2004 Tacoma 3.4L stuttering when accellerating

Light misfiring (?) when accelerating, most frequently 45 mph or higher when in overdrive (taking out of overdrive to downshift/increase rpm's prevents misfiring), sometimes when idling at low rpm's, and occasionally other times when accelerating.

Maintenance done either recently or after started stuttering: replaced fuel filter, air filter, master airflow sensor (after trying to just clean first), spark plugs and plug wires. The oxygen sensor leading into the engine has been replaced but not the one on the exhaust (wrong part was sent).

There are no longer any codes being thrown (oxygen sensor initially, then misfire at cylinder 1 but the new spark plug was bad). I am looking for any suggestions and thoughts. Thanks!

 

1. Brand of new mass air flow sensor?

2.
last time timing belt & related components was replaced?

3. total mileage?

 

Vacuum leak or injectors.

 

Your conditions are max load for the engine. Spark plugs gapped properly? Ignition coils ever replaced?

The 04 also has issues with its drive-by-wire system

 

227000 miles and it’s about due for the timing belt replacement. The MAF was just a NAPA part…

coils are original

 

The wires are stamped with a date if oem, if they are original I would start with the wire set and spark plugs before replacing coils.

 

So I cleaned the throttle body this weekend, good to do but not a fix. I could not find a vacuum leak, and using a timing light the coils all seem to be working just fine.

The new MAF was NAPA brand.

So... is the next step probably to look at the injectors (I do need to replace the timing belts as the current is at 102 K, but I don't know that this is causing the stuttering)?

 

Same symptoms I had when my injectors were bad, and about the same miles on the odometer. Only difference is I was getting a misfire code almost every time it stuttered. I rearranged the injectors and the misfire code followed to the new cylinder. New injectors fixed it.

 

Misfire diagnosis should always start with an inspection of the secondary ignition.