Mark58556

Okay I have a 2004 3.8L mustang, automatic, I've only had her for about maybe 3-4 months now. She's always had a problem with the exhaust. I've replaced the passenger side manifold, replaced the EGR valve, and welded spots on the exhaust cause there were holes. Everything was great after all the new equipment was put in, then three weeks later she started acting up. Either switching from 1st to 2nd gear, or 2nd to 3rd, one of those, she runs up to 3,500 RPMs when usually it would switch gears at 3,000. Idk if that has to do with anything but now she doesn't accelerate fast at all and I have to give it way more gas than usual just for it to get going. It's like she's lost all her power and doesn't have the "umph" anymore. The only thing I've done that would affect the engine performance would be the cold air intake that I installed a month ago. There are no bad side affects that I know of. Also, my gas mileage has been cut down quite a bit. I'm assuming I need to replace the driver side manifold? Btw the exhaust is all stock. So yeah that's what I'm assuming what needs to be done but I don't wanna spend $300 to fix something that's not even the problem. Thanks

Daehawk

Almost sounds like you have a clogged CAT or two. Bad mileage and loss of power are symptoms. Maybe the holes would allowing a good flow and once sealed up the CAT is blocking it now.

jwog666

^^^^^^, this, have a shop check the backpressure, or remove the exhaust from the manifold and take it for a ride, if the symptoms go away, you can assume the cat is plugged

Mark58556

Ah thanks guys. Just dropped my car off at the shop 5 mins ago and they're gonna check everything. They said either the cats or a bad fuel filter.

Mark58556

Ah well just got a call from the shop and they said the cats were fine. The only other thing they said could be off would be the fuel filter and that could cause these symptoms?

Daehawk

Well at least if its the filter it should be a lot cheaper