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Discussion Starter · #1 ·
Does anyone know what options there are when replacing the cat on a focus. I know the dealer is wanting 1k for a replacement. I had a chevy that you had an expensive set up but I was able to cut the cats of the manifold and weld some aftermarket ones back on with no issues. Has anyone tried this on a focus?
 

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Vince your Moderator
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Go to a muffler shop and have the make you a cat delete pipe.

Or Google ORP ford focus.

Kill the cat.
 

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Go to a muffler shop and have the make you a cat delete pipe.

Or Google ORP ford focus.

Kill the cat.
That would work great if the catalytic converter wasn't in the exhaust manifold on the 05, but it is.

What are your symptoms? Mileage? Transmission? It could be a snow job, that is very expensive even for a mani-cat. Also, the 05 had welded tubular manifolds, but the 06+ have cast manifolds with 3 O2 sensors compared to the 05's 2 sensors. That might have some effect on dealer prices.

As far as I know, nobody has disassembled the mani-cat on a Focus. It has 2 cats, so also verify which one you're referring to. I assumed the mani-cat since it's so expensive. There is a second cat under the car after the flex pipe. That one would be a simple job- weld in any aftermarket cat.
 

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Discussion Starter · #5 ·
The car is an 05 zx5 with 120K and an auto trans. It was throwing a p0420 bank 1 cat low eff when I posted. I disconnected the battery to do some other work and the check engine went away. Just wanting to know what I can get if I have to replace. Fordparts.com part to replace is 1k.
 

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I don't think that code is for a cat. Like I said- it's possible it's a snow job. Here's the detailed description from our files- which are located in the "Ford Focus Technical Chat Stickied Threads" thread near the top of this forum page.

P0420 - Catalyst System Efficiency Below Threshold (Bank 1) Indicates Bank 1 catalyst system efficiency is below the acceptable threshold
Use of leaded fuel
Damaged HO2S
Malfunctioning ECT
High fuel pressure
Damaged exhaust manifold
Damaged catalytic converter
Oil contamination
Cylinder misfiring
Downstream HO2S wires improperly connected
Damaged exhaust system pipe
Damaged muffler/tailpipe assembly
Retarded spark timing
Compare HO2S upstream and downstream switch rate and amplitude. Under normal closed loop fuel conditions, high efficiency catalysts have oxygen storage which makes the switching frequency of the downstream HO2S very slow and reduces the amplitude of those switches as compared to the upstream HO2S. As catalyst efficiency deteriorates, its ability to store oxygen declines and the downstream HO2S signal begins to switch more rapidly with increase amplitude, approaching the switching rate and amplitude of the upstream HO2S. Once beyond an acceptable limit the DTC is set.
IMO, you have a few things to check first before you assume it's the mani-cat. I would also not consider replacing the O2 sensor unless the mileage on the car is over 100k.

What were your symptoms besides the code?
 

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Discussion Starter · #9 ·
I had looked at that one when I was given the info on the code. Thanks for bringing it up, I was just trying to get out in front of the problem if I have to replace the cat. I think the issue may have been something else other then the cat. It is clear now so I'll have to wait and see. Again thanks for the info. If anyone has an idea of what the "usual" culprits throwing these code let me know.

Yes the car has over 100k. I don't want to just start changing things on the emission system just to see if that was the issue.
 

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I don't believe you can go wrong replacing the upstream, downstream, or both O2 sensors with over 100k miles. Some people have solved that problem by replacing those. We have found the Bosch sensors to be lacking severely, and can only recommend Motorcraft. For a good price, check on RockAuto.com. Also check our "Vendor Deals, Group Buys, and Special Discounts" forum for the Rock Auto discount code thread. That will give you 5%. We also have a dealer who works with us: Tousley Ford in WI. Call and ask for Steve, mention FF, and compare the price.

Misfires could be a problem as well. Sometimes those don't always show up as a DTC or a flashing CEL. The ECU doesn't really recognize it unless it's a continuous misfire for X amount of rpm. Things like bad coil boots could cause that code to pop up. You might want to remove the boots and check those, as well as check the spark plugs for any signs of wear. If you've not replaced your spark plugs- then now is a good time. Plats/irids tend to last less than the 100k miles they are supposed to last. The boots in my car started giving me problems right around 110k miles. Boots/springs can be purchased at most parts stores- or RockAuto. I found a set on RA that was made in the USA- and have been good quality so far as well as cheaper. I can't remember the name, but the low price is what I went for. Boots and springs simply pull off the coils, but you might have to fold the boot over to break it loose from the bottom of the coil. Dielectric grease will prevent future corrosion if you find any. Beware of loose coil plug-ins. I had one with a weak clip that I had to double check to be sure the clip was fastened.

I would start there, and reset the ECU by removing the negative battery terminal for 10 mins or so. This will clear the DTC. Then allow the engine to idle for 5 minutes after it comes out of fast idle. Expect the idle to be around 1k rpm if you have a tach. The ECU will perform an A/F test during the 5 minute period, and you might see fluctuations in the idle. Once it finishes, the idle will drop to normal. If you don't do this- your fuel economy will suffer until the ECU has a chance to perform the test. You'll also experience a lower fast-idle at cold starts until it does the test.

Feel free to ask more questions if needed. IMO- you should start with the simplest/cheapest fixes first.
 

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Discussion Starter · #12 ·
I don't believe you can go wrong replacing the upstream, downstream, or both O2 sensors with over 100k

Feel free to ask more questions if needed. IMO- you should start with the simplest/cheapest fixes first.
Thanks for that info, I'll will start looking into those issues.[wrenchin]
 
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