i am the new proud owner of a 1985 corvette, and the car runs great and drove great on the 200 mile trip home, now i use it very rarely in the winter it stays in the garage covered, my question or concern is the idle, in drive it is about 800 to 900 rpms and when i put it in park it goes up to about 1000 to 1150, when i knock it down it goes to about 750 to 800 rpms, and some times it goes up or down, is this a concern i should be worried about and try to get fixed and should i be knocking the rpms down or should i leave it any and all answers would be helpful thanks again.

 

To me it sounds like you could benefit from taking the time to clean your throttle body and reset the minimum idle. You can find out how to do both pretty quickly with an advanced search. Assuming you have a stock chip, your idle in drive (once warmed up) should come down to around 600 rpm in drive and around 750 in park.

It's not a big deal to do the TB cleaning and minimum idle reset if you don't have concerns working on your own vehicle.

 

Could be a carboned up IAC.

 

could be the butterfly shaft bushings...........spray the bushings with wd40........that will correct it for a short time, and maybe narrow down the problem.

 

with Rick. This is more than likely the cause and the easiest to get to and correct. A little carbon in the plenum will not have the same impact as in the IAC. The pintel (plunger on the IAC) controls the air into the TB at idle. Not likely it is the butterflys, they only have impact when the throttle is opened. Start here by pulling off the throttle body, IAC is under this. I would use some PB Blaster on the screws of the IAC body and let it sit over night. Then open things up and clean it out. Be carefule of the IAC plunger. Use anti-seize on the screws before re-assembling. The reason for the anit-seize is that the IAC body is aluminum and the screws are metal....two different materials. Over time they will bind or if you tighten them two tight they will gall and seize . Do it right and save yourself future problems.

Good Luck and enjoy your 85

 

:o i forget to mention that i am not to good as a saturdauy mechanic, should i let it go until i bring it to my mechanic in the spring thanks again.

 

The only way to get good or better than you are currently is to try. That is the only way to learn, and the more you learn about your car the better you are. Points to remember:
1) Get yourself some form of manual, ether cheap Haynes or spend the $$ and get Helms FSM. - These give you basics, what to do and how, torque etc.....
2) Always label each thing you remove, screws, hoses or electrics. Don't rely on memory...it does things.
3) Label bolts etc and place in bags so you don't loose things or seperate things. IE. the torx bolts that hold the runners to the intake on the 85 are different sizes
4) If in doubt, draw pictures or take pictures (DIGITAL is great).
5) Take your time.
6) Use good tools, there are times that the correct tool will save you hours or skinned knuckles.

That said, you can tackle this job. To remove the TB, first disconnect the neg. battery terminal (black not red). Disconnect ducting from air cleaner to TB. There is hose going to TB on drivers side and exits on passangers side that carries water thru TB, disconnect and think about a TB by pass (do a search). Disconnect all electrical, be careful of the little plastic clips that hold these two connections together...carefully pry open with a small screwdriver while pulling on the connection. Remove other hoses. Unbolt the four bolts holding the TB to the plenum and remove the TB. Remove the ICA from the base of the TB by inscrewing. As I indicated earlier, use PB Blaster on the little bolts on the ICA aluminum body on the underside of the TB and let that soak in over night. Then remove the screws and pull the ICA body apart and use TB or carb cleaner on this and carefully clean out the carbon. Do not scrap the inside of this area, especially the spot where the plunger seats into this section. Use a small brush with the cleaner several times to clean this up. Clean up the TB while it is off, the same way with a little TB cleaner and a brush. Re-assemble.

If you get to a point were you are stuck or have a question...PM me.

-John

 

oNE OF THE FEW WAYS TO LEARN IS TO DO. THIS IS NOT A DIFFICULT JOB. CHANCES ARE THE TB AND IAC ARE "CARBONED UP" mAKE SURE YOU USE INTAKE CLEANER AS OPPOSED TO CARB CLEANER, ESPECIALLY ON THE IAC.

WELCOME