BBryan

I have a 05 Civic Auto. 228k, It's a weak car anyway , but started really slowing down, especially on the highway trying to get up hills. If it shifts down it slows even slower and acts like it's not getting enough fuel. it will hardly pull up a hill. A "blue hair " lady was even trying to pass me ,
I changed the fuel filter and cleaned the screen. I haven't been able to check pressure. Autozone didn't carry a tester. I'm thinking it could be the pressure regulator, but don't wanna keep replacing w/ guess work. Is the regulator a common problem w/ these cars. And if I put on a aftermarket, can I leave the old one hooked up in the tank.?

ezone

CEL on? Got codes?
Exhaust or intake restriction?

P0420 and cat came apart or clogged?

BBryan

The CEL did not come on, I didn't think of exhaust, but it doesn't sound like it restricted. Air filter looks good. Thanks for input

ezone

A restriction on either end won't normally make real noise.....but it makes a whole lot of difference in performance.

Filter may be ok, but is the air breather chamber loaded with dog food or some such? (rodents packing away food is somewhat common in my area)

For exhaust restriction you can check using "vacuum drop method" (google it) but to confirm that test I like to actually open up the exhaust to prove it's the problem:

If you have the cat down under the car (D17A2), disconnect the front exhaust pipe from the manifold and see if performance returns.

If the car has the cat attached to the front of the engine (A1), it's more difficult....Remove the primary O2 sensor and see if you gain a smidgen of performance at wide open throttle.