Intermittent power loss 91 landcruiser

[Flylow 72]

91 Landcruiser, 167k. Sat for 8 months, started right up drove for 700 miles no problems. Now after warm up or roughly 2 mile drive, rpm will drop to idle when it reaches 1400-1600. Will actually stall and engine will quit when driving sometimes. When vehicle is parked rpm will just drop from 1400-1600 to idle and engine won't stall. No CEL.

What has been done: I'm including everything since we fired it up in Nov., to leave no stone unturned.

Added fuel injector cleaner

Replaced: starter
inline fuel filter (found h20 on pump side of line)
fuel pump
distributor cap, rotor and harness

I have read quite a few posts on here with regard to these types of issues, and I believe some lucky 80 owner has experienced this same problem, unfortunately posts often end with no resolution. At any rate vehicle is located on the North Shore of Kauai, anyone who has been here would know resources are limited.
Any ideas will be greatly appreciated.

 

[Parsnip]

key on engine off back-probe the throttle position sensor and verify it moves smoothly from almost zero volts throttle closed to almost 5 volts throttle open. An analog volt meter is best or a digital with a bar graph.

 

[Flylow 72]

key on engine off back-probe the throttle position sensor and verify it moves smoothly from almost zero volts throttle closed to almost 5 volts throttle open. An analog volt meter is best or a digital with a bar graph.

I should have mentioned I am no mechanic. Could you please give more detail about
"back-probe the throttle position sensor". I apologize for my ignorance in this matter, just dumb it down a bit.

 

[Parsnip]

No worries mate.

The TPS is opposite the intake from the cable that moves the throttle plate.

The TPS has three wires. One is always 5 volts. One is always ground. One will change voltage based upon the position of the throttle.

by Back-probe I mean leave the sensor connected to the harness and push the probes of your meter into the connector from the rear. If the probes are too thick then make up little probes using the copper out of a cable TV (RG6 for example) cable and connect your meter's probes to those wires sticking out of the connector.

 

[Flylow 72]

Ok, I will give that a try and post my findings. Thank you.

 

[Flylow 72]

Alrighty, here is what I'm looking at. Three green wires and one brown. Which one gets the back-probe?

 

[Parsnip]

TPS schem

• Parsnip
• Dec 26, 2015

Green Black (2 G-B VTA on diagram) on the schematic is the wire that should vary its voltage with throttle position.

 

[Flylow 72]

Again thank you.

 

[Flylow 72]

After 1 hour drive to purchase multi-meter, completed test findings are as follows.
Key on vehicle off - .5 volts
Full open throttle- 3.5 volts
The needle moved up and down smoothly several times.
Top wire 1 vc registered a constant 5 volts

 

[Parsnip]

Well the 3.5 volts is in range in the FSM which calls for 3.2 to 4.6 at WOT. So rule out the TPS for now.

I would rule out a vacuum leak because that would tend to affect idle more than driving with partial throttle open.

That means you are losing spark or fuel.

Fuel would be tested best by attaching a mechanical fuel pressure gauge and taping it to the windshield so you could see it as you drive.

You can do some tests on the fuel pump circuit, however.

The ignition system has numerous checks that can be made with your multi-meter.

Private message me an email address that I can send a 50MB PDF file to and it will outline all the tests you can make with your multi-meter.

ETA I should also mention a stuck EGR valve that sticks open but I think that is far down on the list of suspects.

 

[ppc]

If you disconneted the battery when replacing the starter then there is a good chance the fusible links may be the isuue. Start with the simple things and the things you most recently messed with.

 

[Flylow 72]

If you disconneted the battery when replacing the starter then there is a good chance the fusible links may be the isuue. Start with the simple things and the things you most recently messed with.

Can you clarify "fusible links".

 

[jonheld]

Can you clarify "fusible links".

We discussed this on Wednesday. 3 wires coming off the positive battery terminal. 2 go to a black junction box and 1 to a small grey connector. Known to get intermittent over time.

I would also like you to clear any old codes in the ECU by removing the 15 amp EFI fuse for about 10 minutes. Reinstall the fuse after that time and try to recreate the problem. If/when it reoccurs, read the codes according to the FSM.

Engine NOT running. Key OFF. Jump pins 3-6. Turn key ON. CEL will blink a series of codes.

I attached the EFI codes pdf below.

 

[Flylow 72]

Again, excuse my ignorance. Could you clarify "jump pins 3 through 6".

 

[Parsnip]

he means take a paper clip and bend it into a U shape and put one end in pin 3 and the other in pin 6

 

[Flylow 72]

Where are the pins?

 

[Flylow 72]

Also, looked at fusible links coming off positive battery terminal. Not sure what to look for or how to test.

 

[LS1FJ40]

On the firewall in the engine compartment. On the passenger side. It's about 1.5"X1.5" box.


Sent from my iPhone

 

[Flylow 72]

Found it, thank you.

 

[Flylow 72]

Cleared codes, now cannot recreate problem. Ready to pull my hair out. With regard to fusible links I'm guessing I should just replace the black junction box and the small grey connector.