when i start the car, the idles goes up like it should warming up. when the idle comes back down, the idle goes up and down, up and down. it does this a finally dies!! why does it do this??? when i put it in gear it idles perfect and then after about a minute or so it kindof does it again, and it feels like a big miss. just one miss like a bang. need help!!

 

Check for vacuum leaks. They are typical when surging problems come around. Look at the base of the TBI unit along with all of the lines that come off of the unit itself. Trace them with your finger and make sure they are intact and without cracks. What is the state of tune of your car? How does the car run when it is cold?

 

the motor has 4000 miles on it. it is a 350 with a roller vortech cam and stock heads and manifolds. i had a heads/cam motor and took it out for better gas milage. it never did this before i put the motor in. it is actually the 3rd motor and this is the first time for the weird idle. it did this with the old throttle body and another one that i rebuilt. i put another iac and it still does it. with the old iac it would idle @ 2000 and never come down even with it warmed up. when its cold its fine but when it warms up it runs like that. what is the sensor that has a vacuum coming off that egr??? it also has other vacuum lines off that but the one that goes to the egr broke recently and i need another sensor and dont know what that is. its on the passenger side of intake manifold. i replaced all sensors besides that one because i dont know what it is. the weird idle was doing this prior to me breaking that sensor checking for leaks.

 

I didn't realize you had a heads and cammed 350 under your TBI. Are you running the stock chip? If so there in lies your problem. Your tune is so far off it is not even funny.

 

The sensor on the passenger side intake manifold is the EGR vacuum solenoid. And, Shifty is right. Your car needs a custom chip, bad.

 

no sorry guys. i guess i didnt make that clear. my old setup was a heads and cam. the new one is a 350 with a vortec cam. thats all. stock heads. the old setup with a stock chip ran better than this. this setup searches for an idle, and wont rpm over 3500 rpm under a load. its really agitating. i have all new sensors, distributar, wires cap rotor, msd coil. i put the timing to 2 degrees with the ecm unplugged and then the ecu takes care of the advance. that let the rpm come up a little higher than 3500. but at 0 degrees like the factory says to put it, when it hits 3500, thats IT! it flattens out. people have said the factory exaust is the double layer and the inner layer can collapse adn could cause some or all of the problem??? i have a gutted cat and 3 inch exaust cat back with all fairly new pipe. unless the guy that gutted the cat left particals in there that just now after 2 1/2 years clogged up?? non of this ever happened untill this new motor. im pullin my hair out guys!!
p.s. where can i get the switch your talking about for the egr??

 

You can get an EGR vacuum solenoid at any parts store (if they have it in stock). Sometimes it's hard to find one for some reason. If no auto parts stores have them, go to a junkyard and get one (or more just in case one is defective).

 

You still need chip tuning. You have 45 more cubes and a differnt cam. The parameters of the chip are way off.

 

i have a stock 92 ecu with the 350 chip