Symptom
Hesitation or stumble under acceleration
A momentary flat spot or stutter when the throttle is opened, often at a particular pedal position or engine speed. Where it happens consistently at one point in the range, that repeatability is itself diagnostic.
Also described as: hesitation, stumble, flat spot, bogging down, stutter, surge, jerking, kangarooing, misfires under load, coughing, هنگام گاز دادن مکث میکند, موقع شتاب گیری لگد میزند, گاز نمیخورد, tirones al acelerar, duda al acelerar, se ahoga al acelerar, jalonea al acelerar, السيارة تقطع عند الدعس, تقطع لما أدعس, تقطيع عند التسارع, ترددات عند الدعس, تختنق عند التسارع, نقزات عند البنزين
Some causes mean you should stop driving
59 of the 256 codes that produce this symptom indicate a fault where continuing to drive risks damage or is unsafe. If the symptom is sudden or severe, treat it as one of those until a scan says otherwise.
What this usually means
Repeatability is the diagnosis here, and the driver usually has it before anyone measures anything. A stumble that happens at the same pedal position or the same engine speed every time is a different fault from one that appears at random, and the distinction is worth extracting carefully because it halves the work.
A stumble at one repeatable point is a transition being handled badly. Engines change behaviour at defined thresholds — a variable valve timing phase, a variable intake runner flap, a boost threshold, closed to open loop, the point where extra enrichment is added for acceleration. A component that is slow or sticky at one of those transitions produces a flat spot in exactly the same place every time and nowhere else.
A stumble that appears under sustained demand is a supply ceiling. Japanese references put it plainly: when the injection quantity is increased for acceleration and the supply cannot keep up, the mixture goes momentarily lean and the engine catches its breath. That is a fuel filter, a tiring pump or a partly blocked injector, and it shows on a pressure gauge under load while looking perfect at idle.
And a stumble that comes with a misfire count is combustion rather than delivery. Ignition breaks down under load long before it fails at idle, because cylinder pressure demands more voltage exactly when the coil has least to give — so a worn plug gap produces a stumble under acceleration and a perfectly smooth idle.
Injector fouling deserves a specific mention because of who gets it. Japanese sources note that cars doing repeated short journeys, or standing for long periods, accumulate deposits as fuel degrades — so the complaint tracks the use pattern rather than the mileage, and a low-mileage car that mostly sits is a candidate where a high-mileage motorway car is not.
Working through it
| What you find | Likely cause | How to confirm it | What fixes it |
|---|---|---|---|
| Flat spot at the same engine speed or pedal position every time | A transition handled badly — variable valve timing, an intake runner flap, or the boost threshold | Log live cam position, flap position and boost across the exact point it happens. The repeatability is what makes this loggable at all. | Free or renew the actuator the log names. Check oil level and grade first where variable valve timing is involved. |
| Stumbles under sustained hard acceleration, fine on light throttle | A fuel supply ceiling — filter, pump or a restricted line, adequate at low demand | Gauge fuel pressure under load rather than at idle. On a diesel, watch live rail pressure against the commanded value during the stumble. | Renew the filter first where due, then the pump on the loaded measurement rather than on age. |
| Misfire counts rise during the stumble | Ignition breaking down under load — worn plug gaps or a failing coil | Read counters per cylinder during a loaded road test. Check plug gaps against specification; wear increases the voltage demand exactly when least is available. | Renew plugs as a set to specification, and the coil the counts name. |
| Low mileage, mostly short journeys or long periods standing | Injector deposits — degraded fuel leaves residues that spoil the spray pattern | The use pattern is the evidence. Corroborate with fuel trims and, where available, injector correction values. | A proper injector clean, or renewal where the spray pattern has gone. This tracks use rather than mileage. |
| Hesitation with lean trims and a hiss under the bonnet | Unmetered air entering downstream of the meter, worst where airflow is lowest | Smoke-test the induction including the servo hose and crankcase ventilation path. | Renew the leaking hose or gasket, then re-check trims. |
| Hesitation only when cold, gone once warm | Warm-up enrichment wrong for the actual engine temperature — usually the coolant temperature signal | Compare live coolant temperature against ambient on a genuinely cold engine; they should agree after a night's stand. | Renew the temperature sensor and inspect its connector for corrosion. |
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Flat spot at the same engine speed or pedal position every time
- Likely cause
- A transition handled badly — variable valve timing, an intake runner flap, or the boost threshold
- How to confirm it
- Log live cam position, flap position and boost across the exact point it happens. The repeatability is what makes this loggable at all.
