p0171 system too lean bank 1

[tyler]

So I ended up changing my ECT sensor on my trailblazer 06, which was a complete pain in my ***! Temperature gauge on my dash is finally reading accurately, but the code is still up so i think the thermostat might be gone as well? I don't know I don't want to get into it now because I have a bigger problem. Hopefully I'm posting in the right forum!

So I'm running a code p0171 "system too lean bank 1." Does that mean I'm getting to much oxygen or not enough, or to much or not enough fuel in the engine? This is a '06 trailblazer that I bought about 6 months back. A lot of problems that I've been having to fix. Vehicle came from Maine, which is rough terrain up there and cold winters, and I bet whoever had the vehicle probably beat on it a little and took it off roading. It has about 126xxx miles on it! I've already fixed so many codes, and problems I lost count! I think its because its a old vehicle with a lot of miles and it came from the state of Maine..bad winters..

The tb is surging when I start it up, almost sounds like its going to stall about every 2 or 3 seconds, and then picks right back up. When I'm driving, it performs horrible, horrible acceleration. I cant really notice the surge when i'm driving , but i can hear it when the car is idling. I also have an exhaust leak, I don't know if that's triggering the code, but i doubt it because exhaust leaks are emissions. I think the leak is in the manifold gaskets. That's for another day though. I know this p0171 code is "broad" and can mean many things, it's hard to track it down, so I was seeing if someone could help or give me some advice from the information I have provided.

Thanks!

 

[Sparky]

On the thermostat - when warmed up what does the gauge read now? It should be pointed straight up at 210.

System too lean means it is getting either too much air or not enough fuel. Many times it is caused by a vacuum leak of some sort, or an issue with the airflow sensor not reading the air volume correctly. Try cleaning your mass airflow sensor (use only that sensor cleaner, don't use carb cleaner!). If that doesn't help, also listen for any whistling when the engine is running - a whistle can be where air is getting sucked in. You can carefully spray carb cleaner in small bursts around places like the intake etc and listen for changes in the engine sound as you do so. Carb cleaner is flammable so small amounts will burn in the engine OK, but don't go hosing down your exhaust or electrical stuff with it as that may be a fire hazard

I've heard of a bad exhaust leak causing a lean code because fresh air can get into the exhaust system and throws off the O2 sensor reading if it is upstream of the O2 sensor.

 

[gmcman]

Check the big vacuum hose under the intake resonator, make sure it's connected. Check the molded hose between the #3 & #4 intake runner, ensure it's not loose.

 

[djthumper]

How long have you had it? What other maintenance have you done to it? If you have not cleaned the throttle body I would definitely look at that. I would also take a look at your MAF that could give you the reading if it is dirty and it doesn't get enough airflow past it. What other codes were you receiving? that can help us fill in the gaps.

Does this happen all of the time or after a cold start?

 

[tyler]

On the thermostat - when warmed up what does the gauge read now? It should be pointed straight up at 210.

No the gauge is below the 210 mark, always. I'm going to try you guys advice when I have time, sometime today hopefully.

How long have you had it? What other maintenance have you done to it? What other codes were you receiving? that can help us fill in the gaps.

Does this happen all of the time or after a cold start?

The only other code that shows up in the computer is P0128 Coolant thermostat (coolant temperature below thermostat regulating temperature.) I already changed the ECT sensor due to this code, maybe I need to change the thermostat next? I've done other maintenance to the vehicle as well. I had the vehicle for about 5 months now. The dealer purchased it from an auction. The surging of the vehicle happens all the time will the vehicle is running, cant really notice is when moving, but when idling or in park you can hear it. Sounds like a lawn mower running out of fuel. every three seconds or so, it sounds like it's going to die but quickly picks back up. Trying to get the TB in tip-top shape before winter arrives..

 

[Mooseman]

You need to clean the throttle body as per the how-to on here somewhere. Disconnect the battery while doing it.

