Sputter / rattling noise when engine on

If it's just briefly on startup and not consistently, it's the nature of the Atkinson engine. But the video is hard to hear and you aren't providing additional information. How is the current MPG? Any warning lights on the dash? When was the last time you had a tune up? Oil change? Any other issues?

 

Sounds to me like you've got some sputtering going on whether that is a miss if it is a miss. It's very consistent or it could be a loose gasket in the muffler system but that's a stretch need to get the car up on ramps and just have a look while the engine's running if you're afraid to do that a muffler shop will lift it up and have a look.

 

The 38 miles per gallon is certainly a giveaway these cars get 40 on a bad day I realize 38 is just 2 mi away but for me to get 39 in any of my generation twos I have to connect my lightweight trailer and it's like the minute I connect the trailer the display changes to 39 mpg like clockwork it seems almost uncanny. Disconnect the trailer and it goes right up to 47.1 generally speaking. Me personally I'd have to be pulling the plugs out looking in my spark plug wheels checking the gaps If not just replacing the plugs I'm not sure about these expensive tune-ups there's really no such thing in this model plugs can be expensive if you want nice original factory guaranteed that sort of thing they can cost you 50-60 bucks in this day and age but other than that there's not much else to tune up I notice in most of these generation twos I work on the spark plugs are literally seated finger tight it's almost unnerving every one of these I work on I dropped my spark plugs extension socket in the hole onto the plug fit my ratchet with one hand and twist with one hand with almost no energy and I'm lefty loosening the plug right out One handed That's not good. Something is going on here and it needs to be checked probably on a lift Not necessarily at the exhaust shop but anybody who'll pick it up and have a look You've got a leak something is happening a constant miss when your foot's on the gas possibly The MAF sensor needs to be cleaned or it is badly built up something.

 

Yes that is correct on it Very old car 2 miles less per gallon than what it shipped doing is pretty normal The car shipped rated at 47.1 by the EPA

 

My 2009 (The Darkstar) was running rough at start up and clearly missing on #3 when cold. (according to the error logs I saw in tech stream: pending errors) I changed the coils, injectors, plugs and things greatly smoothed out. (180K miles I think) Also, you do change your ICE air filter when you change your oil right?

If you think it is really coming from the exhaust, check the rubber mounts near the muffler, maybe they are worn out. You can probably see that visually or if the car is cool, grab the muffler/tailpipe and give it a shake. All the vibration should be "damped" with no hard stops. There are a couple of mounts at each end of the muffler and at the front of the resonator. As I recall all those have rubber in them which might be old and cracked and no longer soft. There is also a bracket towards the front that can get loose or damaged. Crack head thieves who try to steal your cat may damage that bracket if they are not experienced thieves. (I would use a Klingon word for them but this is a family venue.)

Do you smell exhaust anywhere but at the tail pipe? (check just behind the passenger side front wheel for example)

Beyond that I would echo Tmbukt's thoughts on running it on a lift and also checking the cleanliness of MAF sensor. Use cleaner solutions specific to the MAF sensor and follow their directions. And don't drop the sensor as they are fragile.

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