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Toyota Service
Toyota Service, Toyota Expert
Category: Toyota
Satisfied Customers: 4840
Experience:  30+ Yrs of auto experience, Award Winning Svc. Manager; Just Answer Customer's Choice Award Winner
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03 Toyota Camry 2.4L cold start stumble on acceleration once

Customer Question

03 Toyota Camry 2.4L cold start stumble on acceleration once vehicle arms up still stumbles a little but when you shut vehicle off long crank time to start and intermittent no start. new parts include fuel pump, injectors, maf, air/fuel sensor, o2 sensor, plugs. cleaned the throttle body. Also code P0171 stumped here please help
Submitted: 1 year ago.
Category: Toyota
Expert:  Toyota Service replied 1 year ago.

Hello. Welcome to Just Answer. Please allow me to assist you. The P0171 code is most likely the cause of all of your issues. You would want to make sure that you have no vacuum leaks at any of the rubber hoses in the engine area, and take special care to look at the main air tube between the air filter and the engine. Any cracks or leaks will result in this air leak not being measures by the MAF. Make sure the clamp is tight at the throttle body...Any air leak will set a P0171 code. The P0171 indicates a problem with the mass air flow )or "MAF"). If you have no leaks anywhere, the next thing you need to do is get another MAF. A faulty (or dirty) MAF will set a P0171 code. When this code is set, the MAF is not sending the proper information to the ECM. A good MAF, with no aire leaks will not set a P0171 code.

Customer: replied 1 year ago.
Replaced the MAF and smoke tested the intake on both side of the throttle body. This car is very clean old person driven with 83000 miles
Expert:  Toyota Service replied 1 year ago.

What is the fuel pressure reading after the vehicle has sat for 8 hours?

Customer: replied 1 year ago.
Never measured that it starts perfect when cold at 50 psi but will stumble till it dies if you dont baby the throttle. Fuel pressure never drops below 50 psi when you shut vehicle off and it sits for an hour pressure doesnt drop below 45 now in 8 hours not sure. But when engine hot 50 psi it has a long crank time. I also pinched off purge valve supply vaccum to be sure purge valve is out of question
Expert:  Toyota Service replied 1 year ago.

No history or pending codes? Just the P0171?

Customer: replied 1 year ago.
No history or pending just p0171 after about 4 key cycles and driving 10 miles it resets every time. I just cleaned throttle body again and cleaned MAF. Smoke tested engine itself through valve cover port. Smoke tested both sides of throttle body again as well. We put a new fuel filter,fuel pump,injectors,plugs,valve cover gasket,pcv valve, air filter is clean the rubber intake book is perfect not even age cracks. Im totally stumped
Expert:  Toyota Service replied 1 year ago.

Attach your scan tool to the engine when it is cold. Set it to monitor the loop status. See if the problem occurs right between the change from open to closed loop.

Customer: replied 1 year ago.
Open loop vehicle starts great but stutters very bad at partial throttle. Closed loop still stutters slightly but definatly not as bad. When vehicle is hot if you shut car off and crank it right back up is has a long cranking aprox 5 seconds. The longer it sits the worst it gets till it cools down. starts within 1 second when cold but stutters till it dies if you hold throttle open. St fuel trim hot is -13.3 and Lt fuel trim is 14.8 Maf gr/se 3.78 coolant temp 183
Expert:  Toyota Service replied 1 year ago.

Please clear the code and retest with the PCV hose pinched shut

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