2003 Toyota Celica GT Exhaust and Electrical problems.

I have a 2003 Toyota Celica GT, 1.8L manual drive with two unrelated problems, but I didn't want to start two repair threads for the same car.

EXHAUST: The shop I took my car to said I need a new cat, due to a catalyst efficiency code. Their shop works with mine pretty frequently, and they're aware I have access to a welder while they don't, so they advised me to go about replacing that myself to save myself some money.

The question I have, is what do I put in there? I live in a non-emissions county in the state of Georgia, so there aren't any actual laws about what I HAVE to replace it with. (I could cut it off completely and it would still be legal. I wont, because that would annoy absolutely everybody, including myself.) However, I have a pretty far daily commute, and I would like to keep decent fuel efficiency as well as getting rid of that pesky CEL. Loud is NOT my goal, so I don't know where to even begin looking for a new cat in the aftermarket world. As for OEM, I've only found full exhausts available, and at $1800 USD, I would like to try shopping around first.


ELECTRICAL: I have a radio/speaker whine at low volumes. The battery and alternator both tested fine, and the head unit itself is grounded through the antenna which was also found to be good. No whine was heard with the stock radio, and the particular unit I installed was a cheap no-name brand I found on amazon just so I could have bluetooth. I plan on upgrading to an Android Auto compatible radio soon, and was wondering if there's anything more I could check while I'm in there or if the cheap unit could be the culprit?

Thanks in advance!

I'll discuss the Cat issue. The questions I have;

1. What killed the Cat?
2. What Evidence did your "shop" give you to prove the CAT is indeed bad?
3. Was there a backpressure problem?
4. Did they use a Gas Analyzer?
5. Are they basing the diagnosis on Oxygen Sensor Switching Rates?
6. Did they perform an oxygen storage test on the converter, if so, how did they perform this test.

Catalytic Converters are designed for the life of a vehicle, for them to fail means what's in the exhaust stream is killing the effectiveness of the Cat media in its ability to reduce gas emissions.

It's very important to diagnose to the best of our ability to determine what killed the Cat in the first place. Otherwise, the same Codes will come up again.

Here are some very common catalyst killers:

1. Engine Mechanical Issues
2. Misfires
3. Exhaust Leaks and Damage
4. Oxygen sensors; ie. falsely reporting. ie. a lean Pre O2. ie heater issues
5. Over Fuel Pressure, leaky Injectors (Fuel Trims)
6. Very slow coolant leaks into the combustion chamber
7. Oil Contamination
8. Engine Coolant Sensor slow to respond
9. Intake Leaks
10. Ignition Timing

If any of the above issues exist, the new cat will not survive and you'll be back to square one again.

This is a very overlooked problem by many shops in determining if a catalyst is faulty, proper diagnosis isn't done and the customer ends up coming back some time down the road.

I apologize if this comes off rant-ish, but my experience with that shop was not a great one.

There were other codes in the car and all EVAP related; PCV + hose, purge valve, and charcoal canister were found to be the problem. Everything but the canister was replaced. (Charcoal canister is being replaced tomorrow, due to parts availability.) As far as the EVAP codes, I diagnosed them at my shop first, but didn't have time to repair them myself, which is why I had the other shop do their diag and repairs for the same codes.

As for how they diagnosed the cat, I have no idea. I personally have my doubts that a diagnosis was even made considering it took four phone calls for the writer to remember my original appointment was made for a "CEL and oil change." And then I wasn't told the Catalyst Efficiency code was due to the cat failing until they called to tell me my car was done. (They did well with my Tundra in the past, I blame their new writer for the mistakes this time.)

From what I diagnosed myself, there are no exhaust leaks, the PCV had been bad for almost 2K miles, O2 and coolant sensors reporting normally, intake is leak free, the only thing I'm unsure of is any injector issues. I did, however, have a single coil fail 500-ish miles ago and had to drive it home like that. So excessive fuel is absolutely a probability.

I suspect the O2 sensor(s), my boss says just replace the cat myself, and the cat efficiency code didn't return for another 600 miles after their shop cleared it.

Not Rant-ish at all.

Is everything upstream of the CAT good?

Do the Oxygen Sensors respond properly to Lean Condition or a Rich Condition?

Is the purge valve sealing properly?

How are the Fuel trims at all engine speeds under load? The vehicle is older so I would expect to see 12% Total Trim (LTFT+STFT).

If the post O2 sensor is switching continuously when warmed up, and the above conditions are good, really points to a Bad Kitty Cat.

Here is some good info when only a scan tool is available: