1994 Land Cruiser misfire (3 Viewers)

[Armandojavierl]

I need some advice.

I have a 1994 Land Cruiser (US Model 4.5 6Cyl) since i got it, it has a little misfire that became worst with time, there used to be a check engine light which was calling for a rear knock sensor (i think the number was 54?), replaced with a cheap autoparts new knock sensor and the code left but it came back after a few days of driving. I repeat that process 2 o 3 times thinking i was getting a defective knock sensor.

I Ignored the issue and focus on other stuff like wires, ignition coil, spark plugs etc. Kept driving it and off-roading it ignoring the misfire which comes and goes. At this point the misfire its still not happening all the time, but when its there its far worst. A bunch of stuff has been replaced including a new oem toyota knock sensor. Theres no check engine light at all even when its misfiring. Im going crazy at this point but i dont have a lot of experience with older vehicles (this is my oldest) hoping im just making a rookie mistake.

I’ve replaced the following parts since i got it.
-Ngk blue wires
-oem toyota spark plugs.
-rear knock sensor toyota oem
-in-tank fuel pump delphi with filter (twice)
-fuel filter close to the engine (twice)
- rotor and cap toyota oem.
-ignition coil
- ignition contacts inside the rotor and cap with sensor.
-clean throttle body
-clean idle air control valve
-clean AFM
-tape intake boot
-pour some fuel injector cleaner in the tank.
-pcv valve replaced
-2 brand new o2 sensors relocated to manifold.
-water pump aisin
-fan clutch aisin blue
-all pulleys
-toyota v belts
-radiator with cap and fresh coolant
-thermostat aisin
-relays

The misfire its really hard to explain since its not always there. You start accelerating slowly and can feel the truck struggling before hitting 1600-1700, after that the misfire “disappears but if you keep the gas pedal a 2k rpm it will slowly go down like its not stable. Cold or hot you can be driving and it will start struggling, misfire and turn off. You turn it off and on again and most of the time goes a away and comes back later.

 

[CharlieS]

Pretty sure the one you pointed to in your picture is the AC high temp cutoff sensor. That's not the one that feeds the ECU.

Front to back they are the dash temp gauge sensor, the AC high temp cutoff sensor and the ECT temp sensor for the ECU.

I learned the hard way to not use aftermarket ECT sensors. Stick with Toyota parts.

 

[TWILLY]

I had a similar problem and it turned out to be a rusted vaccuum tube inside the vaccuum hose between egr valve and throttle. I never saw it until the hose was expanded and split due to the rust build up. Haven't had that misfire symptom since.

I did too. Cleaning / replacing egr components resolved it. It was a misfire and stumble under hard throttle.

 

[ZackR]

Check the wiring harness where it passes the EGR pipe. Tons of threads on how intermittent shorts inside the harness can cause what you are describing.