1999 Toyota 4Runner Miss fire

DUDE1888

MEMBER
1999 TOYOTA 4RUNNER
6 CYL
2WD
AUTOMATIC
139,000 MILES

When I start my 4runner in the morning or when the engine is cold, it runs perfectly and will continue to do so for as long as it is running. But if I stop and turn it off, it missfires in the #1 cyclinder. This is ony afetr it is warm. After about 5-10 mins of driving it will eventualy smooth out until I stop again. The check engine is on and the code is P0171.

Just a recap:
Runs fine when cold and will continue for as long as I drive it

Misses when turned turned off and sit for about 15mins and turn back on, and it really runs kike crap.

Will smooth out after about 5-10 mins of dirving until I turn it off again.

Does this sound like an MAS?

3 Replies

RASMATAZ

MECHANIC
75,992 POSTS

P0171/P0301

A lean fuel condition can be caused by:

* Low fuel pressure due to a weak pump or leaky fuel pressure regulator. (Use a fuel pressure gauge to check fuel pressure at idle)

* Dirty fuel injectors. (Try cleaning the injectors)

* Vacuum leaks at the intake manifold, vacuum hose connections or throttle body. (Use a vacuum gauge to check for low intake vacuum)

* Leaky EGR valve. (Check operation of EGR valve)

* Leaky PCV Valve or hose. (Check valve and hose connections)

* Dirty or defective Mass Airflow Sensor (MAF). (Try cleaning the MAF sensor wires or filament with aerosol electronics cleaner. Do NOT use anything else to clean the sensor, and do not touch the sensor wires)

P0301 check the sparkplug/injector/compression on that cylinder