ok, here's the deal. It doesn't do it all the time but it does it more when it is cold, but I get a stumble that isn't confined to a single bump on the tach, but begins around 3200 and can sometimes follow into the 4500-5k range. I recently discovered a vacuum line on the egr tube that goes to the cat just hanging out...and the only nipple I could locate to attach it to was taken by a hose that comes from under my UIM..and the nipple is on the LIM on the back, looks like a valve (port?). I also just changed my o2 sensor recently..maybe its my transmission I was thinking at some level, it only does it through the first two gears and it only seems to do this when its in gear going down the road and not while in neutral. BTW, I checked my ground and it looks fine..
So, I also noticed that my primary front injector has moisture around the base of it (a leak) so that means my UIM is coming off soon, looking to replace the pulsation dampner and maybe blocking off the egr- any suggestions guys?

 

check your secondary injectors for leaks both fuel and vac when you get the UIM off, as well as the primaries while you are at it. I had a similar problem, i replaced grounds, cleaned injectors and replaced vac lines but it ended up being a bad spot in the tps, so check that (mine had a spot where it blew open on the multimeter). hope it helps.

 

thanks, I will check that out..
funny thing is I have 2300 new miles on the thing and it just started doing this..a week after I changed my o2 sensor..
any ideas on where that vacuum line from the split air pipe goes?
thx!

 

search 3800 rpm hesitation/stumble, most likely grounds

 

please read my post-

" BTW, I checked my ground and it looks fine.."

Thanks for your attempt to help, but I am thinking it has something to do with my old vacuum lines, particularly the one that I have no idea where it goes coming from the split-air pipe...or my tranny is giving up- would that cause similar issues?

 

check TPS first. When you say you checked your grounds, does that mean you removed the UIM and cleaned the ground there? Did you install an additonal ground at the ECU. Also check your plugs. I have had cases where I've flooded the car and fouled the plugs out (even though they were low mileage plugs). The car would start but would stumble at random parts in the rev range. To check for fuel leaks, put the key in the on position (engine off) and jumper the fuel pump check connector. It is a yellow two pin connector on the passenger side shock tower area (possibly with some insulation over it). then feel around for leaks. You will probably smell fuel.

Also, the transmission has nothing to do with it. you just happen to have problems under low load conditions (part throttle, low gear). This is indicative to me of your TPS, your plugs, or your grounds. I doubt your vacuum line in question could cause it, but you can go ahead and block off EGR if you don't have to worry about it for an inspection.

 

thanks, that's a good place to start anyhow..
BTW guys, I have begun hearing some funkiness after about 4k, and I hear some rattling in my engine bay at that rpm range- what would I be listening for if there was main bearing damage? Just out of caution...