- What fixes it
- Free or renew the actuator the log names. Check oil level and grade first where variable valve timing is involved.
-
Stumbles under sustained hard acceleration, fine on light throttle
- Likely cause
- A fuel supply ceiling — filter, pump or a restricted line, adequate at low demand
- How to confirm it
- Gauge fuel pressure under load rather than at idle. On a diesel, watch live rail pressure against the commanded value during the stumble.
- What fixes it
- Renew the filter first where due, then the pump on the loaded measurement rather than on age.
-
Misfire counts rise during the stumble
- Likely cause
- Ignition breaking down under load — worn plug gaps or a failing coil
- How to confirm it
- Read counters per cylinder during a loaded road test. Check plug gaps against specification; wear increases the voltage demand exactly when least is available.
- What fixes it
- Renew plugs as a set to specification, and the coil the counts name.
-
Low mileage, mostly short journeys or long periods standing
- Likely cause
- Injector deposits — degraded fuel leaves residues that spoil the spray pattern
- How to confirm it
- The use pattern is the evidence. Corroborate with fuel trims and, where available, injector correction values.
- What fixes it
- A proper injector clean, or renewal where the spray pattern has gone. This tracks use rather than mileage.
-
Hesitation with lean trims and a hiss under the bonnet
- Likely cause
- Unmetered air entering downstream of the meter, worst where airflow is lowest
- How to confirm it
- Smoke-test the induction including the servo hose and crankcase ventilation path.
- What fixes it
- Renew the leaking hose or gasket, then re-check trims.
-
Hesitation only when cold, gone once warm
- Likely cause
- Warm-up enrichment wrong for the actual engine temperature — usually the coolant temperature signal
- How to confirm it
- Compare live coolant temperature against ambient on a genuinely cold engine; they should agree after a night's stand.
- What fixes it
- Renew the temperature sensor and inspect its connector for corrosion.
Codes that produce this symptom (256)
Listed with the codes that most typically present this way first — the likeliest place to start.
- P0002 Fuel Volume Regulator A Control Circuit Range/Performance Typical of this code Stop driving High
- P0046 Turbocharger/Supercharger Boost Control A Circuit Range/Performance Typical of this code High
- P0068 Manifold Absolute Pressure/Mass Air Flow — Throttle Position Correlation Typical of this code Stop driving High
- P0087 Fuel Rail/System Pressure — Too Low Bank 1 Typical of this code Stop driving High
- P0089 Fuel Pressure Regulator A Performance Typical of this code High
- P008A Low Pressure Fuel System Pressure - Too Low Typical of this code High
- P0100 Mass or Volume Air Flow Sensor A Circuit Typical of this code High
- P0101 Mass or Volume Air Flow Sensor A Circuit Range/Performance Typical of this code High
- P0102 Mass or Volume Air Flow Sensor A Circuit Low Typical of this code High
- P0104 Mass or Volume Air Flow Sensor A Circuit Intermittent Typical of this code Moderate
- P0106 Manifold Absolute Pressure/Barometric Pressure Sensor Circuit Range/Performance Typical of this code High
- P0120 Throttle/Pedal Position Sensor/Switch A Circuit Typical of this code Stop driving High
- P0121 Throttle/Pedal Position Sensor/Switch A Circuit Range/Performance Typical of this code Stop driving High
- P0124 Throttle/Pedal Position Sensor/Switch A Circuit Intermittent Typical of this code Stop driving High
- P0131 O2 Sensor Circuit Low Voltage — Bank 1 Sensor 1 Typical of this code Moderate
- P0148 Fuel Delivery Error Typical of this code Stop driving High
- P0151 O2 Sensor Circuit Low Voltage — Bank 2 Sensor 1 Typical of this code Moderate
- P016C Closed Loop Air/Fuel Ratio Control At Limit - System Too Lean Typical of this code Moderate
- P0170 Fuel Trim Malfunction — Bank 1 Typical of this code High
- P0171 System Too Lean — Bank 1 Typical of this code High
- P0173 Fuel Trim Malfunction — Bank 2 Typical of this code High
- P0174 System Too Lean — Bank 2 Typical of this code High
- P0191 Fuel Rail Pressure Sensor Circuit Range/Performance Bank 1 Typical of this code Stop driving High
- P0194 Fuel Rail Pressure Sensor Circuit Intermittent/Erratic Bank 1 Typical of this code Stop driving High
- P0220 Throttle/Pedal Position Sensor/Switch B Circuit Typical of this code Stop driving High
Information, not instruction
CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.
Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
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