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Replacing my catalytic converter

12K views 18 replies 7 participants last post by  tmittelstaedt 
#1 ·
I need help figuring out how to properly buy a catalytic converter for my 2000 ZX3. My engine light is on and I am getting code P0422, and unfortunately the cat is the most likely culprit. I also have error P0455, but I don't think that is causing the cat to give that error, but I mention it just incase it may.

Anyways, I have done some research and found out it'll cost between $500 to $1400 to get that fixed (odds are the larger range). I have searched for cats online, and have seen stuff ranging from $100 to $300. I would rather do it myself to save money. Problem is I need to make sure it will make the engine light turn off and make sure the cat works well enough to get me to my internship as well as pass inspection. Hopefully someone can help me figure it out. I believe my cars engine is a 2.0L I4 SOHC 8V FI Engine. I really appreciate any advice and help in the matter!
 
#2 ·
For starters, the ZX3 was only ever fitted with the 2.0 liter DOHC (Double Overhead Cam) engine. The SOHC engine type you've quoted is not the correct one.
New catalysts are expensive due to the materials that go into making them. Finding a used one at the junkyard may be a better bet if cost is an issue as 1) you're ensured a correct fit and 2) cost will be considerably less than a new one.
Catalysts can be diffcult to remove if you have only a basic tool set. You need to remove the upstream 02 sensor (requires a special socket) and undo a large EGR tube nut. Rusty fasteners through out can also be problematic.
 
#5 ·
Before swapping the cat out, replace BOTH the upstream and downstream O2 sensors with new sensors and see if the check engine light goes away. it will cost about $100 for 2 bosch sensors from the parts place but you may just have a bad sensor. This is a DIY project you just need a O2 socket, a socket wrench, and a jack and jackstands.

And, if this does not fix it then if you buy a brand new cat to replace it, you will find the small print requires that you replace all O2 sensors when you replace the cat or the manufacturer will not warranty it, so it's not money down the rathole.

Where I live every cat that comes into a wrecker goes straight to the metal recycler, you can't find used ones that way.
 
#7 ·
jetrinka, I bought a used 2001 Focus SE back in December that was giving me that code and replacing both O2 sensors fixed the problem. I bought it knowing that code was set and assuming I would have to replace the cat, so it was a nice Christmans present from the auto gods i guess.

I know what the theory says but this is one area where practice differ in how Ford implemented it. In fact when I went to buy the sensor I had the OReilly parts manager confirm the code read with their scan tool (since I use a cheap $9.99 Chinese USB-to-laptop OBD scanner) and the parts guy said that usually only changing the front sensor was needed to fix that problem. I did both because I figured if one was bad the other was at the old rage stage also.
 
#8 ·
Thanks for the link! I do have one concern though. I read in a few different places that using an after market cat could potentially not make the check engine light go off? Another issue would be fitting it in my specific model. At least the second part was explained to me at a ford dealership. Your thoughts or advice?
 
#9 ·
http://www.lkqcorp.com/search-inventory.aspx

Link from an online parts catalog at a local auto wrecker - they have 4 used Ford ones in inventory. Probable cost is under $100. They warranty and ship around the country.

350668553163 Ebay part number for aftermarket converter, complete setup, pipe, etc. Bolt in. 60 day warranty. $180. 99.2% positive feedback.

JC Whitney - Eastern Direct Fit converter - $270. warrantied.

The remove and replace of the converter is extremely easy - tools needed - breaker bar, socket set, socket extensions, jack and jackstands, Never Seize O2 sensor socket

Parts needed:

converter
gaskets (from ford)


open hood, remove 4 bolts and remove exhaust heatshield. Remove O2 sensor. remove 3 nuts on studs.

Raise car, remove bottom o2 sensor, remove converter retainer, remove converter to exhaust line bolts and remove brackets, lower converter and remove, install new converter, retighten all bolts install O2, lower car, install top O2, install nuts install heat shield.

This is like an hour project if you have all the parts ready and the tools ready.

With an aftermarket converter let's say $300 from a local shop, 2 O2 sensors, $100, gaskets & misc shop supplies, $50, labor $50. $500 is about right. If a shop does it they will warranty that it does not work.

With you doing it from a Ford wrecking yard converter - maybe $100-$150 With you using some guy from Craigslist who moonlights auto repairs and a wrecking yard converter - $200-$250.

Since your convinced it's the converter and aren't willing to try changing out the O2 sensors like I said to do, you might as well use a wrecking yard converter from a local wrecker since your going to be putting it in and taking it out to return for another one about 2-3 times before you look at the O2 sensors. That will be a Ford converter so you won't have to worry that it won't fix the CEL.

All these cars use the same converter so they are plentiful in the wrecking yards. The yards only inventory catcons from wrecks where the engine will start and the CEL is not set.
 
#10 ·
Its not that I didn't listen to you haha. I went to a ford dealership and they told me I have to change it. But there was also an evap leak. I didn't have the money for a $1200 converter, so I told them to just fix the evap. They have, and so far, the engine light has been off. I am crossing my fingers that was actually causing the o2 sensors to go crazy. Come inspection time, which is in a month, I must change it if I fail due to the cat actually needing to be replaced. Hence why I ask. But I havent made any commitments to replace it until inspection if it even needs to be changed. Just asking the question because of issues with aftermarket parts and some cars. Since we got experienced ford focus people here, I figure the question is good here.
 
#11 ·
Hmmm....I suspect that either one of 2 things happened. Either when they were fixing the evap system the mechanic discovered one of the O2 sensors was unplugged or the sensor was just loose and tightened it, or when they cleared codes, it erased both codes and whatever is setting the P0422 code is only doing it intermittently. In which case if you have emissions inspection next month you might be able to slide through. If the light goes on again just go to an auto parts store and ask them to clear the codes and see if the light stays off for a while.
 
