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Smoke from exhaust, stuttering and loss of power only on long climbs


Macklen

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Hi there.
New to this forum, but I have been chasing this issue for a while now at the NICO club forums. Figured it was time to get it to the real pros *wink wink*

Z24, Hitachi stock carburetor. Runs great on plain terrain, starts and idles like a champ, doesn't regularly smoke or stall.
But during long climbs, it will lose power, begin to stutter as if it wants to stall and white smoke will come out of the pipe. I get a smell of raw fuel when it does. I wanna say that the carb floods somehow as the throttle is pressed during the climb, but I'm not certain.

Now, the main problem is that the condition goes away on its own. It can run great for months, then start running like crap again.

So far, I've changed spark plugs, cap and rotor, wires, fuel filter, fuel pump, set timing, re-soldered fuel pump relay behind the glove box. Sometimes the problem goes away when I do something, but then it comes back and the previous "solution" does not work.

All the emissions hoses are removed and ports capped except for the vacuum advance. EGR and tube still on, but ports on EGR are capped.

The last time I had this problem, I removed the AB valve from under the air cleaner and capped the port and it ran great -after some adjustments to the idle- until an unrelated tranny issue popped up and it sat for about a month. Got the tranny fixed and now this other thing came back. Truck won't climb.

In concrete, my main questions are:

- What would cause the stutter, unburned fuel smell and white smoke only on climbs?
- Why would the problem be intermittent, i.e. runs great for months, then starts to run like shyte, then runs great again, regardless of what I do or don't do?

I figured I'll check the timing again, try to mess around with the mixture screw at the carb.
Maybe running rich, thus flooding when under throttle?? Maybe remove the EGR altogether and plug the manifolds, would that even be related??

At this point, I'm running out of ideas. I wanna replace the carb with a Weber, but I want to make sure first that this particular problem is at least addressed before I order one. Maybe I don't need a new carb, since the truck runs great when this issue is not showing.

Thanks.

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White smoke is from burning oil. Black smoke is from too much fuel(too rich). Try disconnecting the vacuum from the distributor and drive it. Also look for oil in the distributor. I'd say it sounds like your sucking oil into the engine from a vacuum line or leak. What does it do going down a hill?

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White = coolant, black = fuel, blueish white = oil. (generally..)

 

 

Hitachi carbs are known to be shit, When it happens.. stop, go smell the exhaust. If it's sweet, its coolant. Otherise, it's going to smell like burnt oil, or raw fuel like you mentioned.

 

If you wanted to safe yourself some money, you could just pop that hitachi off.. toss a rebuilt kit at it and try again. Otherwise, weber and be done.

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White smoke is from burning oil. Black smoke is from too much fuel(too rich). Try disconnecting the vacuum from the distributor and drive it. Also look for oil in the distributor. I'd say it sounds like your sucking oil into the engine from a vacuum line or leak. What does it do going down a hill?

Down hill or plain ground it runs great, no smoke whatsoever, no stutter, no weird idle or noises.

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u sure white smoke is burning oil? to the orig. post did u do a compression check

No compression check yet, it is however on my list.

I did suspect worn piston rings, but it does not smoke all the time and the problem even goes away at times.

Wouldn't a ring issue be always present no matter what I did? Remember the truck spends weeks sometimes without suffering any symptoms and climbs reasonably well during these times.

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White smoke is from burning oil. Black smoke is from too much fuel(too rich). Try disconnecting the vacuum from the distributor and drive it. Also look for oil in the distributor. I'd say it sounds like your sucking oil into the engine from a vacuum line or leak. What does it do going down a hill?

 

Intake and vacuum advance are at their lowest at full throttle.

 

 

To check fuel level look at the round sight glass on front of carb. Should be at the center. Under hill climbing conditions you are using more gas and the carb may go empty if the float is set too low.

 

 

Are you adding coolant because it is always down slightly?

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like i said do a compression check, if 2 cylinders are low, then suspect headgasket. also check ur dipstick and if oil looks milky or like choc. milshake then head gasket. maybe u live in a cold area and common for engine to smoke white when cold.

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Intake and vacuum advance are at their lowest at full throttle.

 

 

To check fuel level look at the round sight glass on front of carb. Should be at the center. Under hill climbing conditions you are using more gas and the carb may go empty if the float is set too low.

 

 

Are you adding coolant because it is always down slightly?

Not really. I check levels regularly and coolant is always the same. Coolant's good.

 

I did do a head gasket about a year ago, and I assume it was successful, since there has been no coolant in the oil or vice versa. Besides, this particular issue with the power loss and stuttering on climbs had happened before the gasket blew, so I think it's not related to that work.

 

As for the smoke from the pipe, I couldn't swear to it being white white, but it looks clear in the mirror. Never really stopped to see it closer, all I want when it happens is to get to the top of the climb. But I do notice the smell of unburned gas when I get to the top.

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Next time the engine is cold, I mean over night not started, cold, remove the valve cover and re-torque the head bolts. Be dure you only loosen and tighten one bolt at a time. Loosen fully and immediately tighten to 60 ft lbs. The Z24 is prone to HG failures every 100K and the preventative measure is to re-torque the bolts every tune up (or once a year. Try it... it costs nothing.

 

Equally unlikely...... how is your oil level? Not over full?

 

Do you have a round 6 wire connector at the back of your carb?

