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Smelly Exhaust



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I did some major maintenance (90000 miles) in my daughter's 03 Corolla and noticed very smelly, rich exhaust while idling and warming up. It wasn't like this 2 years ago when this was my daily driver. No CEL/MIL and everything works great otherwise. Car not abused and I'm maintaining this like before (= overmaintaining). I Cleaned MAF just in case. Anything else to try?

Double check the plugs - designed for 120K mile service life, but on some cars, they can wear out faster. Mine were worn around 95K miles, could have ecked out a couple thousand more miles, but the plug was starting to show excessive center electrode wear. Can't hurt to check the air filter and seal on the airbox, while you are checking the MAF sensor.

If you notice a strong rich exhaust smell toward the front of the car, or even a raw gasoline smell - I'd double check the injectors - see if they are leaking. Check for exhaust leaks - front pipe is well known to leak on both the 8th and 9th gen Corollas. If the rich exhaust smell is noticed well after the car has warmed up - possible that the O2 sensor is slowly dying or reading lazy. Mileage and age are about right for getting close to the max lifespan on this sensor. If you have access to a datalogger - might be worthwhile to see what the fuel trims look like (LTFT and STFT).

How often is the car getting driven - driving conditions? If the car sees a significantly lower amount of runtime/usage than before - sits for extended periods of time - could result in an overly rich run during idle until it gets to closed loop. Might just need an "Italian tune-up" - a good run on the highway to burn off deposits and get all the fluids up to temp.

Thanks fishexpo for replying. I should have explained more abour recent maintenance. The spark plugs were replaced 10,000 miles ago and inspected 3,000 miles ago. Air filter was recenly changed too. The LTFT is low and close to zero. STFT on the orther hand is close to -10 on start and slowly goes down to somewhere between 0 and -5 after warmup. No bad smell after warmup. No raw gasoline smell or sulfur type of smell. My daughter just came back from a sizable hwy trip and she drives close to 80MPH.

I thought about exhaust leak too because I thought I heard a new ticking/knocking sound. Is it something I can check or should I take it to a mufler shop? Where exactly the leaks like to happen in 9th gen?

There is a ball gasket that sits between the exhaust manifold and front pipe assembly. The OEM exhaust setup is pretty long - front pipe, cats, resonator, piping up to muffler assembly - all one piece. Even with the hangers on there - puts a lot of stress on the spring bolts that hold the front pipe to the exhaust manifold. Also check the top of the pipe - somethings the piping all checks out visually from the bottom - sometimes the metal will completely perforate at the top of the pipe, next to the undercarriage - hard to inspect quickly.