Plugged CAT

Ive got an '05 Legacy GT and seem to be having some issues on the lower end of acceleration. It bogs down and doesn't seem to have any power. It will stumble and kind of chug and then take off out of nowhere. Ive done tests all around but checking the catalytic converter. a few of my mechanic buddies seem to think that ive got a plugged cat. On hard acceleration sometimes when it does take off i do get a weird smell so thats what im thinking it might be. I was told to drive it hard at night for about 10 miles and check underneath to see if i could see the cat glowing. PLEASE HELP ME FIGURE THIS OUT! Thanks!

is the "chug" only happening between ~2000-2800 rpm? If so, could just be the famous fueling stumble that these cars have. Try rolling gently on the throttle through that RPM band.

If you have a plugged cat, it will be plugged, and you will most likely not be able to drive above 35 - 40 mph.

As BMB mention, let us know actally at what RPM range this starts to happen.

Alright thanks i will let you know as soon as i can. But just by rolling on the throttle it does seem to be better but still has the feel of the "chug chug" going on. Then as soon as i get pissed i put it to the floor and it dies right out then will chug and take off!

Your best option is to post a data log to see what is going on, it could be a simple as a vacuum hose being disconnected. Have you checked all the vacuum hoses, especially the blue "T" under the intercooler? Have you tighten down all the intake hoses (at turbo & at intake manifold) ?

I have not but wouldn't that throw a code? When i first bought the car I had issues where they told me it blew a hose off the turbo and my check engine light came on and the car would hardly idle and die out occasionally. But my motor has been rebuilt since then.

Sometimes it will throw a code depending on the hose, sometimes not. Even a bad O2 (air/fuel) sensor will cause a lot of problems without throwing a code. The first thing to do is always check all the connects, since this is the easiest and cheapest route.

The second thing to do is make sure the MAF sensor is clean. Have you ever cleaned it ?

Make sure the battery terminals are clean and tight.

I highly doubt you have a clogged cat.

Where do you live ? May be we can recommend someone to help you.

I have cleaned the MAF recently. Made a difference for a little bit then right back to it. Today it bogged from just under 2k rpm right up to 3k. I dropped it into second gear going up hill and had it to the floor and i literally felt like i had the biggest pos on the road. i wasnt even doing 25mph. I live in Vermont.

My other thought is that it might also be the fuel filter/pump maybe? i know they are in the gas tank in the '05 models so they are a pain to get to but it does seem to get worse with the less fuel i have in the car. Any thoughts on that?

I would think you would throw a cel if it was fueling--car would be leaning out. Can you pull a learning view? Would need to find someone local with a laptop and vagcom cable.

You have the famous 2 - 3k rpm stumble that most of us have encounter. The 3 most common fixes:

1) Replace A/F ratio O2sensor. These are know to go bad without a CEL.
2) Replace the stock fuel regulator with an STI regulator.
3) Do some data logging to see if you need the A/F tables corrected. Contact a tunner.

Once again, these are the most common ones, it may or may not fix your issues.

It ended up being the sensor in the front that regulates how much fuel to put in and also i had a vacuum hose that was pinched. RUNS LIKE A TOP!!