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Engine low power

Tiny
BIGJSD
  • MEMBER
  • 1986 NISSAN TRUCK
  • 250,000 MILES
1986 Nissan D21 4x4 4cyl. Cuts out right at 3000 RPM in every gear. Idles fine and runs like normal right until I get to 3000 rpm. At 3000 rpm it begins to act as if it is not getting fuel. When I switch gears it returns to normal until I reach 3000 rpm again. A couple of weeks ago, just for one day, it quit doing it and after restarting it began again. It will need a smog check soon and I need to figure it out before I have it tested.
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Tuesday, February 28th, 2012 AT 10:17 PM

47 Replies

Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 48,363 POSTS
These trucks had problems with the TPS sensor which was more like a switch on the side of the throttle body.

We should run the codes though to see what comes up

https://www.2carpros.com/articles/nissan-obd1-diagnostic-trouble-codes-and-retrieval-procedure-1984-to-1994

This guide can help as well

https://www.2carpros.com/articles/engine-has-low-power-output

If no codes come up go for the TPS sensor

Here is a guide that will giver you an idea of what you are in for when doing the job

https://www.2carpros.com/articles/throttle-actuator-service

Here is what it will be like on your car (below)

Check out the diagrams (Below)

Please let us know what happens.

Cheers, Ken
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Sunday, December 3rd, 2017 AT 4:14 PM
Tiny
HOFFERT88
  • MEMBER
  • 18 POSTS
  • 1986 NISSAN TRUCK
  • 4 CYL
  • 4WD
  • MANUAL
  • 273 MILES
I hav a 1986 Nissan 720 Pickup, Z24 motor, carburated, 4wd, 5 speed. I have been having this problem for quite some time but I can correct it by just reving the engine and letting it drop back to idle. It only happens after the enging is warmed up. While driving, if I take it out of gear to break it will drop to idle then idle will raise a bit then it start loping. If I rev the engine a couple times then let it drop to idle again it will idle fine with out a hitch. If im downshifting while stopping and engine breaking it will start loping maby 50% of the time while just taking it out of gear and not engine breaking it happens maybe 70% of the time. I dont have any loss of power or hesitation while accelerating or any other type of performance loss. It will also start loping if I just start up the truck and let the choke kick in and let it warm up just sitting in the driveway, after it gets to operating temp and the choke kicks off is when it stars to lope. I rev it once and it idles fine, but this truck has done that sence I can remember when my dad drove it. So I dont know what it could be. The carb freshly rebuilt maybe 1000 miles ago so I dont think its that. Just put a brand new air filter so I know is getting plenty of air. The only thing I can think of would be the EGR valve possibly or something in the inner workings of the enging witch im dreading sence this it my daily driver. Please help. Thank you.
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Sunday, December 3rd, 2017 AT 4:16 PM (Merged)
Tiny
CJ MEDEVAC
  • MECHANIC
  • 11,005 POSTS
REBUILT DOES NOT NECESSARILY MEAN "RIGHT"

HAVE YOU TWEAKED THE MIX SCREWS ANY SINCE THE REBUILD--DO YOU KNOW HOW TO DO IT WITH A VACUUM GAUGE OR A TACH/ DWELL METER?

HOW BOUT CHOKE AND HIGH IDLE, ARE THEY ADJUSTED RIGHT? DO THEY MOVE FREELY?

VACUUM LINES HOOKED UP CORRECTLY?

IMMA JEEP CJ KINDA GUY, I KNOW LITTLE ABOUT YOUR CARB OR THE SET-UP.

IS IT STILL ORIGINAL OR HAS STUFF BEEN ELIMINATED OR MODIFIED?

