Hello Im new to the forums and hope someone can give me another direction to go.
I bought a 32,000 original mile 1987 Z28 the the 305 tunedport motor. The car at idle has a slight surge that is not consistant. At times its fine and others its rough. I have already replaced the fuel filter,factory plugs,wires and cap/rotor. I also change the air filters. I have put almost 8 tanks of fuel thru it and have also used concentrated cleaner in each tank thinking since the car was hardly driven that it may have alot of carbon build up. I have taken it to a chevrolet store and had a corvette specialist go thru it and he can find anything nd says its normal. Thru the exhaust you can hear small pops sometimes. Any info would be appreciated

 

IAM HAVING THE SAME PROBLEM SOMETIMES MY CAR POPS THROUGH THE FRONT OF THE TPI AND OUT THE EXAUST ONLY SOMETIMES ''ITS NOT NORMAL CHECK YOUR FUEL PUMP OUT AND YOUR INJECTORS

 

your exhaust pops when you get off the throttle right? it happens some say it is normal... ever seen pro stock cars. they shoot a 3 foot flame in the turns off the gas that is the good ones of course never get off the gas long enough but are you getting a Check engine light? get the codes from that first if you are it usually wont tell you whats wrong but it will give you a idea

how big of a surge are we talking about 100 rpms or 5-600?

 

The surges are only like maybe 100 rpm. There have been no codes. I did pull the air intake off and I see carbon on the flappers in the throttle body. This car is immaculate showroom condition. Would I be an idiot to take it somewhere and have a bilstein throttle body injector cleaning. They tried to sell this 2 me last time but I think they are a rip off. I have used injector cleaner in every tank of fuel so far and I am lost at this point. The only other thing I can think of is a poss IAC motor??? What do you guys think. thanks for your input

 

yes you can clean the IAC out there is a tech artical on it and how to reset it... might do wonders...

 

I have a similar problem.
Did you ever fix your problem? what was it?

 

Check the EGR for carbon build up and the type of EGR...Some are run by exhaust back pressure and cause idle problems,..which means taking a look at the cat for damage or plugged.
Take a squirt bottle of water, set it to SPRAY or MIST. Rev the engine to 2500 or 3000rpm. squirt the whole bottle{or two) into the intake while holding the rpm's. Take the EGR off, it should be full of carbon now....clean it and reinstall it. Do it over. The hydrogen in the water chemically reacts with the carbon splitting it apart and blowing it out the exhaust and some ends up in the EGR. I've been doing this on all my engines over the years....it keeps them clean.