Join the community and post your question. Use our Ask-A-Tech for free now! ASE experts standing by.

Forum > Failed Smog Test > Question

Check Engine Light Trouble Code P0305 Ford Crown Victoria Misfire

I have a 1999 Ford Crown Victoria Police Interceptor. It failed the smog test because the check engine light was on. The trouble code that it gave is P0305 Cylinder 5 Misfire. My question is what do I need to do or fix to clear the trouble code?

Answer:

If your Ford Crown Victoria does not have any engine symptoms the simplest thing to do is to reset the check engine light and drive your Crown Vic to see if the light turns on again (and P0305 appears). If trouble code P0305 does not re-appear, go ahead and drive for 200-300 miles (over the course of a week) and get a smog check retest. If the check engine light does turn on again after the reset then we have a problem. You want to first inspect the ignition system. Try swapping the number 5 cylinder coil-on-plug (COP) with one from another cylinder to see if the problem now switches over to the cylinder on which you placed the number 5 COP. If you now notice the misfire has moved, we've isolated the problem to the COP and replacing the unit should fix your problem. If it's found that the COP is fine and the problem is something else, we'd recommend checking cracks or hairline fractures on the intake manifold near cylinder 5. A crack will cause an intake vacuum leak and might result in a cylinder misfire. You should also conduct a engine compression test to make sure all cylinders have equal and adequate cylinder compression. posted by SmogTips Support

Related questions and answers you might find useful:

How Do I Get a Smog Check Waiver? by Margaret

Do I Need a Smog Check This Year? by Joy

Mini Cooper DMV Registration Due in 5 Day Won't Pass Smog by anne

2001 Jeep Grand Cherokee Laredo with K&N Air Filter by David

1995 BMW M3 Gross Polluter High HC & NO @ 15MPH by Jared

View SmogTips.com in: Desktop / Mobile