 

[tyler]

Easy job, I'm definitely going to do this tomorrow when I get out of work. Hopefully this is the cause for the code, and poor performance. I believe it might be, don't know if the previous owner cleaned it. I doubt it. Curious on how dirty it is.
I'll get back to you guys.

Thanks!

 

[djthumper]

Definitely need to replace the thermostat.

 

[Sparky]

Yep, stat is dead.

 

[tyler]

So I cleaned out the throttle body, runs a little better i guess, but still sounds horrible when idling.. Doing thermostat next week.
When I was changing the ect sensor, I might have knocked off a hose at the bottom back engine where the ect sensor is near. There's like these two rubber hoses connecting to a triangle white plastic piece, that has a hose going to the bottom almost near the ground, but I can't get a good look on the bottom, not even sure where it leads to, but I think I knocked it off wherever it goes, not even sure what it's for, might be a vacuum line? If someone could enlighten me that would be great so I can do some research and see how to get to it.. I might have to put it on a lift.

Also the trailblazer burns a lot of fuel. Not sure why either, runs like crap and I'm still getting those three codes.. Also getting a new gas cap next week as well as the thermostat..

Any idea what the hose is, and where it leads to?

EDIT : I think it might be the heater hose? No relation to a loose vacuum hose?

Thanks guys!

 

[Mooseman]

Replace your stat ASAP. You're killing your cat and will get worse with that extra fuel.

We would need a pic or something to be able to identify the hose.

 

[tyler]

Cat as in catalytic converter?

 

[Sparky]

Yep. With a bad stat, it will be burning extra fuel trying to warm itself up, which kills your mpg and eventually can clog up your catalytic converter. No fun.

 

[djthumper]

from what I hear a clog cat on these things can be quite the bear to get off.

 

[tyler]

Changed the stat today, wasn't as bad as the ect sensor but still a nightmare (just a little.) the car isn't surging as often or as much, engine is even quiter, I'm surprised. My evap leak code is from my gas cap I believe. I'll replace that tommorow. No codes since I had the battery disconnected for quite some time. Went to my buddies shop to use his computer, and no pending or stored codes so far.
Do you think it's possible the stat will solve my p0171 system to lean bank 1 code or no?

Edit: the reason I say the evap code is from the cap is because I changed both evap valves the one in the front and back. I think ones called purge valve and the other is called something else.

Thanks guys for the help!

 

[Mooseman]

I think it will come back as I have never seen that with a stat change.

 

[tyler]

I think it will come back as I have never seen that with a stat change.

My theory is that because the stat was always open the engine was to cool all the time. Theorfore the computer was telling the engine to burn more fuel causing the air/fuel code p0171 too lean bank 1.

EDIT: even though the p0171 means to much air or to little fuel.

I'm probably completely wrong though. Just a guess and a hope lol

 

[tyler]

100 + miles still no stored or pending codes. TB still surging, now its only bad when its a cold start, and barely does it all when at operating temps. Also my coolant temp is a hair above 210, is that a problem? Is there an article or a thread somewhere that can show me how to find an exhaust leak? I'm having trouble narrowing down to the right thread that would show me. I think it could be the manifold and gaskets.. heat sometimes comes out from under the floor ducts. sometimes get a vibration in the gas pedal. I drive with my windows down last thing I need is to pass out from carbon monoxide lol

 

[Mooseman]

Popped/broken manifold to head bolts are common. Earlier years had cracking manifolds but not sure about later years.

 

[Sparky]

If your windows are down you won't pass out from CO.

 

[tyler]

If your windows are down you won't pass out from CO.

Ik that's why I keep them down if I'm driving and I think I'm feeling light headed lol someone told me to put a rag in the tail pipe and put it on a lift and listen for hissing, where the leak is coming from.

 

[tyler]

P0171 system too lean bank 1 issue solved. My air filter housing box wasn't on tight enough. Evap leak next, but that's simple.