My car has recently been having an idle problem. Right when I start the car up, it has a little bit of a high idle then it goes down to normal. Then throughout when im driving, when I push the clutch in to come to a stop, it will come to a high idle. Then a few seconds later, it will idle back down. I don't know if it is a possibility or not, but it started happening around when I installed a hypertech cap coil and rotor. Maybe it's just a coincidence. Any ideas on what this could be.

 

Check your TPS and IAC as a start.
TPS : 0.54 - 0.57V idle (no throttle)

and make sure your minimum air is set correctly.

Then check for small vacuumleaks and these simple things.

 

The TPS on those early TPI engines is an area of concern if it's old/original. If it's reading high at idle, it will kick your idle speed up. It's also adjustable to a greater degree than later units- and that means greater possibility of mis-adjustment.

See above post for proper voltage ranges.

 

check the simple things first . my bet is that you have a vacuum leak . the vacuum hoses/tubes are just rubber/plastic . i replaced about 12ft. of hose on my previous 89r/s . OMG ran so much better . vacuum lines may look good but still leak . change all , cheap , & simple fix . good luck .

 

Sorry for stealing the thread, but did you change the hard plastic ones to ?
Did you change to soft rubber ones instead ? or did you go with plastic again ?

Could be good to know for others who thinking of changing

 

any plastic fittings that were broken were replaced . good luck .

 

I was thinking did you replace it with new platic or new rubber hoses ?
and what type of rubberhose if you used that, cause the hard plastic ones are hard to buy..

 

I just checked the TPS voltage and it is within specs, and went over all the vacuum lines and they looked fine.

 

Then have a look at fuel pressure, Spark plugs, Wires, distributor, cap/rotor.

also have a look at your timing.

 

Mine is doing the same thing, it will go to 2000 rpm at start...then after 7-8 sec down to 800 rpm... when I have to stop and apply the clutch its back up to 2000 rpm then down to 800 again. When I disconnect the IAC at idle it stays at 800 rpm but I know this is not the right thing to do. I am going to remove and clean the throttle body and IAC housing and see if this helps. My TPS voltage is correct, timing and vac lines are ok. Maybe my throttle body is just worn out.

 

Well if it working with the IAC disconnected it might be an bad minimum air or bad IAC.
Clean out the IAC passages and make sure its nice and clean inside the throttlebody.
Then re-adjust the minimum air to correct values (guides can be found at iroczone and here at main page)

Get back with info how it turns out.

If its an bad IAC tpiparts sells the AC Delco ones, at a good price
I changed mine out some time ago and it did a big difference, I also cleaned the whole TB so it was like new

 

I replaced my IAC with one of those $50 AC delco's...There is a noticable difference in the quality compared to the cheap ones. I'll get back with results. (If you use small bursts of Either around the engine while running...if the engine revs up there may be a vac leak or a gasket not sealed properly)

 

What were your results after changing the valve?

 

They were the same, I did find that a couple of wires to the IAC valve were spliced and connected with quick connects. I removed them and soldered and heat shrink the wires. Now I have a start-up RPM around 1500 and a hot idle around 800. The engine is 87 version HO 350 crate and I have the original 85 TPI intake. The engine still lopes a bit and I think I have a vac leak around the center bolts of the intake manifold. The angle was changed on the center valve cover bolt engines. I'm still trying to get it to smooth out. It runs like a raped ape WOT. My RPM shift points are set to 7300.....Does idle really matter?...LOL. I recently had a code 43 so I may have to change out the ESC.