2007 TRD P0171 lean code

Bad spark plugs and/or wires, an exhaust leak or bad air/fuel sensor can also throw this code. I fought this code for awhile on my 04 and it turned out to be a hidden vacuum leak.

 

How about updating your information. There may be someone near you that can help. Only so much can be said over a forum. We can tell you what to look for until we are blue in the face. I know there are a handful of smart guys on here.
That, or man up and take it to a shop where guys that work on them every day would know where to look. Just my two cents.

 

Here's what I found. Under load traveling up a small hill.
Cal. Load % = 90
MAF = 5.2
Fuel trims
S1=20
L1=39
S2=23
L2=39

At warm idle I get
Cal load% =27
MAF = 0.5
Fuel trims
S1= -5
L1= 30
S2= -7
L2= 31

The only codes I get are 171 & 174 (lean on both banks). Once it starts not wanting to respond to throttle & engine starts stumbling it will not stop until it finally shuts off. Then it will fire right back up & run better for a small time. But if you shut the key off when it has started these symptoms & before it shuts down by itself, then it is very difficult to crank. I also noticed that after this has happened & u restart truck short term trim is like -17 and long term is +39. Way out of spec.

 

Try unplugging the 02 sensors and just drive around like that.. I wonder if one of them is shorted out and sending a weird signal to the computer

The calculated load at 90 going up hill means that the pcm is recognizing your request for power. That's a good sign for the maf..

It looks like your trims (long term) are hi at idle and under load. The pcm is begging for more fuel. (If unplugging the 02 sensors doesn't help) it looks like all the sensors are recognizing a need for fuel!

Fuel pressure and fuel quality are highly suspect. That sucking sound is likely the engine "gasping" for fuel.. I know the sound you're talking about.. I trust that you looked really hard for a vacuum leak. But actually, if you had a vacuum leak the the trims would stabilize once the throttle is cracked open. Just the fact that the trims are hi all the time makes me think about a constant lack of fuel..

 

@b_r_o thanks. You just put the fuel trim's in perspective for me.

@Derrickm72 do you have a fuel pressure gauge? You stated earlier that you disconnected the fuel line near the tank and let some out... Did you use the fuel pump or a siphon? I would imagine that if you used the fuel pump, it would send gas flying out of the hose. I don't know what the fuel pressure is supposed to be, but I would guess that it is up there.

 

• yea, your trims are way out there. Since they are still similar on both banks it's not going to be an exhaust leak. How many miles on your truck and what kind of fuel do you put in? I'm gearing towards a fuel pump issue. Thats why its starving equally on both banks. If it was a plug, coil, anything like that it would be uneven. Because you are an 07 with probally some good miles if it was me I would immediatly put in a new PCV valve. Cheap and 5 minutes to replace. If it's clogged it could cause these issues. That or your fuel pump.

 

Gen' 2's have an intank fuel pump with a filter screen. It starts to clog after 30k miles and slowly starts to run lean. There is a reason why you gen 1' guys have 200-200k miles on your trucks and you dont see that with future gens. You have replaceable fuel filters. I threw a URD fuel pump kit with an in line filter and I change it out every 30k miles. If I dont the truck start to have a hard time cranking over.

 

I don't currently have a fuel pressure gauge. Yes, I let fuel pump itself pump out a gallon, it did it fairly fast too.

 

Yeah only the short term trims ever get low or negative even. And that's always around start up or after the issue occurs & I refire motor.

 

I would do the pcv valve and have your fuel pressure checked. I'm sure that your fuel pump is going out and if its not, than the filter that is in the tank unit with the pump is clogged up. Your short trims are in the " -" on startup because the truck is trying to dump fuel to richen out the mixture. But when you start driving it's just starving for fuel. I'd get it sorted asap. You will destroy your engine. Toyota codes trigger when you are already on the threshold of S.O.L

 

Get your hands on a fuel pressure gauge, duct tape it to the windshield and start driving! Personally I would not spend any more money on parts until I know the fuel pressure is good

 

Fuel pressure i think in the normal range is around 50-55psi / correct me if i'm wrong.

I did forget to mention though that it is more likely that your Fuel Pressure Regulator is taking a crap before the fuel pump itself.

 

buddy of mine had an issue with his car, it ran fine for a bit but once it warmed up half the engine would stall. ended up being a clogged cat lol

 

Any1 recommend a decent priced fuel pressure kit that would have proper connections?

 

Cat converters operating inefficiently usually throw a P0420 code...I've had to deal with that expensive disaster too lol.

 

Yea but if your buddy watched trims for both banks hes see only the bank with a bad cat was running lean. Its not impossible that both cats are shot in which case it would be a devil to track down.

 

I had the p0420 also. Got a dt-y pipe with some new rear 02's and i was golden.

 

fair enough, I kinda figured it would of thrown a diff code but wasn't sure haha just trying to think outside the box hahaha

yeah this was on a crossfire not a taco, I don't even think it was throwing codes to be honest but I really don't remember cuz it was a while ago lol he bought it for a good price, really good price haha but it had been in a front end collision but all repairs were done. picked it up and on its way to its new home it stalled, spent a while in the driveway parts charging with some mechanic buddies. finally took it to a shop, put it up on the lift and the cat was bent restricting flow and after running for a while it would stall half the engine lol replaced the cat and all was good hahaha but I doubt that both cats are blocked, and like mentioned above it would throw a diff code then OP is getting.

 

Also with my ultragauge it was showing my cat code under "pending" as it was right near the threshold of triggering a cel. Which it did for one day and went back. I knew something was off because my drivers side bank fuel trims were off wack.

 

hmm I wonder if they might be related then. P0420 doesn't always mean a bad cat, it can also be triggered by an exhaust leak...which can also trigger a P0171. Something to consider anyhow