# 1988 Nissan SE V6 pickup bogs, breaks up, blows black smoke?????



## chuckb (May 15, 2005)

My 88 V6 5speed has 154000 miles. Ran great then all of a sudden started acting like cat was clogged up. Started breaking up then bogging so bad I could barely get it off road. Got it towed, it started back up and ran fine, then slowly went to crap again. 

I have changed fuel filter, done compression check, gutted cats, changed plugs(which were black), replaced coil(but NOT the ignition module attached to coil) and it still does it. 

it acts like it's running real rich, missing and bellowing black smoke.

any idea what it could be? thanks


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## heathman (Sep 13, 2010)

I would suspect a pre cat oxygen sensor stuck lean ... this telling the computor to add gas, resulting in overfueling (black smoke). Good Luck !!!


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## chuckb (May 15, 2005)

^thanks. is that common for these trucks?


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## heathman (Sep 13, 2010)

It is common for any vehicle, you can scope the 02 to see it's performance working on a 1.0V scale.... (switching between .001V to .9V quickly ... if not it is lazy and will require replacement..If that looks good I would also suspect a M.A.F sensor ... Good Luck !!


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## chuckb (May 15, 2005)

thanks. anyone else have any suggestions before I throw a $120 O2 sensor at it?


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## chuckb (May 15, 2005)

well, it wasn't the O2 sensor.


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## jdg (Aug 27, 2009)

Change the ignition module. Those things like to do stupid stuff like that and start failing when they get warmed up.
Don't know why you threw an O2 sensor at the problem. You could've disconnected it, kept it from messing with the ECU, and checked how the truck drove without it. Simple, and sometimes, effective way of isolating a bad O2 sensor.
I'm not saying everybody suggests a bad O2 sensor whenever they hear of a computer controlled engine not running right, but that's what it seems like to me.


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## chuckb (May 15, 2005)

jdgrotte said:


> Change the ignition module. Those things like to do stupid stuff like that and start failing when they get warmed up.
> .


the module that is attached to the coil?
that has gone bad twice before in the 12 years I've owned the truck. before when it went bad the tach would jump around and then the truck would just shut off. now if just runs like crap.
I may change that module but I'm getting tired of throwing money at a $600 truck....


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## jdg (Aug 27, 2009)

That's a good sign right there...the tach jumping around, since it gets it signal from the back side of the coil, well one of the places it could get it's signal anyways. Don't know why those things just "decide" to kick the bucket, but they do. I keep a spare module handy for almost everything I got (Nissan, GM HEI, Dodge truck, etc) just for that reason. Junkyard parts, but they might dig me out of a jam someday.
It's either throw a few bucks at a cheap truck, or throw a buttload of money at a dealership and insurance company on a new truck. I'm all about keeping that $$$ in my pocket. Good luck...


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## chuckb (May 15, 2005)

jdgrotte said:


> That's a good sign right there...the tach jumping around, since it gets it signal from the back side of the coil, ...


that's the thing, the tach is NOT jumping around this time. that's why I'm leary to go spend another $100 on a module...


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## jdg (Aug 27, 2009)

Heck, who knows... Maybe the tach isn't jumping around _YET_ but will eventually.
One out in the woods thought I just had...maybe the tach is a bit older nowdays, a bit 'grimier' on the inside, and the needle can't respond quick enough to those jumps like it used to... I dunno, and I can't think of any way to test the theory short of pulling the module, putting it in an oven until it's good and hot, putting it back in and see how it runs on a cold engine/hot module start, except for maybe hitting it with a hair dryer or something.


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## chuckb (May 15, 2005)

well it wasn't the module either....... I'm about to throw this truck in the garbage.

anyone else with other suggestions?


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## tulaviok (Sep 7, 2010)

so if my rpm is jumping all the time i need to change my ignition module ?? ..i have no problem with the truck...never stop but my rpm is going crazy sometime


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## jdg (Aug 27, 2009)

chuckb said:


> well it wasn't the module either....... I'm about to throw this truck in the garbage.
> anyone else with other suggestions?


I suppose it's entirely possible that the ECU is about ready to give out for good.
Troubleshooting stuff like this is a bee-otch to say the least... I don't know what else to say except, since it's already running like crap, start pulling stuff apart... (of course that's probably the most useless piece of advice for the day eh?)


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## CMax03 (Jan 17, 2009)

fuel injector(s) stuck in the open position!


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## jdg (Aug 27, 2009)

jdgrotte said:


> Troubleshooting stuff like this is a bee-otch to say the least... I don't know what else to say except, since it's already running like crap, start pulling stuff apart... (of course that's probably the most useless piece of advice for the day eh?)





CMax03 said:


> fuel injector(s) stuck in the open position!


I stand corrected...


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## chuckb (May 15, 2005)

CMax03 said:


> fuel injector(s) stuck in the open position!


I don't think so because when you first start it it runs ok for about 5 minutes then gradually gets worse until it can't even move under it's own power.


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## jdg (Aug 27, 2009)

That's what I meant (well, not really, if you kinda read between the lnes in post #16)...
If a fuel injector was stuck in the open position, a number of things would happen, aside from the black smoke/chugging, etc.
For one thing, when the engine is shut off, residual pressure in the fuel line would bleed off thru that injector(s), possibly partially filling that cylinder and cause a hydro-lock condition (i.e. bent rod, no start, etc).
If that didn't happen, the fuel that is sitting on top of the pistons would likely run down past the rings into the oil and just cause a mess overall.

Have you put an ohmmeter on either the Intake Air temp sensor (if equipped) or Coolant temp sensor (which basically simulates a choke by adjusting fuel delivery according to engine temp) ?


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## CMax03 (Jan 17, 2009)

Measure the resistance then @ 180 degrees F and check I/A/W the FSM.....if it was the coolant temp sensor it would be hard to start in cold weather.....


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