my 1990 z24 is idling to low at 5oorpm after warmd up how can i fix it?

Reply

  #1  
Old 01-21-10, 09:05 AM
9
Member
Thread Starter
Join Date: Jan 2010
Location: sheboygan,wi
Posts: 2
Received 0 Votes on 0 Posts
my 1990 z24 is idling to low at 5oorpm after warmd up how can i fix it?

hi. i does anyone know wat the problem is with my 90 z24. the reason being is that when i start it the car idles at 1000rpm but then when i drive it and stop at a stopsighn it idles rough at 500rpm.does any one know how i could fix it?
 
Sponsored Links
  #2  
Old 01-21-10, 09:48 AM
B
Member
Join Date: Oct 2008
Posts: 1,312
Received 0 Votes on 0 Posts
I don't know about your specific vehicle, but...

In general with a fuel injected engine, the idle is controlled by a valve called the "IAC valve" (Idle Air Control).

And the engine computer mostly controls this.

On some vehicles engine coolant is also used to control the IAC valve. Cold does one thing, hot another.

For the electronic portion, this is based on the position of the throttle. There may be a switch with detects that the throttle is totally closed. This tells the computer the engine is at idle and the computer then takes control of the idle by adjusting the IAC valve.

On others there is just the "throttle position sensor" and this would tell the computer is the throttle is closed.

IF THE THROTTLE can't completely close due to crud or dirt, the computer will not attempt to control idle. Or if there is a switch and that switch is not working.

For the switch, remove the connector, then test with a continuity tester to be sure it is working when the throttle closes. How to use a continuity tester...
Testing fuses Page

Then this all works by allowing more/less air into the throttle body. If the openings are clogged, then air can't get in!

Also the PCV and associated air tubes provide a bit of air for idle. Be sure these are all clean as well.

Replace main air filter too if it needs it.

As to testing the IAC valve, this is typically what is called a "stepper motor" and takes advanced electronic testing equipment to test it.

So if cleaning does not work, take it to a mechanic.

If you want to learn how your specific vehicle works, you can order a factory service manual set from your dealer and this would have a "description of operation" for this (and everything else). Also troubleshooting instructions for your specific year/model vehicle. This would also say what the idle *should* be when warm/cold.
 
  #3  
Old 01-21-10, 01:47 PM
9
Member
Thread Starter
Join Date: Jan 2010
Location: sheboygan,wi
Posts: 2
Received 0 Votes on 0 Posts
thanks bill190, I'll get right on checking those out and get back to u on it.
 
  #4  
Old 01-22-10, 05:09 AM
the_tow_guy's Avatar
Group Moderator
Join Date: Feb 2001
Location: SW Fla USA
Posts: 11,943
Received 48 Votes on 38 Posts
Just to expand a little on Bill's cleaning advice. When you get the air intake hose off and can get to the throttle plate, give it a good going over on both sides with an old toothbrush and some carb cleaner. Also the throat as well. Often this alone will correct the low idle.
 
Reply
Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description: