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so my 88 gt will start fine... when started it goes to about 2grand then comes down and idles like a holy mess... and it sounds like there is a huge air leak on the motor somewhere... i have check the vacuum hoses for leaks and didnt find anything... what could this be.. it has the 2.8 in it....

get some carb cleaner and start spraying around the intake and throttle body to see where it starts to rev up... that's where your vac leak is.

Make sure that the three vac lines (that are joined together to one seal)are in the TB.

they are all together... my buddy said it could be an intake gasket... i don know if its a vac leak or not i will spray some cleaner in there and see...

don't spray it in the intake, spray around the top of the motor, your trying to find the location that its sucking in air where it shouldn't be.

well i sprayed around... didnt find anything...i adjusted the idle screw up alittle to bring the idle up... now it idles fine but when u rev the motor it comes down to about 250 rpm and has a hard time coming back up... and when you drive it, at lights it does the samethings but if you dont stop it is fine.... also the hose that looks like it runs from the rear valve cover to under the intake when i spray around there it revs up alittle... so is it that hose thats doing it...

If you put a huge cam in it would be ok to move the idle stop. You have something wrong and moving that can make more trouble down the road.
The PCV tube must have a hole in it. Get a new PCV too, that way you don't have to change it later.

I would also check the IAC valve, THAT'S the part that controls your idle.. Not the screw.

I don't know how many times I hear about people "adjusting the idle screw" on these cars when they are electronic idle controlled. Its not a carburetor, not the same principal.

well i pulled the intake off and the air tube that runs under the intake was cut pretty bad... so i fixed that and it runs fine... now it just does it after it been runing for a while...but its not to bad.. it runs great ..

Did you put a new PCV valve in?
So the idle is still bad?

no i didnt put the pcv in it... and yes it does after it runs for a while... the motor doesnt knock or leak or burn anything... so is it the pcv valve.. and how would i check that...

Shake it, I'm not joking(if it makes noise it's ok). It shouldn't cause an idle problem though. If it's stuck or sticking all your blow by will build up and blow your gaskets. Just trying to save you some work later by replacing a very cheap part.
Ok, if you can get to your vapor canistor take the two lines off and plug them. If the idle is better then the vapor canistor purge valve is bad. I wouldn't keep it that way for long(just for a test).
Just remember that it's hard for us to tell what's going on by reading text. Don't get mad and give up. Keep posting!

well i unplugged the vapor canister and it didnt do anything... it didnt help or hurt the idle... now the car does have a 3.1 now instead of the 2.8.. the old motor did the samething too.. do you think it could be the computer... also when i unplug the vacuum line running to the sensor on the top part of the firewall it does idle better...

Your MAP sensor? I didn't know it would run without it. I'd say pick up a new one. It gives the computer the ability to make changes to the air/fuel and spark. Oops, you have a MAF don't you? It would be in the intake tube. It has the same ability(it reads the incoming air, not vacuum pressure like the MAP) and would cover most of the loss of info from a bad MAP. I'd still get a new MAP, from the way it sounds that should end your trouble. Be ready...they are not cheap.
I'm sorry man, I forgot about the MAF. I have never had a car with one yet. My first Beretta was a 90GT 3.1 and it didn't have one(in 96 they came back and I now have a 95, missed it by a year). I sometimes have trouble thinking outside of what I have.

Oh and don't forget to put your throttle stop screw back to where it was. You may need to take off the intake tube and watch where the throttle plate is as you move the screw. Make sure that the plate is free to move, touching the bore but not smashed into it. If it's too low it could stick closed. Too open and it will idle high. Keep in mind that the IAC may need to reset after you get the plate back to stock postion. You may have to turn the car off, let it sit for a few seconds and restart.

well the motor is out of a 92 regal.. and i did the thing from beretta speed to change it to where you only need a iat... so i have no maf...