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Cat Converter Plugged On 1.8L ?

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#1 morganism



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Posted 04 March 2016 - 07:24 PM

Just replaced the upstream O2 last summer, now downstream failing.


Can't go over 45 uphill, downshift causes bogging.


idle exhaust is not very forcefull, but it is a 4 cyl...


No whif of oil or gas in radiator.

No trouble filling tank, tho a bit of gas smell when starting.

oil burning is going down a couple oz,s a month, since we started changing it less. No choclate milk there....

Water resivoior not dropping noticebly, even in desert sw.

200k miles, but not a lot of long trips on this vehicle. Big altitude gains/losses as daily driver. 3500 to 5000 ft a day.

Dealer charged us a 1k last year trying to fix. No fix. i replaced O2 , ran pretty good till now...


2001 le, 1.8l


I understand there is a computer/software bug in these cars, and there is a big downhill coast/engine brake happening in afternoon after starting, which would increase rich fuel loading, but am suspecting Cat now...

#2 morganism



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Posted 05 March 2016 - 03:52 PM

Just checked records.


Dealership changed O2, AFM, plugs, wires, injectors, coilpacks, All in the last year, problem not fixed.


nearly 4k, and still havnt found the prob. Ouch.

#3 fishexpo101


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Posted 08 March 2016 - 12:09 PM

Possible it is a clogged cat - backpressure test with a probe or if you notice a considerable amount of blowby, then that could be the case.


But it takes a LOT to clog a catalytic converter.  Exhaust leaks can also cause the ECM to misread O2 values, causing the engine to run too lean or too rich - which will affect power.


Not completely understanding what the dealership changed or why:  O2 sensor (upstream), plugs, injectors, coilpacks - I can see as possible culprits, hopefully they gave you the old parts back.  Wires?  What wires - spark plug wires?  I hope not, your car doesn't have plug wires.  AFM? Not on a Corolla - maybe a BWM or similar.  Unless they meant the MAF sensor - those can be cleaned, don't have to replace them.


I'm surprised they didn't check the VVT-i system - as that would cause a lot of headaches if it wasn't running as it should.  If the valve overlap is not right with the VVT-i, could get stumbling, low power, bogging at high speeds, etc. 


Transaxle issues are another possibility - especially if the car works OK, just doesn't want to get up past a certain speed.  This would also point to that funny downhill engine braking you are seeing, should be doing that unless the fluids are too cold.  Could be a bad shift solenoid or transaxle.