I have changed the spark plug the coil and the fuel injector. Checked the injector it is working. Starts right up rough idle.
Apr 3, 2019 at 1:21 PM
Cylinder seven misfire
2003 MERCURY MARQUIS
KEVIN ELTING
- MEMBER
- 3 POSTS
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SCGRANTURISMO
- ✓ASE Certified Mechanic
- 4,897 POSTS
Hello,
Have you checked the Idle Air Control (IAC) valve? This will cause a rough idle and intermittent misfires. I suspect that this is a 4.6L engine, and if it is any kind of vacuum leak will cause all kind of drivability and idle problems. A good way to check for vacuum leaks is to get a propane torch and being extremely careful turn it to it's lowest setting without igniting it. You just want a trickle of propane "leaking" out of the nozzle. Start your vehicle. Run the torch all along the air intake tract, throttle body, and the intake manifold. When you come across the leak the engine will pick up as it ingests the propane. That is where your leak is. Please check these things out and get back to us with what you find out.
Thanks,
Alex
2CarPros
Have you checked the Idle Air Control (IAC) valve? This will cause a rough idle and intermittent misfires. I suspect that this is a 4.6L engine, and if it is any kind of vacuum leak will cause all kind of drivability and idle problems. A good way to check for vacuum leaks is to get a propane torch and being extremely careful turn it to it's lowest setting without igniting it. You just want a trickle of propane "leaking" out of the nozzle. Start your vehicle. Run the torch all along the air intake tract, throttle body, and the intake manifold. When you come across the leak the engine will pick up as it ingests the propane. That is where your leak is. Please check these things out and get back to us with what you find out.
Thanks,
Alex
2CarPros
Apr 3, 2019 at 3:24 PM
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