Tackling P0171

This winter I has the bank 2 rear 02 sensor flange give out and the sensor was flopping around. I drove it probably 2000 miles like that and the check engine light on, p0151 or 0152 code, it sometimes would start hard, with a rough idle at first but drive fine. Truck was idling the other day while loading a trailer and started kinda popping with a rough idle. Now 2 codes come up, with the 0171 being the other, lean bank 1. I fixed the flange and installed a new 02 sensor but now the lean bank 1 code won't go and the truck idles real rough at times with lots of hesitation until road speed is achieved. Pops at hard acceleration. new pcv valve and sprayed starting fluid all around but no noticeable leaks. Fuel filter is next

 

You most likely have an air leak, check for leaks with soapy water

 

Checked with soap, carb cleaner and starting fluid, came up with nothing. Unhooking most hoses does nothing, pcv hose removal causes serious idle issues and 1 other, but it no indication of leaks. It’s only reading lean on 1 side but I had a new maf sensor and put that in, no change. I don’t think it would be a fuel filter issue

 

The rear o2 sensor only checks the condition of the catalytic converters and doesn't effect the way the truck runs. You should probably knock out the front 2 sensors as well and only with denso parts if they haven't been done at any recent point.

 

Check fuel pressure? If it's the original pump it could be on the way out.

 

Ordered 2 new denso sensors should be here tomorrow. Would bad o2 sensors cause these rough conditions?
Wouldn’t fuel delivery issue cause misfires? The condition is only throwing code on 1 side.

 

Replaced o2 sensor bank 1, no change. Ordered off Amazon, got 1 Correct and 1 incorrect sent.

 

IMHO, our O2 sensors, along with other engine parts should only be OEM from reputable places, not from fleabay nor Amacon. Personally, I will only buy plugs, coils, A/F-O2 sensors and certain other engine items from an online Toyota dealer. P0171 can be a crap shoot, vacuum leak, exhaust leak, injector leak....etc. Our ECU is very picky when it comes to fnt/rear sensors and knockoffs are common from cheapy places.

 

Bank1 Sensor 1 right? Yeah Scamazon is known for fake parts these days. Though I haven't run into any that I know of but I've been trying to stick to rockauto only for car parts.

 

Yes

 

Progress…if you call it that
Checked the timing, looks ok
I unplugged the battery for a little bit while popping the timing covers, now the truck barely runs, I drove it down the road and to my driveway to work on it because it still has hesitation and popping but now I can barely get it to start and stalls when I try to give it gas.

 

I seem to remember a similar post six months ago. Guy's truck seemed to deteriorate from running fine to practically dead within a few days. I think it turned out to be a crank position sensor, even though no cps was being thrown. I would think fuel related issue would be worth investigating as well.

 

Let it sit a while, runs again, drove it. idles good sometimes but still has massive hesitation and almost stalling and popping when I step on it. To me I feel like if I step on it hard enough it should cough something up and come out of it but those were the old days.

 

Should there be a reading on the bank 1 o2 sensor? Maybe I did get an Amazon denso rip-off

 

Few things I notice….
1 OBD2 Stat CA….means closed loop, a good thing

2 LT FUEL trims….ECM sees lean condition and it adds fuel….21.9 is not a good thing, having to add way to much

3 MAF of .99 is way too high….bad maf, dirty maf or maf connection issue….MAF can also be your P0171 issue

Will that Actron show IAT(intake air temp) ?
Reason being the IAT is inside of MAF and if there are issues with MAF, might show up according to what IAT says. How good is your air filter and there are no squirrels nests

Bottom line IMHO, you need to see why you’re having to add so much fuel….fuel pressure, fuel filter, injectors….etc

Your O2 sensors are after all that and yes OEM O2 sensors are best purchased from dealer or reputable place like Rockauto

no home internet so having to type on phone and that sucks

 

I checked for a misfire by unplugging injectors, then coils they all caused slight disturbance. Threw a bunch of codes doing that, cleared them and now running rougher than this am.
while driving earlier my bank 1 and 2 o2 sensors were close to matching readings so I think they are good.
Loop is open now

 

What are the four O2 readings while running? Upstream should be switching between 0.1ish and 0.9ish volts, downstream should be steady around 0.4ish volts

 

Those readings are with the truck running, I was getting better readings when I took it for a drive earlier,

 

I’m getting ready to buy a new truck

 

Were you ever getting readings similar to what I posted, or is it always constant 0 volts on three sensors and 0.1ish on the fourth sensor?

No exhaust leaks right?

 

earlier when I was driving the pre cats would go from 0 and climb would both be fairly even climb higher and drop at around the same rate. I never knew this reader could see these things, just used it for codes so I don't really know what I'm looking at.
I do have exhaust leaks beyond the cats at the connections. This morning I almost thought it was gonna come out of its funk but now its worse again.
I'm probably gonna have to do new headers, and cats.

 

Cats are bad when the upstream and downstream readings are similar. If upstream are switching properly between 0.1ish and 0.9ish and downstream are reading 0.1ish, then the cats are ok.

 

Plus they would be throwing specific codes for cat or o2.

Is p0171 the only code? That's more like vacuum leak or MAF issue. Possibly torn intake hose between MAF and throttle body

 

Only code is p0171. I went through a few cans of starting fluid and took everything apart looking for leaks. I don’t know, the 02 sensors were reading close to the same pre cat bank 1 and 2 so I think the cats are good

 

In your last 2 pics, you’re not up to operating temp @ 120 which needs to be approx 180, which means most readings of O2 sensors are going to be schewed until the cats/O2 sensors are warm enough. I do like your mew MAF reading of 4.1 which is close to normal. Many folks say the rule of thumb for MAF is approx eng size….4.7 +-.5. I also like the ambient temp of 77. PA is in the 80’s this morning. Your earlier IAT reading was 109. Makes me wonder if you cleaned MAF or checked connection. Something made MAF/IAT readings to become better/normal.

I do agree on buying Denso sensors but do not agree just yet from the readings shown that one would automatically buy high dollar cats.

 

I'd clean the MAF with MAF cleaner not anything else then reset codes and drive it

 

Wouldn’t maf or fuel issue read on both sides, 0171 is bank 1 so drivers side only?

 

I did unplug the maf for a minute

 

Not necessarily, as mentioned earlier, ECM was seeing lean condition and dumped more fuel to compensate….hince, high long term fuel trim.
This is just one of many links explaining P0171 and different things to check and/or replace.

https://parts.olathetoyota.com/p0171-code-toyota

As mentioned a few times, clean MAF, sensor preferably with CRC MAF cleaner and while you’re at it, clean throttle body with CRC throttle body cleaner. Also consider getting good Denso sensors front and rear.