Contour Enthusiasts Group Archives Forums General Troubleshooting Lumpy idle and bogs down at around 4000rpm

Subject says it all really ...

1996 IL4 Zetec /Std Tranny

New Plugs/Wires
New Fuel Filter
Fuel Pressure is around 38psi (42psi with regultaor disconnected)
No apparent vacuum leaks
IAC cleaned (not checked resistance yet tho)

The idle is a little lumpy almost stalling at times
Under hard acceleration it bogs down around 4000rpm if you use half throttle it seems fine all the way to the redline

Exhaust doesn't seem restricted ,and it just passed a Canadian Emission test any ideas?


Thanks

Welcome. . Clean MAF sensor and test for plugged exhaust.

A good cheap way is to remove the O2 sensors, in this order (and see if the performance improves). Uninstall Bank 2 lower (radiator side) to determine if main cat is plugged, reinstall Bank 2 lower and then uninstall Bank 2 upper (radiator) to determine if Bank 2 precat is plugged, reinstall Bank 2 upper and then uninstall Bank 1 upper (hardest one, close to firewall) to determine if bank 1 precat is plugged. You don't need to mess with bank 1 lower as bank 2 lower will also be a test of that issue too (if it is an issue). Battery needs to be disconnected before uninstalling and installing O2 sensors. Good luck.

He has a Zetec, but I am sure a similar procedure could be followed to diagnose the exhaust. First I have heard of opening the exhaust like that to see if a catalytic is plugged.

Oop! Revised for the Zetec.

A good cheap way to test for a blocked exhaust is to remove the O2 sensors, in this order (and see if the performance improves). Uninstall Lower to determine if main cat is plugged, reinstall lower and then uninstall Upper to determine if precat is plugged. Battery needs to be disconnected before uninstalling and installing O2 sensors. Good luck.