Engine still lagging/bucking, help! Options

[GriffGirl]

I'm still having weird engine issues. It was bucking really bad until warm up, especially in higher RPMs. I did a tune-up which helped but didn't solve it, engine would still buck while cold at higher RPMs (3000+), and at about 3500+ when warmed up. Fiddled around some more this weekend, resulting in amazing improvement; now instead of bucking, it just kind of feels like it's dragging like a dog scraping its butt on the carpet. Yes, at higher RMPs, and regardless of what gear I'm in. I've done the following thusfar to resolve this issue:

•replaced thermostat
•replaced engine temp sensor
•replaced plugs, cap & rotor, air filter (improvement #1)
•replaced fuel filter
•seafoam gas treatment, seafoam vacuum line (discovered leak in gasket around header pipes)
•removed intake housing, cleaned the hell out of throttle body/plate
•realized that did nothing, REMOVED throttle body, discovered diamond mine in carbon deposits, cleaned thoroughly including all those tiny little vacuum tentacles
•whatever that thing is called (is it just the intake?) that the throttle body is attached to, well I sprayed the HELL out of it and soaked a rag too and did my best to clean it out. It looked like a stalactite cavern. Result was a marked increase in throttle response, made my car feel young again.

But still dragging ass on 3000+ RPMs regardless of gear. What is that thing the throttle body attaches to? Should I attempt to remove the cover from it so I can get rid of the rest of all that carbon build up? Is that my problem? Does anyone have any other ideas? PLEASE?

Thanks...

[Havok1997GT]

Normally if your Cat is clogging like that its because the Catalyst has cracked and broken off in the Cat. If you've ever had a bad Cat, it will sound like something is rattling around in your exost pipe. and you'll hear it just with the little shaking you do when you get into the car. Best way to tell is get on the ground near the Cat and shake the car if you hear rattling id put my money on a bad Cat.

Follow the Spark idea first. and one of the best ways to do this is take the car to someone who has one of those computers they use to check what kind of engine code your pulling when you have a Check Engine Light. Ask them to see if you misfiring. If you are that would be your best bet to your problem. After that its a matter of finding out what's causing the misfire, Spark Plugs, wires, cap,rotor, and so on. Most of these are cheap fixes until you get to distributor and that's when things get up in price. Word of advice, with distributors, should that be the problem, spend the extra money and get it from the Dealer. Most part stores only deal in rebuilt parts. Took me 3 distributors to figure out they all where bad because of that reason.

if your not misfiring, i really don't know how much you need to worry about the vacuum leaks or clogs. I just spent 4 months working on my cars EGR system and i had a engine light on, so if you don't have a engine light on i wouldn't go vacuum problem because if you did have one it would seem to me that you'd also have a Engine light on. normally when you have leaks in the Manifold or a clog you'll get a check engine light because one of the sensors would pick up a problem, or at least that's my experience. but a leak might get past the sensors too, so have a vacuum test done and that should eliminate that.

After that. check exiting Exost. see if you have any leaks in the Exost manifold, see if the Gasket is good, make sure you don't hear any rattling in the Cat,

little thing that you might want to check is make sure the Timing is right,

that's what i would do.

This post has been edited by Havok1997GT: Jan 24, 2008 - 8:57 PM