* Transmission Problems: This is the most probable cause. Issues like:
* Torque Converter Clutch Problems: A slipping or malfunctioning torque converter clutch can cause jerking, especially during acceleration or shifting.
* Transmission Linkage/Cables: Worn or adjusted improperly, these could cause erratic shifting.
* Shift Solenoids: These electronically control shifting; a faulty one leads to inconsistent shifts and jerking.
* Low Transmission Fluid: Low fluid level or contaminated fluid can cause slippage and jerky behavior. Check the fluid level and condition (look for burnt smell or discoloration).
* Worn Transmission Components: Internal transmission wear (bands, clutches, etc.) is more likely in a car of this age and will cause various shifting problems, including jerking.
* Engine Problems: While less likely to cause a *forward* jerk specifically (more likely to be a general hesitation or stumble), engine issues can indirectly contribute:
* Spark Plugs/Wires: Misfires can cause inconsistent power delivery, possibly leading to a jerky feel.
* Ignition System Problems: A weak coil, distributor cap, or rotor could result in misfires.
* Fuel Delivery Issues: A clogged fuel filter, faulty fuel pump, or injector problems can cause a lean condition and inconsistent power, potentially manifesting as jerking.
* Vacuum Leaks: Leaks in the vacuum system can disrupt engine timing and fuel delivery.
* Computer/Sensor Issues: The 1988 Bonneville likely has a computer-controlled system. Issues with sensors feeding information to the computer can lead to erratic behavior:
* Throttle Position Sensor (TPS): A faulty TPS can cause incorrect fuel/air mixture calculations leading to jerky acceleration.
* Mass Air Flow Sensor (MAF): Similar to the TPS, a faulty MAF sensor provides incorrect information about the air intake.
Troubleshooting Steps:
1. Check Transmission Fluid: This is the easiest and first thing to check. Low or dirty fluid is a major culprit.
2. Listen for Unusual Noises: Pay attention to any unusual noises coming from the transmission while driving. Grinding, whining, or banging could indicate internal problems.
3. Check Engine Light: If the check engine light is on, have the codes read using an OBD I scanner (this is important as OBD II wasn't standard until 1996).
4. Professional Inspection: Given the age of the car and the complexity of potential issues, a professional mechanic familiar with older vehicles is recommended for proper diagnosis and repair. They have the tools and experience to properly diagnose the problem.
It's crucial to have a mechanic diagnose the problem before attempting any repairs yourself, as improperly diagnosing and fixing transmission or engine issues can lead to more extensive and costly damage.
