P0170 Fuel Trim Bank 1 (Solution)

What's up guys!

Relevant Truck info:
1995 Tacoma 3RZ 4X4 5speed.
No Cat. URD O2 sensor emulator, EGR bypassed.

I ran in to an issue this past Monday and I wanted to share my solution for anyone who may experience these symptoms.

Problem:

I was driving home from the mountains and I noticed a lack of power. I could not put more than perhaps 1/2 throttle down before it tried to faceplant. Had major hesitation after 2K RPM. I nursed the truck home and did a diagnosis.

The truck had a rough idle although still at 7-800 rpm, sputtering when given throttle and miss-fire. Also, it would backfire in to the intake when I played with it. Did not want to go past 2K rpm although if you gently gave it throttle it would work it's way up very slowly. Not able to be driven.

The code that popped up was P0170 Fuel Trim Bank 1. At first, I cleaned the MAF, swapped out the Fuel Pressure Regulator (one I already had), checked for vacuum leaks with some brake cleaner, and looked at the live data from my scanner.

The TPS was at 10% (within margin)
The Short Term Fuel trim was over 30% <---not good
The MAF was within FSM spec at idle

I went ahead and tried to give it some throttle again while I sprayed a bit of brake cleaner in the intake at idle. It Revved up perfectly! This told me it's a lack of fuel as I did not have a Fuel Pressure Tester handy.

I have replaced the Fuel Pump about a year ago. The original one completely died after I stopped for 15 minutes. This one created a low pressure situation. Aftermarket parts for you.

Solution:

Replaced the fuel pump. Fixed all issues, code gone, truck feels alive.

Thanks for your patience on this long winded story. Just wanted to share for anyone who has this issue. Essentially, if you have these symptoms it's either your MAF (clean it and see what happens), but most likely your fuel pump is on it's way out.

 

Same story that happened to me I was just gonna change fuel pump anfd now I feel certain it’s the problem

 

Easiest way is to take the bed mount bolts out except for the ones in the rear. Just loosen those. You should be able to lift the bed up by the cab and use the rear bolts as a hinge. I put some 2x4s under the bed and rail and was able to swap the pump on the tank. Took 30 min. Don't forget to disconnect important stuff like filler neck any wiring etc.

 

Don't rule out a clogged fuel filter... I had a similar issue on my 4 cyl but the symptoms were limited to not being able to get it above 2500 RPM and an inability to step on the gas other than VERY lightly. Pressing hard on the gas pedal resulted in the engine almost stalling every time. Could not gain any speed climbing the mildest inclines (even going on an overpass). Got the truck home, replaced the fuel filter and all was well again. The filter was clogged such that any sudden demand for fuel caused the obstruction to clog up the filter. A gradual demand left the clog such that it would not totally obstruct the "out" tube.

 

1995 Tacoma 2.7 4cyl 4x4 249k miles

Cleaned the M.A.F. this weekend, and ran the truck a short distance 5-8 miles. No issues.

P0170 Code appeared this colder morning at start.
Drove to work, 14miles at various speeds with no with no issues or symptoms. Gas is new and has not sat long.

I have attached the freeze from data from my cheap scanner.

I am thinking that its fuel related? Any ideas? Check fuel pressure? Change fuel filter?

 

Replacing the fuel filter, especially if it's been in there for a while, is a no brainer to help narrow down the diagnosis.

 

So just wanted to do a follow up and let you guys know that it was in fact the line that connected to the fuel pump that came undone and caused the truck to throw p0170 code

 

I’m struggling with this code right now. 95 Tacoma 3.4. I changed out the fuel injectors, valve cover gaskets, fuel filter, throttle body gasket, cleaned out the throttle body, cleaned my MAF, changed the downstream O2 sensor, and the code p0170 popped up. Erased it comes back every 5-10 miles. Yesterday I drove home from work and the code p130 and p133 appeared. Issues with the upstream O2 sensor I suppose but I’m definitely not convinced... I ordered a Denso and I’ll be replacing it tomorrow. The truck runs fine but the code pops up on the regular. I probably have a vacuum leak.