My 2011 Honda Accord will not go over 20 mph, RPM rises. Reads diagnostic codes P0171, P0420 and P0303. What could the problem be?

Since a P0171 can cause a P0420, you'd want to diagnose and fix the cause of the P0171 first. Here's an article on what to check when you have a P0171 https://ricksfreeautorepairadvice.com/fix-p0171-system-too-lean-trouble-code/

My sputtering & stalling 1993 Honda Accord - YouTube

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https://www.youtube.com/watch?v=Ki2H9aq8Xis
Jun 23, 2011 - Uploaded by mdpbfly
My sputtering & stalling 1993 Honda Accord ... 1996 Acura Integra, hesitation accelerating & misfire. ... 1993 Honda Accord Start Up and Review 2.2 L 4-Cylinder ... SIR B16A Engine sputter/ power loss at higher RPM - Duration: 1:14. by ... 1994 Honda Civic Check Engine Light Code Retrieval Tutorial ...

All comments on How To Solve Honda Idle Problems ...

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Acceleration Bog/Sputter/Hesitation - Honda-Tech

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Jun 11, 2010 - 1990 Honda Accord Ex F22 209000 miles, recent alternator change When I ... When I take off from a stoplight I get a little hesitation/bogging/sputteringfeeling until about 2,000 RPM then ... My 1999 Accord had a similar problem (F18B2engine). ... It only lasted a second or so before it would actually rev up.

2000 Toyota Corolla, P0171 & P0420 codes - YouTube

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https://www.youtube.com/watch?v=ahJnJ19-vwY
Jun 13, 2011 - Uploaded by StandardBrandParts
Standard Motor Products presents: Technician's Toolbox "2000Toyota Corolla, P0171 & P0420 codes"

Smoke testing for codes P0171 P0174 - YouTube

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https://www.youtube.com/watch?v=kZsqEfP-5zM
Jan 18, 2011 - Uploaded by realfixesrealfast
These two codes mean a V style engine is running lean on both banks. So you have to be thinking - what can ...

How to repair fault code P0171 and reset warning light ...

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Nov 27, 2014 - Uploaded by Peter Finn
How to repair and fix fault or error code P0171 and reset warning light Toyota Corolla VVT-i engine. ... Also how to find fault codeusing OBD scanner. ... Trouble shooting a misfire, Code P0300, P0301, P0302, P0303, P0304, P0305, P0306, ... 2000 Toyota Corolla, P0171 & P0420 codes - Duration: 5:43. by ...

run fault codes and check for TCM failure as it appears that the OD section is not working Although the compression appears low a constant 125 psi is an indication of a good motor and remember that the amount of oil used will increase the compression pressures if the rings are good . It would be of concern if a cylinder with oil did not respond with a rise in compression indicating weak rings are scored bore. Have an oil pressure test done on the gear box to ensure that every thing inside is as it should be and check the band/clutch adjustment as the rpm at 60 mph should be around 3200rpm

Standard Shift? Clutch is Slipping

Automatic? It is coming out of gear or slipping

If it is an automatic-- you most likely will end
up having to rebuild it,if it is original since built for yr 2000

More than likely the catalytic converter has failed. the computer looks at the downstream O2 sensor to determine if the cat is working. If it sees the downstream O2 starting to switch back and forth like the upstream O2 or read consistently higher than it should than it will flag the P0420 code.

I’m happy to assist further over the phone at https://www.6ya.com/expert/jeremy_d728a59f986299fa

I never say a code call "end of net" before, are you sure? Code are usully PXXXX(example:P0420,P0300, etc...). You might want to have it double check.
good luck

could be a couple of things try checking your codes for proper diagnostics it can be done at home usung a paper clip look on youtube for video directions

P0171 code is described as: lean condition bank 1, oxy sensor 1. If your vehicle is a 4 cylinder, which I believe it is.. you have got a lean air/fuel mixture being found by the ecm(computer).This can be caused by several things. The first of which is a possible vacuum leak at or near the intake manifold. This can also be caused by a MAF(Mass Air Flow) sensor problem or even by something as simple as a clogged fuel filter. This lean condition could also be the cause of the P0420 :described as a catalyst efficiency problem. It would be best to have the vehicle taken to a reputable repair facility that is capable of engine performance diagnostics and have them run tests for these codes. The gasket you mention is most likely a valve cover gasket not the head gasket and would not cause these codes. Although you should have this leak fixed before it becomes a problem.

Hope this helps..

You Definatelly got some Bad Fuel. Get a can of B-12 Chemtool from any Auto Parts Store or Wal-Mart and Pour it in the Gas Tank then Let it Run for a While. Should help Dramatically! Let me know!