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I just bought a 99 4runner limited 4wd with the 6 cylinder motor. I bought it knowing it had a CEL and a coolant leak. I replaced the water pump and that fixed the coolant leak but now I'm trying to track down this CEL. The code is p0172 (bank 1 rich) and I have already tried diagnosing a lot of things.
I checked all real time sensor outputs and it looks like my long term fuel trim is incredibly negative. The only other thing that may seem a little concerning is the maf output is a little high ( 3.3-4.7 g/s ).
Anyways, I started with the basics. I replaced the plugs, wires, and coils. This helped but didn't fix it. Then I cleaned the MAF sensor and replace the bank 1 sensor 1 o2 sensor. This also helped but didn't fix the CEL. I then removed all the fuel injectors and cleaned them - they all seemed to spray pretty well and held pressure without any leaks (not sure if this did anything).
After doing all this, the CEL still comes on with high negative long term fuel trims. The strangest thing is that it only runs rough at idle. As soon as I start driving and putting the engine under load, it seems fine. The CEL is only ever triggered at idle. The other thing to note is that acceleration is smooth and powerful and gas mileage isn't very good at all.
I pulled the injectors and sprayed carb/throttle body cleaner through them all. They all held pressure without leaks (this was no official test and the pressure was only momentary).
I pulled the injectors and sprayed carb/throttle body cleaner through them all. They all held pressure without leaks (this was no official test and the pressure was only momentary).
Just how much pressure does spraying from a spray can give you.??
I just bought a 99 4runner limited 4wd with the 6 cylinder motor. I bought it knowing it had a CEL and a coolant leak. I replaced the water pump and that fixed the coolant leak but now I'm trying to track down this CEL. The code is p0172 (bank 1 rich) and I have already tried diagnosing a lot of things.
I checked all real time sensor outputs and it looks like my long term fuel trim is incredibly negative. The only other thing that may seem a little concerning is the maf output is a little high ( 3.3-4.7 g/s ).
Anyways, I started with the basics. I replaced the plugs, wires, and coils. This helped but didn't fix it. Then I cleaned the MAF sensor and replace the bank 1 sensor 1 o2 sensor. This also helped but didn't fix the CEL. I then removed all the fuel injectors and cleaned them - they all seemed to spray pretty well and held pressure without any leaks (not sure if this did anything).
After doing all this, the CEL still comes on with high negative long term fuel trims. The strangest thing is that it only runs rough at idle. As soon as I start driving and putting the engine under load, it seems fine. The CEL is only ever triggered at idle. The other thing to note is that acceleration is smooth and powerful and gas mileage isn't very good at all.
Anybody have any insights?
Hello I am having a very similar issue with all of the same symptoms on my 1998 3.4l T-100, I was wondering if this issue was ever resolved? If so, please let me know so I can try to get my rig back on the road. Thank you!
08-18-2021, 11:18 AM
