high idle

i have a 88 cougar with a 302 in it my problem ia s fast idle. i changed the iac but still fast idle. any ideas so i wont keep replacing parts i dont need to? when started cold it revs up then down till it
finds right rpm. but when hot, i keep a fast idle. i want to fix it before i lose a ujoint as it jumps in gear. please help.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

First: Make sure the PCV system is in good shape, including the oil-separator screen below the PCV valve hole. now to troubleshoot: Then get engine warmed up and disconnect/plug all vacuum ports on intake EXCEPT the fuel pressure reg.
Then stop, disconnect IAC harness, start and check that engine idle is about 500-550 rpm. If above that or still fast idle, you either have a vacuum leak or someone has messed with the stop screw.. but if cold idle is good, I doubt either
I suspect, if idle is good (lower than 650) with IAC plug disc; and the Check engine Light comes on with key on, then goes out, and doesnt show with engine running, you may have a bad Throttle Position Sensor (TPS) - or wiring to it. Bad TPS doesnt set the CEL in EECIV (or most of them, anyway).
If it is still the adjustable version you need borrow a DVM and set it to .90 to .99 volts with the throttle on the stop screw.
--
Yeh, I'm a Krusty old Geezer, putting up with my 'smartass' is the price
you pay..DEAL with it!
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Backyard Mechanic wrote:

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
caint find a pvc valve. i got a hose coming from the valve cover straight to trottle body. shogun64 wrote:

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Unless it's a weird setup and the PCV is in Valve cover and that hose goes to intake between TB and valves, it's there... back of engine, into cam valley.
--
Yeh, I'm a Krusty old Geezer, putting up with my 'smartass' is the price
you pay..DEAL with it!
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
shogun64 wrote:

The PCV valve: http://markvii.homestead.com/pcv.html
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
thanks for the picture Sharon K. Cooke wrote:

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 17 Jun 2006 17:47:06 -0700, "shogun64"

BYM's procedure doesn't find it, you may have a leak between the upper and lower intake. Problem was mostly in trucks but , not unheard of in cars.
Lugnut
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
lugnut, i think your on to something. ive been noticing that when i turn on my heater which is vacum controlled they keep opening and closing. could that be related? lugnut wrote:

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 28 Jun 2006 13:38:29 -0700, "shogun64"

Not likely that the intake problem would/could cause that. You either have a bad vacuum check valve or a vacuum leak in the hvac. This is beyond the manifold. If you have a large leak in the hvac control, it could result in high idle.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here. All logos and trade names are the property of their respective owners.