Does your Jeep feel sluggish under acceleration? Does it misfire when you depress the gas pedal? Have you been to a car wash lately or used a high-pressure hose while cleaning? If you answer yes to any of these questions, then the following article will have the possible cause and solutions for you.
A Jeep Wrangler needs the correct ratio of 14.7–to–1 air/fuel necessary for proper engine operation. An incorrect ratio of fuel and air will cause the Jeep to Jerk under acceleration. Other common causes for Jeeps to jerk while accelerating are:
- Bad alternator
- Bad Upstream O2 sensors
- Bad Spark Plugs
- Bad Battery
- Clogged Fuel Filter
- Faulty Crank Position Sensor
Most conventional gas-powered vehicles, including the Jeep Wranglers, require three elements to run properly. Those 3 elements are a very specific mixture of air, fuel, and electrical spark. If any of those 3 elements are missing or out of spec, it will cause the vehicle to run poorly, jerk, and even stall.
This article will discuss those elements in more detail, explaining the common causes for your Jeep Wrangler to jerk when accelerating, so stick around.
Why Is My Jeep Wrangler Jerking –CAUSES
The Jeep Wrangler has a few key electrical components that can cause it to jerk, so you will need to systematically inspect all of them as best you can to locate your culprit.
Electrical
Once an electrical component comes into contact with water or any fluid, it drastically reduces the functionality of that part. Something as innocent as using a high-pressure hose when cleaning your engine bay or driving through a car wash can cause electrical components to pick up moisture.
Let’s look at each component in more detail.
Alternator
A bad alternator is not something we can physically look at and detect that it is bad. Unless, of course, it’s completely burnt out, then you might notice some black traces around the outer casing, but generally, the only signs we have are those emitted by the behavior of your Jeep and the information being displayed on the instrument panel.
If you have a bad alternator, your instrument panel should display a battery symbol which indicates a fault and you have a “Battery Charging Condition” A bad battery that has a low charging voltage from the alternator will confuse my electrical sensors and can be the cause of jerking while under acceleration.
Upstream O2 sensors –
The basic structure of a modern exhaust system comprises a few components.
- exhaust manifold(s)
- exhaust pipe
- oxygen sensors
- catalytic converter(s)
- heat shield(s)
- muffler
- tailpipe
The Oxygen Sensors (O2S) are connected directly to the Jeeps exhaust system. Depending on the engine or emission package, the vehicle may use a total of either 2 or 4 sensors.
An O2 sensor is a galvanic battery that provides the PCM with a voltage signal (0-1 volt) inversely proportional to the amount of oxygen in the exhaust. In other words, if the oxygen content is low, which can be caused by a blocked or clogged up air filter, the voltage output is high.
On the other hand, if the oxygen content is high the output voltage is low. The PCM uses this information to adjust injector pulse-width to achieve the 14.7–to–1 air/fuel ratio necessary for proper engine operation and to control emissions. Any Ratio below or above this mixture ratio will result in your vehicle underperforming and jerking under load.
In the event any of the O2 sensors get water-damaged, you are recommended to replace all 4 and use only high-quality NGK sensors.
Spark plugs
In order for your Jeep to run smoothly, you need to ensure your sparkplugs are of good quality and in good condition. A plug that has been deposited on it will underperform and result in your Jeep fuel consumption increase and cause jerking while accelerating. Identification signs of a bad spark plug include:
- Light tan/grey in color on the tips
- Black electrodes caused by electrode burning
- Large Gaps
Your spark plugs gap will expand every 1000 miles of driving. This is referred to as “Gap growth”. Gap growth should not exceed more than roughly 0.025 mm (.001 in) per 1600 km (1000 miles) of operation.
A spark plug can be restored by doing the following:
| Step 1 | Remove the plugs |
| Step 2 | Thoroughly clean the plug |
| Step 3 | File the electrodes |
| Step 4 | Set the gaps |
| Step 5 | re-install |
CPS
Like most modern engines, the Jeep Wrangler makes use of a CPS (Crank Position Sensor) to monitor the position or rotational speed of the crankshaft and ignition timing. This information is then relayed to the engine management systems to control the fuel injection or the ignition system timing and other engine parameters. A faulty CPS can easily cause a misfire, poor engine performance, and jerking.
Battery
A bad battery that has a low voltage will result in incorrect voltage signals to be transferred to electrical components. This can also confuse many electrical sensors which can be the cause of jerking while under acceleration since they won’t relay the correct information to allow the engine to function optimally.
The most obvious signs of a bad battery are:
- Dim headlights
- Clicking sound when you try and start the engine
- Slow cranking
- Longer than usual cranking times
- Backfiring and jerking
The average life expectancy of a car battery is three years so check your battery age stamp to determine if you are due for a replacement. There are external factors that can result in your battery wearing/breaking down sooner such as environmental conditions and chemical reactions.
Next, let’s look at a few fuel-related aspects that can cause problems with acceleration.
Fuel
This section covers your fuel supply, pressure, and filters.
Fuel Filter
If you often fill up at dodgy filling stations, your fuel tank eventually becomes filled with all sorts of sediment that gets sucked up from the filling station tanks. This accumulates over time and the waste in the fuel filter could also cause the car to jerk. A clogged-up fuel filter is one of the most common causes for a jerking vehicle. When your Jeep gets its scheduled services, ensure only quality fuel filters get used to blocking all rust and sediment from entering your engine and clogging injectors, causing even further more expensive damage.
Another sign of a bad fuel filter is when you are driving up an incline or when the vehicle is under more load, this will also cause the vehicle to jerk, cut out, or lose power.
Fuel Pump
A bad fuel pump can be caused by running your tank too low too often or simply old age. There are gears inside the fuel pump that eventually wears out, resulting in a loud buzzing sound being emitted from the rear close to the fuel tank.
A bad fuel pump will result in your vehicle jerking when accelerating or when driving up an incline since it won’t be able to produce enough fuel pressure to supply your injectors.
Air
Idle Air Control Motor
The AIC motor is located on the rear side of the throttle body and regulates the amount of air bypassing the control of the throttle plate. When the engine loads and ambient temperatures change, engine rpm changes The IAC is controlled by the Powertrain Control Module (PCM) to maintain the target engine idle speed. A faulty AIC will result in decreased performance, jerking, and stalling.
Resources
Purchase a Replacement 4.0L Wrangler Alternator here
Purchase a 3.8 Wrangler Alternator Here
New 160A jeep Wrangler 3.6 Alternator
New Jeep Wrangler Upstream and Downstream O2 sensors
Purchase Jeep Wrangler NGK Spark Plugs here
Purchase a Wrangler replacement Crank Position Sensor here
Replacement Wrangler Red Top Battery
Complete Bosch Fuel Pump Assembly
Conclusion
Whatever the cause of your Jeep Wrangler jerking while driving, if you follow the above-mentioned guidelines, you can successfully identify which component is responsible for your vehicle’s behavior. Start your troubleshooting with the most common causes first such as the spark plugs, battery, and sensors. It’s always valuable to know the inner workings of your Wrangler, and doing a bit of DIY diagnosis can save you lost of time and money at the dealerships.