LOOK AT THIS--IT'S FROM BEFORE THIS SITE WAS REMODELED--SOME THINGS LIKE "QUOTES" DID NOT TRANSFER OVER WELL, THIS MAY HELP YOU IN "TRANSLATING" STUFF TO MAKE SENSE

https://www.2carpros.com/questions/jeep-wrangler-1988-jeep-wrangler-engine-issues-when-braking

RETURN WITH A SMILE

THE MEDIC
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Sunday, December 3rd, 2017 AT 4:16 PM (Merged)
Tiny
HOFFERT88
  • MEMBER
  • 18 POSTS
I know it doesn't necessarily mean right. But after the rebuild I had it smoged, it didn't pass (due to a clogged air filter that I mistakenly over looked, read my other post for more info) and had everything checked by another third party tech. He checked the fuel flow everything was spot on, the choke operates as normal as I have known it to be. I think it could be the choke just by the way it sounds but that's what I'm trying to figure out. All hoses are good and hooked up right. The smog shop had messed with them cause they thought they were causing the problem (last time i'll ever go there) and totally fugged it. Had that fixed by the same 3rd party tech. The high idle is just the second barrel valve right? If so iv never heard it called that but yes its adjusted right and opens up when it needs to. Nothing has been modded (yet). The choke is really the only thing I can really think of at this point but haven checked it yet. What's the best way to go about doing that?
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Sunday, December 3rd, 2017 AT 4:16 PM (Merged)
Tiny
CJ MEDEVAC
  • MECHANIC
  • 11,005 POSTS
COULD YOUR FLOAT BE SET TOO HIGH?

OR

NEEDLE AND SEAT DEFORMED OR DAMAGED ALLOWING FUEL IN CONSTANTLY?

DRIVING MIGHT KEEP IT LOWER, WHILE IT'S S. UCKING DOWN THE FUEL.

THEN AT IDLE, FUEL LEVEL RISES AND GETS HIGHER THAN THE VENTURIS

TO SET UP THE SCENARIO (MY THOUGHTS)---FUEL LEVEL TOO LOW FOR SOME REASON, RUNS BUT NOT GOOD----THEN AT IDLE, RISES TO CORRECT LEVEL, RUNS REAL GOOD!----UNTIL FUEL LEVEL IS TOO HIGH, THEN IT BASICALLY STARTS FLOODING, TOO MUCH FUEL INTO THE CYLINDERS. HOW EVER THIS CARB OF YOURS, USES A POWER VALVE (OR EQUIVLENT). MAYBE IT'S ADJUSTED WRONG OR BLOWN (A BACKFIRE CAN BLOW THEM ON SOME CARBS)

I LOOKED AT AUTOZONE AND ADVANCE AUTO FOR YOUR CARB--IT IS NOT IN EITHER. I'M SORTA GOOD ON SIMPLE CAR THEORY, SUCH AS WITH MY TWO JEEPS A '77 AND A '46

I LIKE TO BE "IN COMMAND", RULE OUT COMPLICATED LINKAGES, SO I HAVE MANUAL CHOKES ON BOTH OF MINE.I DECIDE IF IT NEEDS CHOKIN' OR NOT. IF IT WILL DRIVE WELL WHEN I TURN OPEN THE BUTTERFLY. IF NOT I MAY CRACK IT SHUT SOME, TILL I'M AT FULL OPERATING TEMP.

IN FACT TO MAKE MY '77 EZer TO TUNE, GET BETTER MILEAGE, POWER WHEN I DEMAND IT.

I INSTALLED A 4 BBL OFFENHAUSER INTAKE ON MY 258 INLINE 6 CYLINDER. I THEN MOUNTED A HOLLEY 390 CFM CARB ON IT.

TUNING IT WAS DIFFICULT FOR ME AT FIRST, I COULD NOT "READ THE PLUGS" WORTH A CRAP, WHEN I SHUT HIM DOWN COASTED TO THE SIDE OF THE ROAD TO PERFORM A "PLUG CUT" TO DETERMINE WHAT SIZE JETS TO USE.

I FINALLY FOUND THAT I COULD INSTALL A OXYGEN SENSOR CLOSE TO MY HEADERS, AND USE IT TO RUN A AIR/ FUEL RATIO GAUGE.

THE GAUGE DISPLAYS IN LEDS. LEAN, STOICH (JUST RIGHT), AND RICH.

