so ive had this, i wouldnt say problem, for while. when its cold i hear like a pulsing sound from the exhaust. almost sounds like the engine is backfiring but a low sounding pulse. i have a test pipe, stealth exhaust. anyways anyone notice this? and is it nromal? like i said it only happens in the morning when its cold.

 

probably just the higher idle so that the car warms up faster

 

I hear a low thumping sound from the exhaust when my car is warming up in colder weather. I noticed it from inside the house while the car was warming up in the garage. I thought it was the subwoofer I was hearing, but when I got in the car the radio wasn't on. I'm not sure if this is the same noise you're referring to, as mine sounds like a low backfiring noise too.

 

mine too

 

Mine does this also, but I think it's totally normal. It's probably just the rich air fuel ratios that are used during the warm up that cause slight backfires or something. Nothing to worry about.

 

Mine does the same thing, but also while i'm under hard acceleration in the upper rpms. No one seems to know anthing about this, its really irritating. Mitsu said they don't know either. Anyone got any ideas? It sounds like back fires but it does it very fast and very consistent. Sounds like a friggen subaru, but the car stil pulls and boost doent fall off.

 

i think its normal. mine does it too like sti said its just pig rich.