog check.  Its a little more clear than that snippet I cut off to meet size of uploadable file restrictions.

GP means Gross Polluter.  Above this level CA gives you some rebate for repairs and many years ago gave $500 to scrap the car.  I did that with a 1981 VW Scirocco I had since new.  The odometer stopped working but I put over 500,000 miles on it.  Original engine, clutch and transmission!!

 

Yes, meas is measured, O2 zero, CO2 12.7%  HC was high, above Max but below Gross polluter, CO was above GP, NO or Nox above Max but below GP.   Results were Gross Polluter because of CO

 

Yes, my O2 sensor is 3 wire.  Rock Auto seems fairly good at accurately matching parts to the vehicle, plus it seems to be working well now.  Great idea about new grounds to the exhaust.  I'll do that.  I see two straps at least to a manifold heat shields.  They both are intact, but I'll bet 10c that the bolt will shear if I try to loosen it - much rust.  I'll make/drill new attachment points.

 

Thanks again Mr R.  Much appreciated.

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Yep, the screws will snap if you try to turn them. Easy way to run a ground straps near the O2 sensor is to weld a tab that you can bolt a ground strap to onto the pipe. Dealing with exhaust is always a pain due to the rust. At least you don't have as much rust as those of us who are in climates that see salt slurry on the roads several months per year. Utah salts the roads, but somehow is not a salt state according to Nissan. 

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Ha!  No salt slurry in CA, but the salt air is present 24/7.  Everything gets corroded  ?

 

So far I hard wired an addition ground to terminal B of the MAFS connector, and it didn't change anything.  I fly jets for a living and I'm beginning to share the frustrations of the mechanics we report problems to and who do what seems like everything possible and its still not fixed.  Thanks for the tab idea.  I don't have a welder so I'll look for a tab already in place, or a bracket or something and clean it up well before adding the ground strap.

 

Best regards

 

john

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The nice thing about working on cars is that you don't generally plummet twenty thousand feet if something goes wrong. :lol:

The plug by the hood release is OBD1. It sounds like Nissan had an adapter for their Consult system (or some version of it, anyway) to make it work with that plug. They also had a more primitive scanner that could plug into that port, which just had two lights and a button, and works just like the lights on the ECM. (The advantage is that it's not under the seat.) Some of the guys on Infamous worked out how to rig one up and I used their notes to build my own. It only used a few of the available connections. Presumably the Consult adapter (or aftermarket equivalent) could access more information from those other pins. Whether that info would be useful in this case, I don't know. But yeah, I'd be shocked if an ECM designed in the '80s to communicate via blinking lights had some kind of hidden wireless capability, or if someone put the effort into making a bluetooth dongle for an increasingly obscure OBD1 system.

 

I took the fender off to access the resonator on mine. The screen I used was a bowl-shaped stamped metal piece meant to hold a foam air filter element for a carburetor (similar to this). I used it mostly because I had one handy. Not a bad idea to clean out in there, but I'd be surprised if something upstream of the MAF (short of a rat's nest blocking airflow) was causing mixture issues. At this point I'd be moving on to the leakdown test.

One other long shot. Have you checked the ignition timing since you put it back together?

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Its got to be a pretty serious problem to plummet to earth - like the wing falling off, or someone trying to fly too high.  A little like thinking because its 4WD you can jump up a vertical 5 ft curb at 60mph.

 

Does anyone make a connector or adapter for this OBD1 port?  There is a lot of Consult type bootleg software out there if there is actually useful data available at that plug.  I'm sure by now you guys would have found such a plug if one exists.  I'd even make up a bunch in China and sell them if I could find one, and it plugged into a helpful reader.  I'll call a couple of places and ask them, like https://www.scantoolshop.com/consult-usb

and http://www.nissandatascan.com/

 

I read all the posts on that link you sent.  Thanks.

 

Yeah, I won't get into body panel removal just yet.  What sealant do you use after you take the fender or another panel off?  I'll get to it sometime I'm sure.

 

I'll do the leakdown test.  I got a fuel pressure gauge for an Explorer but it has a shrader valve on the fuel rail so its a little easier than putting one in line.  Any recommendations?

 

Fortunately (??) timing is checked during the smog test in CA - mine is 15 BTDC and indicates Pass.  This test was done after I did the big work.