IT FLUCTUATES AS YOU DRIVE UNDER DIFFERENT CONDITIONS. FLAT ROAD AT 55 MPH IS WHAT I SELECTED MY BEST JETTING FOR. MY "IN DASH" VACUUM GAUGE ALONG WITH MY AIR/ FUEL GAUGE HELPED ME SELECT A "POWER VALVE" TO TWEAK IT ALL TOGETHER.

THE NEWER BELLS AND WHISTLES ALONG WITH SMOG CRAP BLOWS MY MIND! I'M SORRY I CANNOT HELP MORE.

EVEN W/ SIMPLE CARBS, I HAVE FOUND THAT THERE ARE FEW WHO TALK THE TALK AND WALK THE WALK. MOSTLY "JUST TALK" AND COBBLE THE REST OF IT UP. I DO MY OWN WORK, BUT I DO ASK THOSE WHO "SUPPOSEDLY KNOW", FOR INFORMATION, I'M PRETTY GOOD AT "CENSORING OUT" THE "WANNA BE'S" MIS-INFORMATION, I DO READ ABOUT MY OWN SYSTEMS, AND TRY HARD TO FIGURE STUFF OUT "CORRECTLY" ON MY OWN. I DO NOT LIKE "I THINK", I WANT THEM TO BACK UP THEIR ADVISE WITH FACT--THAT CAN BE FOUND IN PICS OR TEXT---PROVEN.

IF YOU CAN ELIMINATE SMOG STUFF (NOT CHECKED IN YOUR AREA) MAYBE AN AFTERMARKET SIMPLE TYPE CARB MIGHT DO YOU BETTER. I HOPE I'M NOT WASTING YOUR TIME.

LET ME KNOW HOW IT'S GOING

THE MEDIC
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Sunday, December 3rd, 2017 AT 4:16 PM (Merged)
Tiny
WLJCA07
  • MEMBER
  • 1 POST
  • 1986 NISSAN TRUCK
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 150,000 MILES
Engine Performance problem
1986 Nissan Truck 4 cyl Two Wheel Drive Automatic 150000 miles

My D21 fuel injected motor will idle fine but after I put gas in it, the motor pulses and lurches like it isn't getting proper gas (when I am trying to drive, not sitting at idle). It has been below zero here for a few days so I put 2 pints of dry gas in the tank thinking there was water in the fuel that had frozen. I have also let it warm up for a long time thinking something else under the hood is frozen. It is a little warmer today (15) and it is still doing the lurching like it is going to stall but it doesn't stall. HELP!
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Sunday, December 3rd, 2017 AT 4:16 PM (Merged)
Tiny
ISLAND_PRIDE71
  • MEMBER
  • 62 POSTS
When did you last give it a tune up and an oxygen sensor replacement and fuel filter? I strongly recommend you check the fuel pressure.

Also check the A/F ratio solenoid
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Sunday, December 3rd, 2017 AT 4:16 PM (Merged)
Tiny
TRPLSIX4U
  • MEMBER
  • 1 POST
  • 1986 NISSAN TRUCK
  • 4 CYL
  • 2WD
  • MANUAL
  • 300,000 MILES
Engine Performance problem
1986 Nissan Truck 4 cyl Two Wheel Drive Manual 300000 miles

I got the computer wet and replaced it. Before replacing and scince when I turn the key to the on posision fuel sprays into the carb at high pressure and gets into my oil some how. What is causing the high pressure fuel spray?
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Sunday, December 3rd, 2017 AT 4:16 PM (Merged)
Tiny
BUDDYCRAIGG
  • MECHANIC
  • 2,262 POSTS
God, it's been like a million years since I had to work on one of those.

