Check the coil packs and EGR:
Exhaust Gas Recirculation System
Application of the Exhaust Gas Recirculation (EGR) gases is regulated by the Powertrain Control Module (PCM). It is based on engine coolant temperature, engine speed, vehicle speed, throttle angle and Manifold Absolute Pressure (MAP). The operation of the EGR system is monitored by the PCM, which allows gases to flow at a calculated rate and compares it against MAP sensor and oxygen sensor activity. The PCM anticipates an increase in MAP voltage and an increase in O2 sensor voltage.
Electrically operated vacuum control solenoids used to control the flow of vacuum to the EGR valve, rely on pulse-width duty cycle commands from the PCM to control its operation. Using input values and the operating conditions previously mentioned the PCM completes the electrical circuit for the solenoid to allow vacuum operation of the EGR.
In addition to solenoids controlling vacuum flow, the incorporation of a back pressure transducer regulates vacuum signals independently of electrical signals. When back pressure in the exhaust system is low, the transducer pintle is open and manifold vacuum is allowed to bleed off. As back pressure increases the amount of vacuum allowed to bleed off is reduced resulting in more vacuum being applied to the valve. This allows air pressure to open the valve.
The following symptoms can be caused by a faulty EGR valve due to loose connection, bad grounds, high resistance in the circuit, or opens in the circuit.
- Stalling on deceleration
- Stall at idle
- Surging off idle
- Unstable idle
- Running rough off idle
- Low idle
- Poor fuel economy
- Spark knock
- Stalling on acceleration
Diagnosis and Testing
Secondary Spark Test
These spark tester looks just like a spark plug, attach the clip to ground and crank the engine to check for spark
This spark tester has an adjustable air-gap for measuring spark strength and testing different voltage ignition systems
Attach the clip to ground and crank the engine to check for spark
This spark tester is the easiest to use just place it on a plug wire and the spark voltage is detected and the bulb on the top will flash with each pulse
The best way to perform this procedure is to use a spark tester (available at most automotive parts stores). Three types of spark testers are commonly available. The Neon Bulb type is connected to the spark plug wire and flashes with each ignition pulse. The Air Gap type must be adjusted to the individual spark plug gap specified for the engine. The last type of spark plug tester looks like a spark plug with a grounding clip on the side, but there is no side electrode for the spark to jump to. The last two types of testers allows the user to not only detect the presence of spark, but also the intensity (orange/yellow is weak, blue is strong).
- Disconnect a spark plug wire at the spark plug end.
- Connect the plug wire to the spark tester and ground the tester to an appropriate location on the engine.
- Crank the engine and check for spark at the tester.
- If spark exists at the tester, the ignition system is functioning properly.
- If spark does not exist at the spark plug wire, perform diagnosis of the ignition system using individual component diagnosis procedures.