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Nancy 7/15/2019

1997 Toyota 4Runner Base 4 Cyl 2.70L


Stalling / shuddering

I bought this car new and have kept up with all regular maintenance recommendations. It has approx 200k miles. Last week on the freeway, while pressing the gas, the car shuddered and acted like it wanted to stall, but did not stall. The check engine light came on immediately. It was riding very rough and continued to shudder. I took the car straight to Toyota, but they found nothing after running diagnostics.
Leaving Toyota, the car shuddered again on the freeway, I think I was accelerating past 50 mph, and again the check engine light came on. It now shudders and feels like it will stall when accelerating from a stop or at high speeds. It does not stall, but the car is shaking. I have heard no noise when this occurs. I have another app with Toyota, and they are scheduled to drive it with me in order to experience the problem. They are also giving the car to a diff 'team' for fresh eyes, etc.
Does anyone have any ideas about what this might be?

1 Answer


Jimm 7/16/2019

First step - have the stored fault codes or check engine light scanned - for free - at any local auto parts store; Advance Auto, Auto Zone, NAPA.

Avoid the dealerships with a 20 year old vehicle!

Then, post a reply as 'add answer' with the specific code for more assistance.

This aspect is important; there may be a fault code stored in the OBD memory which may not be displayed as a check engine light.

Do not skip this important first step - there are literally hundreds of possible fault codes. Avoid wasting/ throwing money at the problem.

Possible Causes of Engine Hesitation or Stumble:

Dirty fuel injectors (cleaning the injectors often fixes this)
Dirty air filter (change filter)
Dirty / clogged fuel filter (change filter)
Bad MAP (manifold absolute pressure) sensor
Bad TPS (throttle position) sensor
Bad or dirty MAF (mass airflow) sensor
Low fuel pressure (leaky fuel pressure regulator or weak fuel pump)
Vacuum leaks (intake manifold, vacuum hoses, throttle body, EGR valve)
Bad gasoline (fuel contaminated with water or too much alcohol)

Sometimes, what feels like a hesitation is actually ignition misfire rather than lean misfire. The causes of ignition misfire may include:

Dirty or worn spark plugs
Bad plug wires
Weak ignition coil
Wet plug wires


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