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Next time the engine is cold, I mean over night not started, cold, remove the valve cover and re-torque the head bolts. Be dure you only loosen and tighten one bolt at a time. Loosen fully and immediately tighten to 60 ft lbs. The Z24 is prone to HG failures every 100K and the preventative measure is to re-torque the bolts every tune up (or once a year. Try it... it costs nothing.

 

Equally unlikely...... how is your oil level? Not over full?

 

Do you have a round 6 wire connector at the back of your carb?

Oil level is good too. No signs of coolant in it. Oil does tend to darken over time, but not to tar level, so I simply assume that all old motors do that.

There is such connector, but not all wires are connected, some are cut. I'll have to get back to you on the colors of those that are still connected.

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I have an LZ23, one morning I was late and in a big hurry, but was a quart low on oil, so I added a bunch of oil, called it good and got outta there fast, now I haul a trailer around most the time so I have to put my foot a little deeper into the pedal even on level ground, well I noticed a cloud in back of my truck on the hiway, when I let off it quit smoking, if I floored it it was better, but if I wanted to go a steady speed, it smoked real bad, and I mean get stopped and get a ticket bad.

After I got home that evening smoking all the way home on the hiway I checked the dip stick and seen it was a little over filled, I emptied a little out buy removing the drain plug in the oil pan and it didn't smoke anymore.

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So 6 wire plug or two????.

 

Six wire plug would indicate a mixture feedback carb. They need an O2, temp, throttle position and ?? other sensors for the ECU under the seat to adjust the electric solenoid main jet for optimal air fuel ratio. If these sensors are cut out or disabled, the ECU will go into 'limp home mode' This is an over rich condition to prevent an accidental over lean condition that might damage the engine so you can drive it to be serviced.. It will run poorly and give terrible mileage.

 

The feedback carb is basically halfway between a carburetor and fuel injection. 

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I forgot to say... any order front to back, side to side anything you like, BUT only one bolt at a time.

Will do that tomorrow.

 

Forgot to mention in the original post, maybe relevant. The truck may start the day great. I take the same route to work -construction- everyday and sometimes it will do great in the morning and crappy on the way back, same road, same hills. I also notice it starting to lose power if I'm stuck in traffic for a little while -brake, advance, brake, advance, brake...- Never overheats or anything, just grows weaker and then smokes on the climbs.

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So 6 wire plug or two????.

 

Six wire plug would indicate a mixture feedback carb. They need an O2, temp, throttle position and ?? other sensors for the ECU under the seat to adjust the electric solenoid main jet for optimal air fuel ratio. If these sensors are cut out or disabled, the ECU will go into 'limp home mode' This is an over rich condition to prevent an accidental over lean condition that might damage the engine so you can drive it to be serviced.. It will run poorly and give terrible mileage.

 

The feedback carb is basically halfway between a carburetor and fuel injection. 

It is a 6 wire plug, but some wires are cutoff, I think only one goes all the way to the carb. Going from memory, I'll be able to make sure later today. This might support the "Go Weber" party line, huh?

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Maybe a weber but first check the intake mounting. I think the base of the mixture feedback carb is different from the regular Z24 carb. If ordering a weber be sure they know this and send the correct adapter.

Great man. I will do the bolts and check those wires tomorrow, take and upload some pics for future reference on the site.

I don't mind changing the carb, it just would suck to do that and then have the same shyte happen. But your explanation makes a lot of sense, this truck has been in the hands of butchers before and god knows which sensors work and which don't. I figure simplest is best.

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I re-torqued the head bolts, drained about half a quart of oil (it was right at the top mark, I wanted to make sure it was not this as someone suggested) and I fiddled a bit with the idle and mixture, got it running decent, no problems so far, but it has done so before. Like I said problem goes away and comes back. In the meantime, took some pics of my carburetor, which looks indeed pretty messy.

This is the 6 wire plug that goes to it:

20161016_151334.jpg

The only wire that's not cut connects here:

20161016_150827.jpg

There are other wires that go to the carb, no clue what they do, but they are all connected solidly.

20161016_150855.jpg

20161016_151308.jpg

The carb looks messy in general. I don't have much time with the truck, but I am trying to get it back to as good a shape as possible, being my workmule. I have not ever worked on a carburetor before.

I noticed that one butterfly valve, not the one that's beneath the choke flap but the other one on the drivers side, does not open when I activate the throttle cam by hand. Also, only the jet under the choke flap sprays any gas in the carb barrel, the other looks dry, valve never moves. I noticed that this butterfly valve is operated by vacuum, by an arm that goes to a couple of dashpot looking things on the drivers side of the carburetor. Any comments on how this should operate?

20161016_151030.jpg

It does appear that I'd benefit from a new Weber after all.

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I'm not convinced that is the correct carb. It's been modified for sure. The BCDD is missing and it looks like a factory cover plate. This carb may be off of a different car maker and not even Nissan. The emissions hoses and several sensors have been deleted so no telling what could be wrong.

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I wouldn't swear that it is the original carb, but I think it looks fairly close to others I've seen in the forums, it maybe the weird angles I took the pics from to get the wires that makes it look odd.
It may be time to bite that bullet and buy a new carb. May my Odyssey live on in the Ratsun forums and perhaps help a fellow in need at some point, :thumbup:

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Similar yes. That solenoid with the fitting at the front, I have never seen before. The BCDD has an extremely clean and well fitted block off plate that seems factory. No vehicle after '74 that had a carb didn't have a BCDD on it.

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