 

I've done road tests daily recently.  The puzzle to me is: why I can't get closed loop when stopped.  Closed loop happens immediately I start driving up my street, as soon as I'm moving and not in idle the green light starts flashing.  It keeps flashing all the time, at all speeds unless I'm at idle.  I guess I could put the truck in neutral and be moving and not at idle and see what happens then.

 

After about 15 minutes when driving I get a CEL, and a red fault saved indicator (its a CA requirement I think).  The green light though keeps on flashing as before.

 

If I stop, and park but don't shut off the engine, and try 2000+ RPM sometimes I get a green light, usually but not always on revs decreasing, steady once, not flashing, and then the CEL goes out, and the red light goes out.  Although when I check later, parked, shut off, 45 is still in memory.

 

Have a great day.

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The original consult was a brick type scan tool that plugged into the connector under the dash. Consult II was the one that came out when OBDII came into the scene in 1996. Nissan is currently at Consult 3+ that is loaded into a Panasonic TuffBook.

A quick Google for consult 1 came up with this: https://www.obdinnovations.com/nissan-datascan-i-software-for-1989-2000-consult-i-14-pin-cars/. Might be something to look into. Looks like you will need to get the connector to plug in separate, but found a few listed for less than $25.

Edited by Mr_Reverse
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If you find a legit adapter for the OBD1 port that doesn't cost an arm and a leg, I'd love to hear about it! It could take a lot of the guesswork out of this sort of thing. I was unable to find the right plug end when I did my flashing lights hack and ended up trimming down some blade terminals and hot gluing them into place.
 

The fender has a bit of seam sealer on it from the factory. I didn't bother to reapply it when I put the fenders back on, figuring it didn't do much and would just complicate taking it apart again the next time.

 

Yeah, no easy fuel system test point on these, unfortunately. EF&EC-139 of the '95 manual shows an in-line pressure gauge hooked up between the fuel filter and the rail. Some testers come with a T adapter for this sort of thing. I don't see those adapters sold separately, but I do see similar adapters meant to have a gauge screwed straight into them, so you could just buy that and a gauge if you don't want to buy a whole kit. Just make sure you get the right gauge, the ones for carb setups max out at 15 psi.

 

Stored codes stick around until cleared, whether the fault remains or not. I'm guessing the CEL only illuminates while the ECM senses a fault. The CEL and the red light on the ECM illuminate together (watch the CEL flash with the red light next time you pull codes). My guess, given that it runs fine and cycles normally when driving around, is that it's not rich by much--just a little too much for the computer to compensate for when it's running with no load (again, more load means more air and fuel, which would dilute the effect of a small leak). So you're holding it at 2k, it enters closed loop, it reads rich, shoots for lean, and realizes pretty quick that it can't get there. It stores a code and turns on the CEL. Something about letting off the throttle causes a lean condition, the computer sees the lean condition it's been waiting for, it assumes the fault has resolved itself, and it turns off the CEL. Maybe the fuel cut triggers briefly and the computer mistakes that for the lean condition it's looking for, I don't know.

I'd be interested to try mode 2 and see what that thinks of your mixture when you're driving around.

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9 hours ago, Mr_Reverse said:

A quick Google for consult 1 came up with this: https://www.obdinnovations.com/nissan-datascan-i-software-for-1989-2000-consult-i-14-pin-cars/. Might be something to look into. Looks like you will need to get the connector to plug in separate, but found a few listed for less than $25.

 

Thanks.  Yeah the problem as far as I can understand it is that the port on my truck is a 12 pin, with only about 8 or 9 used, the rest are empty.  I called a few people yesterday about this also, including a very nice guy at M2K who was willing to sell me a Consult 1.

 

Here is what I believe to be the best explanation of the 12 pin port:

 

" The 12 pin connector is for diagnostic tool MST-4987 and is nothing more than an LED box that indicates the state of the various engine solenoids, and also the diagnostic LEDs. "   Its from:  https://www.tapatalk.com/groups/eccstech/australian-d21-t1554.html

 

This would explain why a remote flashing light checker can be wired into this port.  I've also seen this port called a check connector checker port.  I guess its possible that more info can be sourced from this port by the right software or tool, but I have yet to turn up a connector for this 12 pin port.   One thing for sure its not compatible with the 14 pin connectors which apparently were common on most earlier Nissan vehicles other than Pathfinders

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8 hours ago, Slartibartfast said:

The fender has a bit of seam sealer on it from the factory. I didn't bother to reapply it

 

If that's good enough for someone who works on cars to the level you do, its good enough for me!  Thanks.

