My car has been running rough lately. It seams very down on power in the low rpm range and it takes a long time to rev up to redline, much longer than it used to. It like driving a different car, the power is so low off idle I almost stall it when leaving a stop sign. Also, I walked around the car while it was ideling today and the exhaust tips were shaking, they dont usually do that. My thoughts are that it is the catalytic converter going bad, or maybe O2 sensors.

Car has approx 110k miles on it

New between 104k and 109k

Opti spark
waterpump
fuel filter
plugs
wires

Still original: 110k miles

coil
catalytic converter
O2 sensors and just about every other sensor

I do NOT have access to a scanner, but have no SES light. I really dont want to throw parts at it, but without a scanner I realize I may have to do so, just trying to narrow it down some. Thanks a lot guys.

 

Seems like you've narrowed it down pretty good. Original O2's are probably the problem. I would start there first.

 

Sounds like the symptoms when my cat was clogged. You're due for O2 sensors but I don't think they would cause you to be that far down on power. Old O2 sensors cause you to run rich. I'd also get it scanned for knock to see if the PCM is pulling timing.

 

When is it a good idea to replace the O2 sensors?

 

I don't think there is really a specific time for replacement. Most people replace them when they are having issues with their car. Usually you will get a code if they go bad. I would say though, if you are over 100K and are doing some maintennance, like plugs wires and that fun stuff, I would replace them just for preventitive measures.

 

Ok, I ordered a carsound cat off ebay today. Is there any certain brand of O2's to buy?

 

Stick to delcos. I have bosch and I don't care for them. I'm going to switch back. Car runs better with the delco's.

 

"I'd also get it scanned for knock to see if the PCM is pulling timing."

What would it mean if the PCM was pulling timing? I do have an LT4 knock module so there shouldnt be any false knock.

 

The LT4 module helps with false knock, but doesn't necessarily take care of all the false knock. I ended up wiring up a knock sensor bypass switch to get rid of all my false knock. You want to be sure it's false knock before bypassing the knock sensor!

You may have true knock pulling timing. Scanning the car will show you what the PCM is doing regarding potential knock and timing retard.