*Acknowledges the forbidden nature of New Account/Troubleshoot Help request thread. * With that out of the way, let me preface by saying: Yes, I have gone through the forums, checking for issues similar to mine. I already have a list of likely issues, and I am mostly wanting a “sanity check” so-to-speak to see if others point out obvious things I am missing. Vehicle Info: 2011 Prius II, Approx 260K Miles, Southern California, Frequent hard up-hill freeway driving. Average Maintenance Routine: Oil 5K miles, Air Filter 20K miles. Traction Battery replacement 100K miles ago. Acc Battery replacement 20K miles ago. Major engine rebuild 30K miles ago (Coolant change, spark plug change, Head Gasket chant, injector cleaning/change, EGR valve/cooler cleaning, PCV change). ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Beginning at the start of summer, the average MPG loss thanks to AC running look my average 48 mpg down to 45-46, with steady decrease over course of 2 months, and an overall feeling of sluggishness. No improvement with oil change, use of high mileage Techron, air filter change, acc battery exchange. No CEL, no misfires. Confirmed sensors were active using OBD tool and old fashion pulling (undoing each injector and MAF, confirming the ECU immediately shut down engine and generated trouble codes) Began using Hybrid Assist and Dr. Prius, confirmed battery health at higher than average for milage. Began recording STFT and LTFT data: STFT peak and dip before leveling to 0% as expected but appear to lag compared to recording others have made (taking on average 5-7 seconds to level out once engine RPM has stabilized). LTFT initially reported consistent lean of 4%-12% when idling, spiking nearly to 20% under acceleration at +85% load. LTFT have continued to steadily rise over the course of summer and fall, now sitting at 23% idle, with STFTs “bouncing” more often like ECU is trying to adjust. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Finally generated first CEL with code p0171 while driving uphill on freeway. All freezeframe data appears “normal” or as expected for a lean condition, save for EGR% at 65% (will include photos of freeze frame data below). Did a “cheap vacuum leak check” (can of spray carb cleaner), found no notable change in RPM despite near saturating of all connections between MAF and throttle body, around intake manifold, spark plugs, EGR valve/cooler/pipe, PCV valve. Confirmed RPM would surge when cleaner was directly sprayed into air intake. Disassembled ERG valve and performed cleaning in case plunger rod/spring was sticking, found expected carbon build up but no where near complete blockage (approx. less than 1mm around walls of EGR connection pipe). No improvement after cleaning, reassembly, and second vacuum leak check. Current LTFT 23%, STFT still “jumpy.” I suspect a failing fuel pump/clogged fuel filter/clogged regulator, as all parts are original and the tar glue around the pump cover appears intact with no evidence of scrapping. However, before doing a fuel pressure test, and replacing the entire assembly unit, I want to make sure I am not overlooking anything besides the usual suspects: O2 Sensors, MAF sensor, EGR, Injectors, Vacuum leaks, etc. Essentially “check my homework” please. *CEL freezeframes:
Unrelated/"Horse Sense": Significant difference between MPG estimate from ECU and IRL estimates. Before the summer, the ECU estimated was on average 48-49mpg, with IRL values (literally divide trip miles by at pump amount) usually being 1-1.5 lower (as to be expected). As of the last refill, the ECU estimate is 42mpg, with IRL 49mpg. The prius ECU is well known for not having accurate estimates, so it's likely a coincidence, but it is interesting that [42\49]=approx 86%, while the LTFT shifts between 15% and 22% when cruising at around . Almost as if the ECU believes it's adding more (thus recording) more fuel, while it's IRL fuel consumption implies it's simply adding "enough."
I don't know buddy but fuel pumps are cheap Toyota has been using the same fuel pump since 85 practically they're in my Italian scooters too . The Toyoda femurl pump that is . If it's encased in a plastic housing all that unsnaps and you can replace the fuel pump in this Gen . At 260,000 mi you would think it's time although Ihav a Corolla w 500 plus K w original ego pump still Intact . The car has been with us since the day it was rolled off the showroom floor I know it's never been changed anditd past time car runs fabulous
The freeze frame data for the long-term fuel trim is showing 37.5%. I am guessing that you have a vacuum leak in a hose. The most probable place is the hose that runs from the intake manifold near the throttle body over to the purge valve. The hose on the other side of the purge valve probably also has cracks in it where it attaches to the purge valve. Take the air box off and take a look at those two hoses. I replaced those two hoses on my niece's 2010 Prius early this year. Her car also had the P0171 code. I also checked my 2011 Prius and the same two hoses.had just started to develop cracks, but it was not bad enough to trigger the code yet. I believe this is a common problem for a 15 year old Prius. Here are pictures of both ends of one of the hoses that I replaced on the 2010 car.