#12 ·
Hmm, are they suppose to clear the codes? If it matters, the lady at the desk told me that the engine light would still be on, but its not. I am not sure if she meant it will eventually come on again. I hope it was a loose o2 sensor though because I saw the mechanic wiggle, disconnect, and reconnect the upstream o2 sensor. But I appreciate your advice a lot!
 
#13 ·
they need to clear the codes to make sure the evap code does not come back.

if you did not tell them to fix the catcon code then they won't admit to fixing it because they do not want to warranty the work. But, if the mechanic is in there fixing something else and he happens to see a quick 1 minute fix like replacing a connector that got unplugged, most of them will do it and then just not record anywhere that they did it. That way, if the quick fix didn't fix anything the customer doesen't know the difference, and if it did fix something then the customer is going to be happy. (and if it breaks a week later again, then the customer won't want it fixed for free)
 
#15 ·
Cats do not just go bad. People kill em with bad gas and additives. Pull the o2 sensors out and clean the thermocouples(can) around it with emeory cloth. Thread em back in with never sieze , reset you code light and put a bottle of Sea Foam or a pint of Colemans Camp Fuel to the gas tank. I doubt the cat. is bad. Drive it like you stole it . All's will be well again.
 
#16 ·
If the emery cloth thing does not work and your really hard up for cash then try replacing just the front O2 sensor first and give it some time. The theory is that if the front O2 sensor is bad then your exhaust mixture will be wrong and the cat won't reach operating temperature, thus the downstream o2 might get sooted up. When the upstream O2 is working then the cat is likely going to be working, it will be at operating temp, and that may "clean" the downstream o2.

Also in the cheap fix dept. make sure that the gasket upstream of the cat is not leaking. There's a big gasket on the flange that has 3 bolts that hold it together, right above the cat.

But yes, in my case I was getting that code and I replaced both sensors. That was 3 months ago and it's still working fine. But of course I was planning on replacing the cat if I had to.

Don't you have a pick-and-pull wrecker nearby?

Also one other thing - no insult intended here - but many if not most states have emissions repair programs for low income residents. If your on unemployment or something like that, then contact the state as you may get a voucher or some such to get the thing repaired.

Good luck and let us know how it works out.
 
#17 ·
Thanks for the advice. And no offense taken. I'm a student and am about to graduate. So technically unemployed, yes. I will let you know how it goes. I actually ordered a Magnaflow direct-fit converter for $233. Price was within my budget and I hope its not just the o2 sensors. Though everything is pointing to the converter, so I am just gonna replace it. Again I appreciate your advice and time! :D
 
#18 ·
Hi. I don't mean to jack your thread, but I just wanted to share this:
- http://www.obd-codes.com/p0420

There are about 10 different listed possible culprits for triggering that error (P0420).
My own vehicle is apparently emitting that DTC. Along with P0455 and P0457 (false positive).

I believe in my own vehicle, that it may very well be the temperature sensor causing it.
It (the gauge) behaves very funny. Unless it's being accurate about the temperature fluctuating greatly (bad pressure cap affecting the boiling point?).

Before you even bother replacing it: Try cleaning it! Yes. I understand how foolish that may sound. But what is a potential $2 solution?
If at best, it truly is an old wives tale, and nothing but snake oil: It is $2. If it works: That is a $2 solution!
You can try removing the catalytic converter from the vehicle, and letting it soak in either laundry detergent or lacquer thinner. Let it soak in a bucket 24+ hours minimum (completely submerged).

If I'm not mistaken: It could also be the thermostat malfunctioning, which would be affecting the coolant's temperature, which would be affecting the O2 sensors.
After a moment of Googling, I found this from some forum, "14. If the thermostat open just a bit too soon, and the engine never quite reaches operating temp, the ECM will continue to provide a little bit of enrichment. Meanwhile on the other side of the ECM the O2 is reporting a rich condition. If this goes on for too long it may be recorded as a mixture code that may interpreted as a bad O2."

In short: Instead of randomly replacing parts: You should try to really diagnose the problem first.
You can use a multimeter to check the O2 sensors (http://www.ehow.com/how_4870344_do-voltage-test-oxygen-sensor.html).

You can test the thermostat by dumping it in a pot of boiling water (use a thermometer to check the water's temperature first).

You can test the engine temperature sensor with a multimeter (http://www.youtube.com/watch?v=wFHWpgHMAvY or this: http://www.youtube.com/watch?v=G7pE7DQBSV8).

You can test a whole array of things with just a simple multimeter, and basic knowledge. That should really narrow it down and pin-point it to BEING the catalytic converter.

But back on that subject (replacing the catalytic converter): I have a 2001 Ford Focus ZX3 MTX-75.

The only real question I have is regarding the 'hangers' or 'shock absorbers' or 'rubber grommets' that hold up the pipes (and catalytic converter).
How are you supposed to properly uninstall, and reinstall those? I haven't spent much time researching it.
 
#19 ·
Testing a cat in these cars is very simple. You replace both O2 sensors and if the CEL does not go off after 4 full drive cycles the cat is bad.

The fact is though that unless you put an automotive scantool on the car you don't know what your doing. A scan tool will give you readouts from both O2 sensors and comparing those readouts will tell you if the cat is bad or not - assuming that is, that the sensors are both OK.

Washing the cat only worked with old style cats that had metal foil substrate and "ball" style catalytic converters (metal can filled with ceramic or stainless steel balls with a specially coated surface). A mix of detergent (as a wetting agent) and citrus cleaner (loosens carbon but does not harm platinum) was used.

That does not work on the modern cats which use a different construction.

There is a tool for the rubber hangars, just get it from an auto parts store.
 
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