High Idle

[daewoolvr]

Hello I am new here, I have a 99 Lanos 1.6L LX. I am currently in winter and I know that can lead to a high Idle but this is high even after I warm up the engine (even though the engine idles fine when I do warm it up). It gets higher as I drive and it's almost uncontrollable after about twenty minutes of city driving and sometimes it shifts into first rough. I replaced the valve cover gasket, intake gasket, cleaned the throttle body, intake plenum, and replaced the TPS. I have tried the Computer Idle relearn but it did not really work. Whenever I plug in the diagnostic reader I get error code PO442 Evaporative System Leak Detected (small leak). I have run out of ideas on what it could be any suggestions are welcome and thank you in advance.

[Puddle31]

there are a couple of experienced mechanics on here that will have an idea. You can also search the forum for familiar words. I think i recall other people having this issue. Have you checked all your vacuum lines? Perhaps one of them is leaking and changing the idle. sorry I can't help more but give it a few days and one of the regulars will see this and chime in.

[Puddle31]

just doing a quick serach I found there were a few discussions on this issue. One person had similar symptoms. One person on that thread said they had an issue with the Throttle Positioning Sensor. someone else said that the sensor itself may not be bad, however one of the wires could be bad. If you know how to check continuity on those wires you may be able to check that. that might explain why it is doing it when it is cold, and not after it is warmed up and seems to be idling fine. here is the thread topic, but there are also others. Please let us know how it turns out. http://www.daewootechforum.com/forum/vi ... =high+idle

check for vacuum leaks
check TPS
check wires for TPS

[Daniel]

Hi,
Remove the hose coming from the EVAP valve (which is at rear of block) at throttle body and plug the hole on throttle body. If idle speed returns to normal you have a leaky/open EVAP valve.



Look also at rear of intake plenum for integrity of corrugated/angled metal tube from EGR valve.