Ok first things first, I have a 94 z28 with a stock lt4 other than CAI. Car runs well with quarter throttle, but when at WOT or sometimes even half the car has a hard time accelerating unless I'm at about 2700 plus rpm. Any ideas on what could cause this?

 

Do you mean that at lower throttle (1200-2000) it just seems to stick there for awhile, then heads up in rpms? Or do you mean your actual speed?

It's completely normal/fine for the car to stay in the low rpmsat half toWOT until you have gained more speed,if you aren't in the right gear. If you get unlucky and the trans won't downshift, it happens. If this is what you mean, go out and watch your actual speed, not your rpms.

This all assumes you drive an automatic. lol.

Also, I may not have explained that very well. I think stig or 95slvr or spectercan give a better explanation of it.

 

sounds like the car is hesitating/losing power, could be a plugged cat or possible the opti is dieing

 

If the car just poops out without misfiring, you may want to check out the cat, and the rest of the exhaust system.

 

just to clarify it is a 6 spd man. and its not like im running like 5th gear and 30 mph and trying to nail it and it struggles, ill be going around 30 in 3rd gear about 2000 rpm and if i floor it the car struggles. I was thinking it was either not getting fuel or I have like Alih said a plugged cat. Also it shouldn't be the opti because it should only have around 30 thousand on it. I was just wondering if anyone else had some ideas on it.
Thanks for the help

 

ok i have finally had the time to take the cat out it was pretty plugged up, helps quite a bit but im still going to go through and check the maf and o2 sensors and hope i dont need to come up with the money for a new opti

 

ok got done cleaning the 02 senors and MAF which had quite a bit of dirt on the screen, care seems to run a lot better but it still is a little hesitant. the strangest thing is it seems fine at WOT and at 1/4 throttle but it still seems a little goofy at 1/2 throttle and at lower rpms, i am thinking i have a timing problem now.
thanks for all of your help guys

 

My car did the same thing and i was ready to buy a new opti but instead i put new O2 sensors in and it runs great. I heard you cant clean them you have to buy new. Not sure if it's the same exact thing as yours but sounds like it. It was like a really bad hesitation i could put my foot to the floor and it wasn't going but once it would hit around 2,200 it would take off.

 

A clogeed cat can damage the O2 sesnsors, and no amount of cleaning is going to help.

 

i know what you mean its like you floor it and it dont want to go. im going 30 and it picks up slow but only sometimes. i have an auto so maybe thats my problem