JPSilvaggio

I am new to this forum so first I will introduce myself. My name is John P. Silvaggio I am 24 years old and work in Rhode Island as a State Constable.



So here is a list of what is happening:


When I start the car : she will idle at 400 RPMs sounding like she is about to stall then jacks up to 800rpms slowly dropping to 400 and then the process repeats. (i let her sit with fuel injector cleaner in gas tank for 20 minues without 1 stall)

When on highway: I can let go of the gas and the car will continue at roughly the same speed without any pressure on the gas peddle. The only way to get her to decrease the RPMs is to jab the gas, she will then decrease RPMs slightly and then continue at the same speed until I jab again. (The steps seem to always be at 2100->1800->1400)

At red-light: I need to Jab, Jab, and Jab the gas to get her to reduce the RPMs to 800 before breaking so I do not have to wrestle with her.

When Parking: The RPMs while in drive may be around 900. Once I put the car in park they will raise to 1400 and I have to jab the gas once to get her back to the 400->800 almost stall cycle. If I firmly press the gas peddle 1/2 way to floor and let go she will again idle at 1400RPMs until I jab the gas again.



My automotive knowledge/terms are surely lacking but that is the best description of the symptoms occurring I can give. I would appreciate anyone's input.

After everyone's input, I cleaned the throttle body and fixed the above problem.

Problem Solved!

After a needed thorough cleaning, I reattached the throttle body to the plenum and noticed instant results. See below for before and after photos.


BEFORE:



AFTER:




President
John P Silvaggio
JP Silvaggio & Associates
Rhode Island State Constable, Private Detective / Investigator, Firearms Instructor

thecatmac

Take air intake off that is connected to the throttle body and inspect inside. I had an air foil in there that was loose and it would sometimes keep the throttle body open. Also when air intake is off, start engine and manually give it gas and inspect if throttle body closes correctly. You may have a sticky gas linkage that needs to be replaced. Don't mess around with this, find the problem and replace it before you get killed................

greenpigs

If you can't figure it out take it to a shop you trust and get it fixed, before you drive it again.

Muffin

What Catmac said. Actually you don't need to start the car. Remove the black bellows pipe, screw clamp on the big end, two snap clamps on the small end. Remove the electrical connector and set the pipe aside. Be very careful doing this the electrical component is your Mass Air Flow sensor, Both critical to proper engine operation and it isn't cheap to replace. Now you can see the two throttle plates in the air intake (plenum). Plates should open and close freely with no binding drag or "hard spots". Note the spring that closes the plates. If there is any sticking I suggest spraying WD40 or similar on all moving parts and open and close until binding is gone. If it doesn't go away call your mechanic. Don't drive it. As an added thought, the small stranded cable links the throttle plates with the gas pedal. It can easily be removed and checked for freedom of movement. Sorry if my "Dick and Jane"explanation are below your automotive skill level but you are on dangerous ground driving with a sticking throttle.

Midnight 85

Since you don't want help from Moe, Larry, or Curly, please ignore my avatar,
I would do as suggested above and when you get the black bellows-looking thing off lubricate all the pivot points in the throttle body. The area around the shaft especially. I would start with PB Blaster to get things moving freely then a liquid graphite spray to keep things freed up. Also, check the throttle cable to be absolutely sure there is no binding there. As a final note, if you are still having issues then I would check the accelerator pedal itself for freedom of movement. I'm willing to bet you will find the problem somewhere in what I've mentioned.

thecatmac

If you spray it up but it sticks a little bit, replace the linkage.......it's not hard....don't risk your's or someone else's life. You get that thing stuck at +3,000 rpm, the brakes won't stop you. Best thing to do if that ever happens.......turn key off..............

corvettedan22

I agree that you should be able to fic this by checking out the throttle body.

JPSilvaggio

Wow, so many people willing to help! Thank you all very much for the reply's. Although, I do not understand what parts everyone is referring to so I am going to purchase the shop manual.

C4boy

Welcome John. If you get stuck or can't figure it out, drop me a message. I'm about 10 mins away.

corvettedan22

Pop the hood. Have some one hit the gas on and off. Find the part that is moving on the motor. Its either stuck out side or has to be removed and fixed on the inside.

ccrazor

Welcome to the forum.. Once you have the manual it should be a lot clearer..