 

Thanks also for the fuel pressure gauge info.  And your analysis of the closed loop dilemma.  That's what experience allows you to do! 

 

8 hours ago, Slartibartfast said:

I'd be interested to try mode 2 and see what that thinks of your mixture when you're driving around.

 

Yes.  I was under the (mistaken?) impression that Mode 2 would only work when entered while the truck was in closed loop.  Since it only ever gets to closed loop when actively driving I need an extra set of hands to reset to Mode 2 on the fly.  But maybe I can just start off in Mode 2 and once the truck goes closed loop while driving, Mode 2 will function.  We'll see. 

 

Many thanks to both of you. 

 

Have a great weekend

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No worries, Mr R.  I'm learning a lot every day.  Its interesting how standards develop, and frustrating to deal with pre-standards equipment.  I guess there are not really enough of these trucks to warrant making an interface with the complete ECM connection and outputting the data to a connector compatible with the latest Consult and other after market boxes.  I'm sure it could be done, probably in a weekend fueled by pizza, by a group of kids.  I did find one guy who makes an ECM connector with short wires that go directly to another ECM-side connector - allowing one to hook into these connecting wires instead of the harness.  I'm faintly curious which year model Pathfinders had the "big blue" plug ECMs and when they switched to others.  I looked at 2019s and the ECM plugs are completely different.

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On 8/31/2019 at 7:33 AM, paathfinderr said:

Yes.  I was under the (mistaken?) impression that Mode 2 would only work when entered while the truck was in closed loop.  Since it only ever gets to closed loop when actively driving I need an extra set of hands to reset to Mode 2 on the fly.  But maybe I can just start off in Mode 2 and once the truck goes closed loop while driving, Mode 2 will function.  We'll see.


AFAIK it should go into mode 2 whether it's currently in closed loop or not, though obviously it won't tell you much until you get to closed loop. The one time I messed with it, I'm pretty sure I set it while parked and it flashed when I hit closed loop just like mode 1 does.

Someone who was good with coding could probably work out what each pin did (using the service manual) and set up an Arduino or something to take that data and pass it along to whatever type of scanner they liked. There's also a product called Nistune that opens up older Nissan computers for tuning and diagnostics; they don't list the W/D21 ECUs, but they do list other vehicles with the same engine, and My1Path figured the system would probably work even without the M30 ECU swap he did on his. I'm not sure anyone's actually done it, though, and looking at their installation documentation (and price list!), it's not a rabbit hole I'll be crawling into any time soon.

 

And yeah, no shock that the computers in newer models are completely different. I'd be surprised if anything cross-referenced from the newer rigs, other than maybe a few fasteners or trim clips or something.

Edited by Slartibartfast
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The MAF ground was a very common issue for some of these trucks. My first one had the issue and it stalled several times in traffic before I figured it out. I did add the same ground to the terminal and never had another issue. That was the cause of my injector leak code, actually. It is a bit misleading.

 

Depending on what EGR yours has, you might have a tiny rubber hose going from the EGR to the BPT valve (small egr looking thing beside the egr valve). If that hose has a split in it, it will cause issues.

 

If the engine light flashes while driving that could indicate a misfire. I'm not sure these are smart enough to detect what cylinder but be sure your plugs are good and the wires are seated well.

 

It may also just be time for the cat to be replaced. If it is the original one with a lot of miles or was driven with the vehicle running poorly, it will have failed. My brother drove my VW with a misfire for over an hour out of a northern Ontario park before cell service was around, and the cat failed shortly after that.

Edited by adamzan
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On 9/4/2019 at 12:23 AM, Slartibartfast said:

There's also a product called Nistune

 

Thanks.  This is way, way deeper than I want to, or could, go  ?  But reading what My1Path did is unbelievable!  I'm stunned.  I just wanna get my old 92 running and pass smog  ?

 

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On 9/4/2019 at 9:27 AM, adamzan said:

That was the cause of my injector leak code, actually. It is a bit misleading.

 

Depending on what EGR yours has, you might have a tiny rubber hose going from the EGR to the BPT valve (small egr looking thing beside the egr valve). If that hose has a split in it, it will cause issues.

 

If the engine light flashes while driving that could indicate a misfire. I'm not sure these are smart enough to detect what cylinder but be sure your plugs are good and the wires are seated well.

 

Thanks!

 

Yeah, happily I didn't start pulling everything apart looking for leaking injectors immediately after seeing that code!