*Update Shortly after the initial post, my prius began throwing the code p0171 every time it was driven hard enough uphill or on the freeway that the engine RPM rose into the high 3k’s and 4’s. It also developed a pronounced “whirr” from under the driver’s side rear seat, confirming the fuel pump as the primary culprit. I initially tried to buy the entire pump, filter, regulator, fuel level gauge, assembly out the door from the dealership, however the sales clerk cancelled my original order, then insisted that in order to maintain the warranty the ENTIRE TANK needed to be replaced, instead of simply drained, and cleaned out. Against my better judgement, I just bought the replacement from AutoZone, though they only had a Delphi available, not the Denso that the dealership would provide. Replacing the fuel pump saw the immediate disappearance of CEL and fuel trims fall back down towards more reasonable levels (LTFT +3 to +5). However, the replacement immediately had issues with the fuel gauge reporting incorrect levels, frequently reporting fuel levels nearly half a gallon less than what was actually in the tank. From full, the gauge would drop to approx. 9 gallons at only 25-30 miles at an estimated 47 mpg, with similar patterns of reporting 8 gallons at 75 miles, 7 gallons at 120, all the way to reporting only 1 gallon remaining after only 380 miles. In each instance, refilling would have the gas pump indicate that it put in less than what the gauge was reporting missing (in the case of only 1 gallon remaining at 380 miles, the gas pump filled the tank only 7.9 gallons. All possible inconsistencies of gas station pumps aside, it’s clear the new fuel pump at least has issues with it’s fuel gauge sensor as not only is the level considerably incorrect, but it’s frequently “flickers,” sometimes immediately displaying loss of 1 gallon after filling up, just to flicker on and off until remaining steady at the aforementioned 25ish miles, and this behavior repeating at other points as the fuel level drops. More concerning, the new pump appears to already be suffering from dropping pressure, as its LTFTs have consistently risen, now sitting at about +7 to +10% when idling, and raising at much at 14% when under high load. STFTs are more consistent with the new pump, only raising about +3 to +5% when the accelerator is suddenly floored, before quickly returning to 0%. This varies depending on weather and humidity, with dry days causes higher fuel trims, and colder, extremely humid days like those around coastal parts of orange county and Los Angeles, resulting in much lower fuel trims. This could likely indicate issues with the MAF sensor under-reporting air flow, causing it to request higher fuel trims to correct for a perceived lean condition; However I suspect it is primarily an issue with the fuel supply as the ECU is still considerably underestimating it’s fuel economy compared to actual fuel consumption based on distance traveled and fuel being added. The most recent fill up had the fuel consumption estimate at 46.2, where else real world fuel consumption was approximately 48.9 mpg. I’m curious if there is a relation between the faulty fuel gauge level and the Prius’ ECU consistently under estimating it’s own fuel economy; or if it simply is the new fuel pump running weak, resulting in the +7 to 10% LTFT and the ECU believing it’s using more fuel than it actually is. Regardless, I’m debating calling various dealerships around SoCal and seeing which will sell me the OEM Denso pump assembly WITH warranty, without requiring they do the work and requiring an entirely new fuel tank be put in. I really don’t want to have to buy another Delphi from AutoZone given this was the only a name brand pump available and its having potential gauge and pressure issues after less than 2 months. I’m curious if I’m still overlooking obvious things or potential causes for the LTFTs and seemingly difference between estimated and real-world fuel consumption. I’m getting tired of the sudden behavior of me driving hard up one hill, and it’ll drop from 47mpg to 43mpg over the course of 3 miles, then I can coast down it the very next morning, and it’ll only return to back to 44.5, when it never had that behavior before the previous fuel pump started dying. *I will also underline. I have already tested for vacuum leaks. Fuel injectors and rail have been cleaned/replaced during the previous engine rebuild. All other routine maintenance is still being completed, including the EGR cleaning after the rebuild.
