I just rebuilt (new gaskets, IAC and cleaning) my throttle body. Trying to get rid of a very rough idle when cold with no success yet.

My question: On the driver's side of the TB there is a small vacuum line that connects vertically to the bottom of the TB. What is the function of this line? There is no noticable difference if I disconnect it when running. The line runs from the TB to the top of the vacuum bottle.

 

On my 86, that line fed vacuum to the EGR diaphram.

 

Forgot to mention that there's no discernable vacuum present at the end of the line. The line from the bottle goes to a "Y", one side to the bottom of the TB and the other "T"s off somewhere.

 

I believe that line will only see vacuum with TB blades more open than idle.

 

This is how my 86 is too. That vacuum line supplys vacuum to the EGR.

 

On my car that goes to the gas evap. system, the line runs past the alt. over to the front drivers side headlight area. On my car if I unplug that it makes a vacuum leak.

 

This vac diagram should be correct for your year

 

Gracias,

The line in question goes to the EGR valve and solenoid, as well as the TB. I'm no wrench by a long shot, but I'm guessing EGR is not going to figure in this rough cold idle problem. I was curious why I didn't see any vacuum present on the line at idle, but as posted, probably needs rpms to show.

Not sure what to check next. Must have got the TPS close when I put it back together as it ran about the way it did before I rebuilt the TB. I'm wondering if I need to check the TPS switch adjustment or move on to the fuel rails or what. The rear of the TB was filthy and looking back into the hole it made, the same. Any ideas ??

 

If your egr is leaking when its cold fast idle,it can cause stalling,stumbling or rough idle.Here a quick way to test it,go to the parts store and buy some rubber vacuum caps in the HELP section where they sell them parts with the label Help on them.Plug the TB and egr itself with the caps and start the car and see if the idle changes to better.If so,theres a good chance theres a egr problem.

While the egr works at part throttle,if its sticking it can allow the exhaust gasses to pass through early and cause the idle problems or stalling.

Also,not trying to be a azz,it may help to have someone hook up a scanner to see what the TPS is and also while the car is running,what the TPS,02 readings,and IAC counts are.

Sometimes one needs to reset the IAC and ensure the minimum air speed adjustment is done(if the TB screw has been turned or tampered with) but not alot of techs out there these days know how to perform this simple,but super effective way of getting the car to idle right.

I used a snap on scanner before to see what my IAC counts where,and it showed me less than 5 at warm idle,and knew right away it was an incorrectly adjusted minimum air speed adjustment needed it done again.It was reading 0-2 counts,which is false air or a incorrectly adjusted screw,and I remember I had turned it out some to bandaid a problem.

The fix put the IAC counts from 0 to 7 at idle and fixed my idle problems.

Just giving you an example how a scanner reading can help guide someone to the correct diagnosis if theres a problem that doesnt seem to cure no matter what ya do!