High idle speed on cold start in a 93 chev lumina z34

SOURCE: engine stalls after cold start-up & release from high speed idle

I had a similar problem.  I found the filter cartridge below the pcv valve had carboned up, and after the crank case pressurized, oil was forced out the pcv supply line to the throttle body.  The idle air control valve solenoid got oil in it and caused my problem, but only when it was cold.  The pcv cartridge is accessed by removing the pcv valve and the rubber fitting that the pcv valve mounts in.  It can then be fished out with a pick set, and it is a pain because you can't see it, but you can get you hand back there.  I hope this helps you.

SOURCE: High idle speed when the engine is cold

The high idle speed at start up is normal. As the engine temperature increases, the engine idle should kick down automatically. Insofar as the emissions results, if there were a problem, the check engine light should be on. If it is, take the car to an autoparts store and have the fault codes read. Most parts stores will perform the scan for free. If the check engine light is not on, and the idle question was all you were worried about, you are good to go! Hope this helped and best wishes.

SOURCE: idles high to low repeating at cold start

Check the vacuum hoses for damages or loose connections.

SOURCE: 87 chev van 350ci,failed 1 of 4 emissions test(HC

Hydro Carbons are usally from an engine missfire. It may be that it is such a sligh miss that you cannot feel it. What is your timing set at? I would try setting it at 2* advanced and see what that does for you.

SOURCE: 91 mazda 626 erractic idle surge when engine is cold

My '91 626 did the same thing. I tested the throttle position sensor, and it was good so that wasn't it. The other likely culprit is the Idle Speed Control valve, or Idle Air Control valve, which is a $500 part new (more than I paid for the whole car). I pulled one off a 626 at the salvage yard and got it for 3 bucks, put it on (it's an easy DIY, just 4 philips screws holding it to the intake manifold), however I can't be sure that solved the problem, since I haven't run the car much since then. It would seem the most likely cause, tho, and a cheap fix if you go used. Other possibilities: O2 sensor or Mass Air Flow sensor?