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Dj, ASE Certified Technician
Category: Toyota
Satisfied Customers: 1910
Experience:  ASE Master Tech, 30+ years in automotive repair.
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I have a 1989 Toyota Tacoma 5-speed V6, with 145,000 miles,

Customer Question

I have a 1989 Toyota Tacoma 5-speed V6, with 145,000 miles, and I am have a problem with the fuel system. While driving the truck, it got to where it would start cutting out at more than half throttle. Then, it completely quit. I replaced the fuel tank fuel pump, fuel filter, and fuel pressure regulator, and it started running again, but only to the point it was at before totally quitting, which is cutting in and out at more than half throttle. At half throttle it runs just fine. There are no check engine lights on. Any thoughts?
Submitted: 2 years ago.
Category: Toyota
Expert:  Dj replied 2 years ago.
Hello and thank you for trusting us with your question. I'm DJ.
The first thing I would like to try is bypassing the air flow meter, throttle body and circuit opening relay.
We can do this by putting a jumper between B+ and FP in the DIAGNOSIS connector next to the fuse box under the hood.
Under the lid is a chart that shows what each of the pins is. We need to jumper B+ to FP which will supply ignition voltage to the fuel pump. I just use a paper clip bent into a U shape and stick the legs of the U into the terminals. They are shaped like this: O_O and the paper clip fits right into one of the O's.
Try this and let me know if the engine stays running throughout the range.
Customer: replied 2 years ago.
No, still the same results. Thanks though.
Expert:  Dj replied 2 years ago.
That was just the first test. Don't give up yet.
OK, let's leave the jumper in place for the next tests.
Have you got a volt ohm meter? We'll need one to test the TPS and the air flow meter. Doesn't have to be an expensive one. Under ten bucks will get the job done. I've got a couple of the Harbor Freight ones and they work great.
If the point where the cutout happens in always at the same throttle point, then I would start by looking at the TPS output first.
The ECU turns on the injectors for a specific amount of time depending on the input it see from the distributor, air flow meter, throttle position sensor and the engine coolant temp sensor.
So if one of those sensors isn't giving the correct signal to the ECU, the ECU won't deliver the right amount of fuel to the engine.
This is the best information I've found for testing a TPS.