 

I'll check the EGR hose you mention.  I'd love to find it be something simple like that.

 

Funny thing is, the truck runs really, really well - up hills, on the freeway.  I'd hope that a misfire would show up with crappy performance or a code.  Thanks.  Plugs are good, wires are solidly seated.

 

Once I get it up and running without these funny no closed loop when parked, etc issues I'll get a smog pre test done.  Maybe then it will be time for a cat change, but until these issues are ironed out I can't even think of that step   ?

 

 

 

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On 8/30/2019 at 11:20 PM, Slartibartfast said:

My guess, given that it runs fine and cycles normally when driving around, is that it's not rich by much--just a little too much for the computer to compensate for when it's running with no load (again, more load means more air and fuel, which would dilute the effect of a small leak). So you're holding it at 2k, it enters closed loop, it reads rich, shoots for lean, and realizes pretty quick that it can't get there. It stores a code and turns on the CEL. Something about letting off the throttle causes a lean condition, the computer sees the lean condition it's been waiting for, it assumes the fault has resolved itself, and it turns off the CEL. Maybe the fuel cut triggers briefly and the computer mistakes that for the lean condition it's looking for, I don't know.

I'd be interested to try mode 2 and see what that thinks of your mixture when you're driving around.

 

I removed the MAFS along with its housing (the part which goes from the air filter to the large ribbed intake duct), removed the air filter and its housing and cleaned out everything.  It all looked clean.   I removed the same parts from my 95 Pathfinder and compared the "resistance" of the intake ducting inside the fender on each to either suction or blowing from my shop vac.  I was surprised to notice that for both trucks this inside the fender duct definitely wasn't free flowing.  But the other intake behind and above the headlight was.  So its getting air.  I installed the MAFS and housing from the 95 onto the 92 and did a road test.  It performed identically to how it had with the original MAFS - no closed loop unless its under load, CEL after 15 minutes or so, code 45.   I'm fairly confident the problem is not the MAFS.

 

I started off in Mode 2 and for the most part while driving in presumably closed loop I got synchronized red and green flashing lights, which I believe is alternating between 5% rich and lean as it should.  I'll repeat this road test shortly.

 

I like your analysis a lot.  Thanks.

 

Next I'll look for the EGR to BPT connection.  And run another ground to the exhaust.

 

Then I'll work on the fuel pressure and leak down test. 

 

After that I'll remove each spark plug in turn and look for wetness.

 

My best guess as per your analysis above is a small leak.  Maybe one of those new injectors  ;-(   

 

 

 

 

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  • 1 year later...

Greetings all, 

Well, I'm still on this project (or maybe I should say, back on it).  At this point since my Pathfinder runs pretty well, I'm trying to figure out how to disconnect the CEL.  Other than disassembling the dash and finding the ground or power wire(s) to the CEL harness, or removing the bulb, is there another way?  I suspect/hope the truck might pass an emissions test now, but it will fail for sure if the CEL is on.

Thanks again.

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The CEL is supposed to come on with the other dash lights when you turn the key, so just cutting a wire or removing the bulb would be pretty obvious, and I'm sure it wouldn't be the first time they'd seen it. You could disconnect it from the computer and jumper it to another idiot light that you only see at bulb check, but if the mixture's far enough off that it thinks it has an injector leak, I'd expect the sniffer to notice that no matter what the dash says.

 

I think you were on the right track checking for injector leaks. Better to figure out the issue than waste time (and hack up your harness) trying to hide the issue.

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Hi Slartibartfast,

 

Thanks.  You're right of course.  I can't argue with your logic.  And thanks for the idea of jumpering to another idiot light to avoid the CEL failing bulb check.  I also agree that if the mixture is off that far, the sniffer will likely notice.  If I do try this I'll be careful not to hack up the harness!

 

Changing all the injectors - as I did initially - was a bear of a job, and I'm willing to give almost anything a try to avoid having to redo that.  I only need the truck to pass one smog check in order to complete re-registration.  I'll then either sell it, or take it to a "no smog check" state.  I'd do that now, but I think most states require a valid current registration to re-register there.

 

But thanks for the encouragement to do it right, and for following my posts for so long!  I appreciate it. 

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No worries, and, yeah, I get not wanting to pull it apart again! I had a knock-down drag-out with my brakes a couple years ago and since then I haven't even wanted to think about brakes since then, but I know gonna have to open the system again sooner or later. Good luck with the California smog!

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