06 Freestar LTD - Ran fine, had plugs/wires replaced, now P0420 DTC - Ford Forums

jcasaccio · 11-01-2009, 07:00

Hi

Just had my plugs and wires replaced as part of 60k maintenance. Went to Midas. They had a really hard time with this, kept getting misfire issues. Finally had it resolved, but the 2nd drive of the car tripped the Engine Service light. I went to the local auto parts store to have them ck the codes and it's a P0420 - Cat efficiency low on bank 1.

I know the Midas folks said they had a lot of misfire issues once they changed the plugs, and kept trying to fix it -finally was a bad new plug in #3 cylinder. I researched this code and found misfire can cause damage to the cat converter. Any other ideas of what changing plugs and wires would do to cause this code? The Midas experience was kind of annoying - took much longer than planned for them to do this and they had many issues.

Said they had to drop engine cradle to get to plugs - could they have damaged the exhaust system in doing so - leaky exhaust can also give this cde - from what I have read.

Thoughts?

Thanks
JC

**rtg143** · 11-01-2009, 13:32

See if this helps. P0420 Error Code: Catalyst System Efficiency Below Threshold (Bank 1)