# '84 4 cyl. REALLY crappy mileage



## oldnluvinit (Dec 22, 2008)

I'm new to this. Here's the short run-down:

My son was given an '84 nissan 4 x 4 p/u a couple of weeks ago for his 16th birthday--gift from grandpa. The truck apparently sat for over a year down in TX (location is now mid missouri). It's the 4cyl 2.4 liter, 5 speed manual--about 204K on it. I've installed new alternator, battery, water pump and fan clutch, thermostat, belts, and radiator hoses. Truck has new gas tank--but sending unit is bad. On order. Will get installed in a couple of days. A/C has been removed by previous owner.

So far, this thing hasn't gone over 72 miles on 15 gallons of gas--roughly 4-5 mpg. Told ya it was crappy.

Here's the kicker: It runs like a top. No smoke. No miss. No stall. Idles smooth with no "ramping" or revving. Like others, it's a little hard to start in this 7deg weather, but will start and run great. This is a carbuerated model--grandpa had a new carb put on before he gave it to my son (along with new clutch and tranny re-build). The fresh air intake and blow-by tube to the breather are completely gone. Could this be causing this severe an issue? This just seems to be too bad a problem for a fowled plug or dirty air filter. Seems to me like more of an air/fuel mix issue but I'm no mechanic. Idles at around 800rpm, but tach is a little quirky. 

Has fresh oil change. Oil smells very slightly of fuel, but I can't be certain.

Haven't really had it on the highway to see how HP performs yet. I'm having the timing, choke, and vacuum advance checked tomorrow by a local mechanic, but I just feel like I could chase this thing from bumper to bumper and spend a lot of money without fixing anything. (Yes, the front hubs are unlocked O2 sensor? Catalytic converter? Any thoughts?

Any help given would be greatly appreciated!


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## zanegrey (Dec 5, 2005)

the intake and exhaust pugs should be 2 different types.
check choke operation.
check brake drag.and tire infaltion..
check carrier bearing for drag.

since it has had carb work done .. check float and fuel pressure regulator


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## oldnluvinit (Dec 22, 2008)

Thanks zane. I really appreciate the tips.

By carrier bearing, do you mean in the clutch? I can't hear it from inside the cab, but from outside I can hear a very light "squeal" when he depresses the clutch. Now that I think about it, from inside with clutch depressed--in gear or neutral either one--it's actually pretty quiet. But in neutral there's a bit of a "hum" when I let off the clutch.


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## zanegrey (Dec 5, 2005)

the carrier bearing is on the drive shaft ..

the squeal is probably the throw out bearing.. by gently removing the boot on the slave cylinder and shinning a lite up so you can see the tob , i sprayed mine down with a silicone lubricant to stop the squeal.


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## SPEEDO (Jun 9, 2003)

The carrier brg or the driveshaft support brg...(in the driveshaft going to the rear diff) 
You said it has a new carb.. has it been adjusted at all??? the jets might be a little too big for the application, might try re-jetting. If it takes awhile to get up to speed I would look at the cat. Might also change the fluids in the diffs, might be a little thick (if you havent already) You have about 10mpgs hiding somewhere....


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## brookwood61 (Aug 18, 2005)

I had those carbs on an 82 & an 85. They are great. Check the site glass, for fuel level. There is a dot where the fuel level should be. If it is above the dot, adjust you floats. I always started both adjusting screws at 1 turn open, then adjusted to the highest vacuum.
I can't remember if a 4WD 720 has a carrier bearing. It's freexing rain right now, so heck with going outside to look. Some can set me straight on this for sure. I know it has the shorty center driveshaft. I'm not trying to sound like a smart [email protected]@, but I really can't remember if it has a carrier bearing.It's been about 7 years since I replaced the U-Joints. I know my 61 Chevy has 1,you should hear that noise when it lets loose.
Good Luck


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## SPEEDO (Jun 9, 2003)

yes, it does have a carrier brg...


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## rockcrusher44 (Oct 7, 2006)

new o2 sensors, remember you have two, one at the exhaust man. and one at cat. converter and a new cat converter. my 97 started getting poor gas mileage a few weeks ago. i changed both sensors and the converter and that bumped me back up to around 19 MPG.


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## brookwood61 (Aug 18, 2005)

Thanks for the reply Speedo.I finally quit raining,so I snuck out and took a look this morning. I don't have a carrier bearing in the rear.So if your truck is like mine,a seperate tranny and transfer case with 3 driveshafts-maybe check the transfer case bearings. If I remember right,there was a problem with many of these transfer case bearings. That would cause you drag too-but you should also feel a vibration. A binding center drive shaft would do it also-but it should also shake the whole truck,like a wet dog.
Good Luck


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## oldnluvinit (Dec 22, 2008)

Hey, thanks to all who pitched in their advice. I had the truck in the shop. Carb was way out of adjustment, some timing issues, vacuum issues, so on. Unfortunately, Christmas nite some SOB blew a stop sign and T-boned my son in this truck.

New problems now. Any interested parties please refer to the new string I'm starting.


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## SPEEDO (Jun 9, 2003)

Hope everyone is alright!


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## biddyboo (Dec 29, 2008)

*need help on converting older 2.4L motor into 91 truck*

i have a 91 2.4L and its finish. i also have 84 2.4L motor which runs great. can i use it in the 91 but use all the stuff from 91 motor to make it work? (intake, injectors and all the wiring?)


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## zanegrey (Dec 5, 2005)

not as a long block swap..

but you can swap the91 as a whole engine in and its mounts to include the wirehrness and ecm. it is a lot of work ..

you would be better off with less trouble using the z24 from 84 to 89 ..long block.


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## biddyboo (Dec 29, 2008)

if i strip the motor down on the 84 and use the outside of the motor on the 91 could i make my truck run? and if its too much work, whats the work thats too much? lol


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## zanegrey (Dec 5, 2005)

the 84 and 91 have different bolt patterns for the intake and exhaust manyifolds.

the 84 is a 2 coil sysytem and the 91 is a one coil sys.

the ecm are completely different as well ..


but if you really are going to try then u need to speak to datsunmike on Ratsun Forum - Powered by vBulletin


he is one of the fore most experts on mixing and matching nissan parts..


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## biddyboo (Dec 29, 2008)

*thanks*

thank you very much. i get it now lol. what nissan motor years can i use that would fit in my 91? also since you mentioned the z24 motor, would fit in my 91 truck and how much work would it take to put it in?


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## zanegrey (Dec 5, 2005)

90 thro 95 is the ka24e engine and is a direct fit for a 91.

84 thru 89 is the z24 ..

a z24 in a 91 is going against evolution but the whole wirehaness and ecm must be brought over along with peripheals.

unless you go with an aftermarket intake and ingintion system


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## oldnluvinit (Dec 22, 2008)

Speedo,

Thank you, sincerely. I failed to mention but yes, thankfully, no serious injuries. They got bumped around real good so they're a little stiff and sore. Otherwise, just scared stupid.


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