P0172 2000 Toyota Sienna

Newbie with the questions. 244 000km on this Toyota
i have owned this Sienna for 11 trouble free years then came the P0172 :Initially no codes set but lost power up a hill like the transmission was done :After a restart drove ok then eventually became undriveable : Parts cannon started with a new MAF but no change : went to a mechanic and they told me it was an 02 sensor (not AF sensor so that may still be an issue )Bank one / that did not fix it as the code came back
they said it was an injector on bank 1 : I ordered 6 refurbished Denso’s and they changed the plugs , wires , fuel filter and PCV. This did not fix it and they gave up / I bought a scan tool to try and sort this out myself now 
I pulled one of the plugs on bank 2 and it was dark like it was running rich : the exhaust smells rich have a known good MaF / cleaned the IAC and the throttle body / vacuum is around 18 on the gauge 
i am about to test for the fuel pressure as it did not look like the mechanic did : the fuel pressure regulator is with the fuel pump in the tank and I believe this is a returnless system with the excess fuel staying in the tank ?
if the fuel gauge shows normal pressure, where else should I look?
Thanks , Rick (Vancouver BC

 
   

 

Holy negative fuel trims in that Freeze Frame.   Given how both banks are equally negative, I think it's safe to say there's something impacting both banks.

Fuel pressure is a suspect, but kinda difficult to check on this engine due to the lack of a test port. The fuel pressure would also have to be extremely high to account for trims this negative. I'd suggest checking some easier suspects first.

I know you replaced the MAF, but I'd still suggest checking its readings anyway. At hot idle with no loads on, we generally expect the MAF rate in g/s to equal engine displacement. In this case, 3.0 g/s.

I'd also suggest watching the O2 signal and trims while the engine is warming up from a cold start. I see you've got a capture from an Autel, but again, I'd suggest doing your own oxygen sensor testing. With the engine at a hot idle, create a large vacuum leak and make sure all three O2 respond quickly. Add brake cleaner to the same vacuum leak and look again.

Thanks Tyler, I will try your suggestions hear you on the MAF and I ended up swapping it multiple times with a used OEM as well but still the same . Thanks for providing reference number for that as well ,

Fuel tested at 50 psi which seems to be normal although I see it posted as 35-45 on some sites
MAF is between 5-8 on startup then settles down to between 3 and 4
O2/AF sensors don’t seem to react to rich conditions or lean when I tried they stayed maxed out in the .95 .97 range
I wonder now if all the injectors I replaced are bad : I did not see the data when it first happend to know if both banks were rich or just one when they said to change an injector on bank 1
I pulled and cleaned the bank 2 a/f and it looked ok better than the spark plugs that are black :
The only way I get negative on the voltage /o2 sensor is right after I blip the throttle and the engine gets more air
Bank 2 sensor 1 still moves slow but in the same direction as the other 2

your iat temp looks low , also might want to check evap purge not staying opean. good luck

The initial code reffered to bank 2 while the fuel trims are negative for both banks.

Are you positive the injectors are the correct ones or may they have a different flow rate?

Thanks for the response
That’s a great question and I was told the injectors were correct but didn’t it test them to verify nor did the mechanic
I will have to go back to that as my last resort : I have the old fuel injectors and would rebuild those before putting them back in

The evap purge seems to be operating correctly: I have identified an out of range throttle position sensor and will change that when the part arrives to see if I get it resolved
My temps are in Celsius so that may be confusing

No success yet
Throttle position sensor was replaced and the range is slightly better but not what i had expected
It’s max is now 52% better than in the 40’s but no where near the 72% that I believe it should be
I created a vacuum leak after the MAf and no change in short term trims they stayed -20 but the idle increased tried a Vacuum leak before the MAF and the same results stayed at -20 : the only way they go positive is after pressing the accelerator quickly am looking to get my old injectors rebuilt/ tested and last resort is changing them

 

Would this be a cause or a result of running rich?
Does the ECM keep the IAC at this position or is it the other way around : at idle 
Thanks  ,
Rick 

Solved : fake Denso + wrong injectors from EBay :(I am passed the return window and the seller won’t warranty his lifetime warranty on these )I tested and rebuilt my original injectors thanks to YouTube and getting the original workshop manual : I don’t know if I solved the original problem along the way but fuel trims are back in low single digits

Good news, thanks for posting a follow up with the fix

Noah wrote:

Good news, thanks for posting a follow up with the fix



​​+1