I seem to recall that there was some computer module under the dash on the passenger side that went bad and would cause that.
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Sunday, December 3rd, 2017 AT 4:16 PM (Merged)
Tiny
DEANDOG84
  • MEMBER
  • 1 POST
  • 1986 NISSAN TRUCK
  • 4 CYL
  • 2WD
  • MANUAL
  • 190,869 MILES
Engine Performance problem
1986 Nissan Truck 4 cyl Two Wheel Drive Manual 190869 miles

when I push the pedal down to the floor all exceleration stops. When I release the pedal halfway it will putter and I have exceleration again. It does it in neutral when I reve the motor. PLEASE HELP! THANK YOU$
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Sunday, December 3rd, 2017 AT 4:16 PM (Merged)
Tiny
MHPAUTOS
  • MECHANIC
  • 31,937 POSTS
Hi there, is this a carby or a injected engine?

Mark (mhpautos)
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Sunday, December 3rd, 2017 AT 4:16 PM (Merged)
Tiny
MICHAEL.LATHROP
  • MEMBER
  • 2 POSTS
  • 1985 NISSAN TRUCK
  • 4 CYL
  • 2WD
  • MANUAL
  • 170,000 MILES
85 nissan 2wd pickup. 1st and 2nd gear fine. When shifting to 3rd and giving pedal to get up to speed, it bogs down like its running out of gas. Any answers?
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Sunday, December 3rd, 2017 AT 4:16 PM (Merged)
Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
You sure it's not coming from a slipping clutch? Probable causes could be one of the following below

Oxygen sensor.
Catalytic converter.
Fuel injectors dirty/sticking.
Mass airflow sensor/Airflow meter.
Throttle position sensor.
Crankshaft position sensor
Knock sensor
Manifold absolute pressure sensor.
EGR Valve
Fuel pressure regulator leaking or defective fuel pump.
Fuel contamination.
Foul/defective spark plugs.
Open spark plug wires.
Ignition coil/Coil packs defective.
Incorrect ignition timing.
Cap and rotor.

Note:If it doesn't apply disregard it and keep testing.
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Sunday, December 3rd, 2017 AT 4:16 PM (Merged)
Tiny
MICHAEL.LATHROP
  • MEMBER
  • 2 POSTS
Definitely not the clutch. Thanx for your other suggestions. I planned to try replacing the fuel pump this wknd. Any particular "firsts" I should ck?
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Sunday, December 3rd, 2017 AT 4:16 PM (Merged)
Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
Go with the TPS and airflow meter
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Sunday, December 3rd, 2017 AT 4:16 PM (Merged)
Tiny
CACTUS50
  • MEMBER
  • 13 POSTS
  • 1989 NISSAN TRUCK
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 139,000 MILES
My 89 nissan D21 Z2.4 with automatic seems to be in the "limp home" mode. Engine does not rev normally and transmission shifts hard - much like the old auto's with a bad vacum modulator. It starts and runs smoothly, but has reduced power, poor acceleration and poor fuel economy. In checking the wiring I found wires from what appears to be the thermostat housing that are tied together. There is a plugin connector that looks like it would have connected to the "connected" wires from the thermostat. Why would someone do this?
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Sunday, December 3rd, 2017 AT 4:16 PM (Merged)
Tiny
WRENCHTECH
  • MECHANIC
  • 20,761 POSTS
The thermostat is not electrical in any way. You might be looking at a temp sensor or something and if so, that will have a major effect on you fuel mixture.
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Sunday, December 3rd, 2017 AT 4:16 PM (Merged)
Tiny
CACTUS50
  • MEMBER
  • 13 POSTS
There is also no power to the wire going to the base of the distributor, so if a sensor is disconnected does the system default to the "limp' mode?
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Sunday, December 3rd, 2017 AT 4:16 PM (Merged)
Tiny
WRENCHTECH
  • MECHANIC
  • 20,761 POSTS
In some cases it will ignore the sensor reading and substitute a default reading for it but not all sensors or computers are programmed that way.
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Sunday, December 3rd, 2017 AT 4:16 PM (Merged)
Tiny
CACTUS50
  • MEMBER
  • 13 POSTS
Checked the wires a little closer and they go to a temp sensor below the thermostat housing. Also, they are not wired together but directly to other wires without a plug. Which sensor/s would be suspect here?
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Sunday, December 3rd, 2017 AT 4:16 PM (Merged)

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