I have notice the past few days my car just didnt have the pull it is supposed to. I wasn't sure if this was the case, or if I was just imagining things. This morning, I was driving home from work and started to notice it slightly more, so I tried opening it up doing about 50. Now I could really notice something was wrong. Didn't even throw me in my seat the slightest bit. Took about 3 full seconds to get to 60. I also noticed lately it makes a weird kinda rattling noise when I accelerate when the engine is cold, but it went away when it heated up. It started to do this about the same time I started to notice the power loss a few days ago. Anyway... I figured I would try to open it up again, but this time from a slower speed. As I turn onto my road, I open it up. Barely anything. I felt like I was driving a stock Honda or something. Then it went downhill fast. For a second it was juts really slow, then as the RPM's started to climb, it sounded really nasty. Somehow I could tell the noise was coming from the intake. Almost like you could hear the engine out the intake (CAI). Don't ask how I could tell... It was weird. Anyway... As the revs got higher it never shifted... just stayed in first. It finally hit the rev limiter at 6 grand and stayed there. I looked behind me and there was a decent amount of smoke. Not a HUGE cloud, but I could definitely notice a considerable cloud through my dark tint. Barely made it up my hill to my house. Now it sounded horrible. Like a nasty groaning sound from the intake. Almost like if you were to take the intake (filter) off of a 4 cyl. and drive around. Got it in my driveway and poped the hood. Burped the throttle, sure enough, nasty groan out the intake. Something is definitely wrong. Key points... Slowly got worse over the period of about 3 days. Groaning/deep howling noise out of the intake. No *****. Idles fine, maybe a little rough, but not sure if it is any rougher then normal. Oil level and pressure are good. Doesn't really sound like a miss. Don't think the timing chain slipped because again, it got worse over time. Sorry for the long post, but any ideas?

 

Just took it down the road and back and it is not as bad. This is after it sat in the driveway for about 20 minutes to a half an hour. Later I will drive it more to see if it craps the bed again when it gets hot. BTW, sounds like there is more top end noise, like in the right side lifter bay.

 

What color was the smoke that you saw behind you? Check and make sure your oil level and coolant level is topped off. The smoke you saw out back was possibly unburned fuel. Is the service engine soon light on?

 

SES light never came on and the smoke was def. fuel. I am about 90% sure it has been running rich lately. Maybe plugged cat? O2 sensors wouldnt make it do what it did. I just don't know what the rattling noise was. God, I hope it's not internal.... I'M NOT READY TO TARE INTO HER YET!!!!!

BTW, I put in a new GM opti about a month ago. Also, I'd like to make note that I do have the MSD ignition in it. I hoping the black smoke was caused by the problem, which would lead me to think that it's just running EXTREAMLY rich, or there is an igniton problem. It could also be that it was just held at the rev limiter for a second or so, and running rich, which again it has been, would cause the smoke. Maybe not even connected. I sure hope it is. Maybe one of the O2 senors finally crapped out and it's just dumping fuel???

 

Maybe the noise was piston slap? I would look into the ignition.

 

I think the rattle sounded external. Hmmm... I hope it was anyway. Maybe it's not even connected to the problem. I really don't want it to be, but all this praying and hoping isnt gonna help any.... I need to figure out whats wrong and not just keep hoping.

 

Ok. I went out and drove it around to get it to do it again. After about 20 minutes of beating on it, it finally started to lose power. It started out mildly, then eventually got to the point where I crawled up my hill again. Parked it and opened the hood. Noticed some smoke come from the back of the motor and to the right side of the engine bay (left, as your lookin at the engine). Looked around from where it was coming from. Got underneath and saw that it was coming from the cat heat shield. Looks like the cat is getting very hot. Looks like a plugged cat to me. Would this cause my symptoms? Would it be fine when it's cool but start to run like crap when it got hot? Why else would the cat be getting hot? I put my hand up to the exhaust and didn't smell any fuel or anything. I'm hoping for a plugged cat. If you guys think it is, I will end up just hallowing it out. I have heard this can be done by just droping the pipe after the cat and jamming a crow bar or something similar in there and breaking the cat up. Then just starting it up and reving it up to blow the crap out. Sound like a plan?

 

Well it was a plugged cat. I hallowed it out and took it for a drive. Everything is fine now.

BTW, for anyone wanting to hallow the cat out, everyone is right when they say it sounds like a tin can. I don't like the sound, but for now it's better then a plugged cat.

Oh yeah, the best part about this whole thing was, I hade to drive down the road to get some new flange bolts, and of course, the exhaust wasn't connected .... OMFG!!!! One, I've never heard anything louder, lol. Two, I am definitely puting headers and a cat back on. OMG, it was un unreal ride. I opened her up doin about 10MPH and when it shifted into 2nd, it blew me sideways and nearly off the road!!!!!! WHAT A RUSH!!!! It never even chirped em before. Now with the exhaust connected, it chirps em into 2nd. Must have been a little plugged ever sence I bought her, lol.