p0170 fuel trim bank 1 malfunction

[state]

I have been fighting this CEL for 2 months now. I have replaced both o2 sensors. No help. Here's the latest. I got some info from alldatapro.com that said for a p0170 on my 95 Legacy Wagon to first check exhaust for leaks. No problem found. Then the air intake for leaks. No problem found. Then fuel pressure. I don't have a gauge so I skipped that one for now. Now to what I did find. The engine coolant temp sensor. My Haynes book says to test the resistance across the terminals with the engine cold and then when hot. The readings I got were within the range listed. So far so good. Then I am to check the reference voltage to the sensor from the ECU. It should be 5 volts. It said to disconnect the connector to the sensor and with the ignition on and the engine not running I should see 5 volts. I get 145mv. I'm sure I was making good contact. Could this be my problem? There are only 2 contacts in the connector. Could my ECU not be sending the 5 volts or could I have a bad wire between them? Car doesn't run bad. CEL just keeps coming back.

[eamiller]

you didn't indicate mileage, so I assume you have a fair bit. It could be that 1 or more injectors are clogged, or poorly performing (in addition to a fuel pressure problem). There is more than a little research that has been done showing that certain brands of gasoline don't contain enough additives to effectively keep the injectors clean over time. Also, when was the last time you changed the fuel filter?

 

BTW, RedLine makes a fuel additive which works great (and has been tested).

[state]

I only have 80000 miles on it. I had the injectors cleaned about a year ago. I changed the fuel filter about a month ago. I now occasionally run some amsoil fuel injector cleaner.