JPSilvaggio

Thank you for all your support, I have ordered the 1985 shop manual. I can't wait to have it fixed and get her back on the road before the snow comes. Hopefully i will be able to fix this myself.

p.s. what should the engine's RPMs idle at while parked? 800rpm?

AGENT 86

It does sound like a sticky throttle body or linkage/cable.
Disconnect the cable at throttle body and rotate throttle arm to see if it moves freely and doesn't stick anywhere. The drivers side of throttle shaft bore may be elongated form years of use. The result can be binding of the throttle blades in the bore and possible vacuum leak at shaft/bore.
Check the cable and gas pedal for binding, also.
Here is a section from the service manual. There are some pics and info that will get you familiar with what everyone is saying.
http://members.shaw.ca/corvette86/Fu...l%20System.pdf

Cleaning the throttle body and re-setting minimum idle and throttle position sensor, would be a good idea.

http://members.shaw.ca/agent86/TB-TPS%2bMin-Idle.pdf



Good Luck

dlb435

Your cable and throttle body are probably fine. Sounds more like the IAC (idle air control valve). The OBD1 computer will try to control your idle speed based on several inputs. Engine temp, throttle position, oxigen output, etc. Normal idle cold (under 100 degrees) in park will be about 1100 rpms. This will drop to about 800 rpms as the engine warms up. In gear, at idle you should see 540~600 rpm. I had to replace the IAC, TPI (throttle position indicator) and the MAF (mass air flow meter) to get my idle correct.
Are you getting a check engine light? If so, pull the codes and see whats up.
I also found that replacing the thermostat with a 180 degree setting helped with knock problems. The factory thermostat was a 195 degree setting. What is your engine temp at cruise speed? At a stable 60 mph you will be able to see what thermostat you have. In stop and go traffic the engine will heat up to as much as 230 degrees. this is normal.
It took me several months to get all of my engine control problems fixed. Keep at it and be patient. Your service manual will be a great help. BTW, I thought my car ran well even when it was sick; now the perfomance is just amazing.

Calderone

Sounds like IAC
but i had this problem not long ago
anyway it was something i didn't think
http://forums.corvetteforum.com/c4-t...rmance/2150587

JPSilvaggio

thanks for the new responses. To keep everyone up to date i have ordered the manual and currently waiting for it to come in. I have NO IDEA what an idle air control valve is or what it looks like so i am definitely going to need the book for reference.

Where can i get this part/parts and how much will this project be?

AGENT 86

Read the sections of my manual that I linked you to.

Most parts places will carry what you need, but don't buy anything until you have ruled out the sticky linkage/cable/throttle shaft.

Blipping the throttle to get the RPM's down, does not sound like an IAC problem.

RCapece

I belong to the corvette club of RhodeIsland you can join for $39.00 a year,and you can meet many people that can help you with your issues.I have a 90 vette and made many contacts there.

Droshki

"Blipping the throttle to get the RPMs down" is most definately the return spring on the drivers side of the throttle body being weak. I elected to just add an external spring rather then find out what GM wants for the factory one. You can check this by closing the throttle body butterfly by hand when this is happening. It wont take much. When you blip the throottle, all its doing is winding up that little return spring and so returning the butterfly a tad harder.

Initally I was going to agree that he has an IAC problem too, but Im on the fence until the throttle return spring is replaced/aided.

Granted, as I am sure someone has stated above, crud in the throttle body wont be helping either. But I know about the spring

rfn026

I really hate long distance diagnosing but ......

I would get some throttle body cleaner (not carb cleaner) and remove the throttle body from the car. Then clean everything. This includes removing the IAC. The IAC on my car actually had wear grooves in it when I cleaned it. I replaced it rather than take a chance.

You have to remove the throttle body from the plenum to clean the rear of the throttle body because it seems that most of the crud builds up on the back side. This crud also builds up on the shaft and won't allow the return spring to do it's job properly.

In a perfect world none of this would be necessary. You '85 has not lived in a perfect world. Goggle has posted a lot of my book. You might take a look to see if any of this helps.


Richard Newton
101 Projects for Your Corvette 1984-1996