I'm planning to do a major tune up and would like some advice regarding servcing the throttle body. I will be removing the throttle body to give it a thorough cleaning as well as replacing the IAC and TPS. When replacing the IAC and TPS, which setting is adjusted first? I know the procedures for adjusting both settings but I'm not sure which is best to set first. I was leaning towards setting the IAC first in order to establish a good base idle. Thanks for any help.

 

Are you having codes with the IAC and TPS? If not than chances are the parts are good and require no replacement. Both parts are expensive and a waste of your hard earned cash if there is no problem with them. To your question you adjust the IAC first than adjust the TPS. About a 5 minute job with your new favorite tool.......the paper clip. Use the paper clips between the wiring harness for the TPS and adjust that with a voltmeter on the top 2 wires.

 

Here is what I would do. The IAC doesn't throw a code, but the TPS will. I would remove the TB and clean it good. Remove the IAC valve out of the TB and clean it good as well. Myself, I would spend the $30 on a new IAC and gasket, but everyone says not to throw money at the problem so you do what you want.

When installing the IAC back in the TB make sure the pintle tip is no more than 1 1/8" away from the flange of the IAC or damage may occur.

To set the minimal idle and TPS: Use a paperclip and ground terminal A and B of the ALDL. With key on, wait one minute then disconnect the IAC connector (this way it blocks the air passage and lets the idler screw control idle). Take the paperclip out and crank the engine, may need to give it some gas at first. Let it warm up, block the wheels and put it in D if auto or N if standard. Use the RPM guage as a guide to set it around 400-600 RPM.

The idler screw is located on the drivers side of the TB, just above the throttle cables. You will need a torx bit to adjust. Once you get it down to where you want it you will need to adjust the TPS. Use two paperclip pieces inbetween the TPS and its harness (black and blue wire) to check the volts with a voltmeter. From adjusting the minimal idle the TPS will probably be off so you will need a different size torx bit to loosen the top and bottom screw. Move the TPS up or down to get it to .54v and tighten it up. Put it in park and turn the engine off. Connect the IAC sensor back up and thats it. I have also hear of people disconnecting the EST to set the minimal idle.

 

Thanks for the help and suggestions guys. I already have both a new IAC and TPS so I will be replacing the old ones. I figure with 107,000 miles and 20 years old, it can't hurt to replace them. Enjoy the rest of the weekend

 

I would also like to thank you guys for the posts - I removed and cleaned my TB - much to my dismay - my RPM's at idle jumped up to 1500. I think you just helped me find my problem - thanks again

 

I am uncomfortable with the part about blocking the wheels,
putting the car in Drive and then climbing under the hood to
work the throttle.

My vote is to have a helper in the driver's seat with a foot
on the brake anytime the car is not in park. Someone who
won't be startled if the throttle is blipped and the car lurches.

.

 

Well on my 86 when I set minimal idle and TPS I usually just put the emergency brake on and put it in drive. I don't block the wheels and I don't pull on the throttle. I haven't had the car go anywhere yet. Blocking the wheel is just a safety feature. I guess everyone does it differently but I don't have an assistant to help. IMO

 

Make sure you plugged everything back in, leaving either one disconnected could cause high idle.