Help. 2006 Scion xB RS 4.0 1.5L automatic 179k miles gas smell P0172 system too lean Bank 1 comes up on scanner as pending so you go about 60 miles before the light will come out saying P0133 O2 circuit slow response Bank 1 sensor 1 its had all injectors replaced 1 coil cause the previous owner said it had Cylinder 4 misfire and then all this starting happening he's done cat back OEM reg exhaust cat seems fine so ready live data I don't know how to read but a mechanic said its all reading right for most part. So here's the deal starts fine revs up down no issue idle is OK and its only every other time you go to take off and it like hesitates for a sec and then its good to go drives normal full power. I tried 2 O2 sensors in Bank 1 yet still throws the code slow response tried MAF and no difference so put old one on cleaned it with computer duster temp sensor plugs B12 Chemtool in the intake and in the tank and checked for vacuum leaks all looks good tried spraying starting fluid around intake and no difference to see if it was leaking I don't have much money left so I have put on a spark plug fouler for now and had that all put on just to try and get it to pass NYS inspection. I smell it running rich and just 50 miles on a new O2 sensor and its pure black must be from running rich. Help please.

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Sounds like a thorough examination. P0172 is actually system too rich.

Since you didn't mention it, did you get a chance to check the air filter?

Here's a pretty good set of instructions to check and or test your oxygen sensor and air fuel ratio sensor. It's not vehicle specific but the theory is easy to comprehend.
https://repairpal.com/obd-ii-code-p0133

 

 

Yes, tried that too. I just can't catch a break. I'm thinking maybe the injectors the guy put in were wrong but don't know how many Psi it should be running at the fuel pressure.

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I struggled with P0171 which is System Too Lean. I changed injectors, fuel pump, intake gasket, and checked for vacuum leaks. Nothing worked. I bought new MAF sensor and that didn't work either.
I ended up cleaning my old MAF sensor and reinstalling and that finally did the trick. By the end of it all I thoroughly cleaned the MAF sensor twice. Just my experience but perhaps our sensors are temperamental.

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If the injectors are suspect, consider asking the guy which injectors he installed. If you can get a part number, Google it for compatibility with your specific car. I'm not saying the guy's suspect however everybody makes mistakes.

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You need to scan and post what the long term fuel trim is at (for idle and 2000RPM if possible) P0172 is triggered around +20%

Too rich fuel-to-air ratio. Your oxygen sensor is reporting this and you can smell gas so there is no arguing with the computer on this point. Possible reasons for this:

• There is a leak in the fuel line before reaching injectors, system requests more and more because it's seeing too much oxygen in the exhaust. You can smell it because it's leaking. Is there any trace of gas on the ground when you park somewhere?
• fuel is not being burned in one or more cylinders and the system is requesting more and more, so much so that you can smell it. Check spark and timing
• There is a leak in the exhaust before the O2 sensor. The system can't measure correctly, and requests more and more fuel. You can usually hear these so that seems unlikely.
• Too much air getting into the system or an incorrect measurement on the air passing the MAF. Clean the MAF and Throttle body. Check for vacuum leaks.

 

OP, did you ever get this sorted out? I am having a real similar issue and really struggling to get it straight. P0172, System too rich. Car bogs, stutters when attempting to accelerate from a stop. But it's seemingly random, sometimes it'll take off just fine. I've checked the air filter, changes plugs, cleaned the MAF & changed injectors.

 

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Have you figured this out? I am having the exact same problem.

 

Hey all, I got a tip that worked awesome. seems the TCS gets stuck in a weird loop, turn it off for a few miles. mine turned back on again when I restarted the car no problems since. About 2000 miles still running great.

 

I have 2 xbs with p0172 and it keeps bugging when I try to accelerate. Driving me nuts

 

What have you tried?
Do you have a stock system?

 

Everything is stock.

new plugs, coils, injectors, vvt solenoid, cleaned vvt filter underneath the solenoid, new crank sensor, new cam sensor, new coolant temp sensor, new 02 sensors, new maf, new evap, new air filter Im going crazyyy

 

Sounds like you've tried just about everything. The only other thing I can suggest is checking the electrical connectors for corrosion and tightness. Specially at the MAF and O2 sensors
For "Tightness" this is the kind of thing I mean

 

Careful there. Looks like you have the Parts Cannon firing left and right.

My first area of caution is what kind of parts you're installing. Are they OEM or aftermarket? On some parts (tires for instance), there is very little difference. On others (coil packs for instance), there are huge differences. In fact, I've rarely seen an aftermarket coil pack work for more than a short period of time. Some even fail right out of the box. OEM on the other hand are generally good for more than 100,000 miles. Get my drift here?

Second - and related to the above - you may have replaced a perfectly good OEM part with a defective aftermarket part. Unfortunately, you've thrown so many parts at it that this will be difficult to determine.

The big lesson here? Don't just throw parts at a problem. Test to determine what you really need and replace with OEM parts for the best results.