My car surges while driving down the road. There is no check engine light. Have replaced plugs, wires, all coils, fuel filter and had smoke test for vacuum leaks done. Nothing helped. Please help. it is a 2001 Monte Carlo 3.4.
Car surges while driving down the road
Could be a failing ignition control module as this is one of the most common failure components. But may also be something else. A failing sensor. A clogged EGR or catalytic converter. Loose or damaged wiring harness. May also be a transmission issue occurring. Hard to tell without experiencing it for myself if it is engine or transmission related. Makes it even more difficult without any stored codes. Even though there is no check engine light on, there may be codes stored. So make sure you at least have them checked. Take note to see if this only occurs after the engine has warmed up or happens even when cold.
Check your wiring harness
Look at the wiring harness for damaged or brittle wires. Pay close attention tot he wiring and connections at both crankshaft position sensors, camshaft position sensor and Interrupter ring mounted on the back of the balancer.
Ignition System Modes of Operation
Anytime the PCM does not apply 5 volts to the Ignition Control timing signal circuit, the Ignition Control Module controls ignition by triggering each coil in the proper sequence at a pre-determined dwell. This is called Bypass Mode ignition used during cranking and running below a certain rpm, or during a default mode due to a system failure.
When the PCM begins receiving 24x reference and 3X reference pulses, the PCM applies 5 volts to the IC timing signal circuit. This signals the IC module to allow the PCM to control the dwell and spark timing. This is IC Mode ignition. During IC Mode, the PCM compensates for all driving conditions. If the IC mode changes due to a system fault, the IC mode will stay in default until the ignition is cycled OFF to ON, or the fault is no longer present.
Powertrain Control Module – PCM
The PCM is responsible for maintaining proper spark and fuel injection timing for all driving conditions. Ignition control (IC) spark timing is the method the PCM uses to control spark advance and ignition dwell. To provide optimum driveability and emissions, the PCM monitors input signals from the following components in calculating ignition control (IC) spark timing:
- Ignition control (IC) module
- Engine coolant temperature (ECT) sensor
- Intake air temperature (IAT) sensor
- Mass air flow (MAF) sensor
- Internal Mode or PNP inputs from Internal Mode switch or Park/Neutral position switch
- Throttle position (TP) sensor
- Vehicle speed (VSS), or transmission output speed (TOSS) sensor