[dsmlinc]

My truck idles to high to pass emisions, it idles at 1320 and needs to be below 1100RPM. I can change the timing to slow it down but i dont think thats the best way, any ideas? ... I have looked for a vacuum leak and haven't found anything that helped.

 

[wilson07]

If its tbi theres a screw you can tighten or loosen to change the idle

 

[dick verde]

i would check the timming if i t is ok then i wouldnt mess with it because the has to be a other reason , vacumm leak, brake booster leaking vaccum, screwed up sensor,

 

[dsmlinc]

its a 89 2.8... where is the screw because i looked and i couldn't find it

 

[84S-10]

mine is on the left side of the carb if ur standing right in front of the truck

 

[rallyhard]

Check out this thread- http://www.s10forum.com/forum/showthread.php?t=237451.
Might help.

 

[pare_john]

how did you go about looking for vacuum leaks? the the unexperienced they can be tricky to find

 

[84S-10]

i spray carb cleaner on all the vacum lines and when it sputters uve found the leak

 

[betterthanyou]

If its tbi theres a screw you can tighten or loosen to change the idle

No you cant do that it is capped from factory and it is not going to change anything.

I am willing to bet the IAC is stuck open or not working at all. Remove it and check. Also check to make sure the seat where the IAC pintle seals against is clean.

Set timing at 10* BTDC with the timing wire disconnected and leave it. If you are trying to pass emissions this is where it needs to be.

 

[pare_john]

while ther IAC is out verify the pintle length

 

[wilson07]

No you cant do that it is capped from factory and it is not going to change anything.

I am willing to bet the IAC is stuck open or not working at all. Remove it and check. Also check to make sure the seat where the IAC pintle seals against is clean.

Set timing at 10* BTDC with the timing wire disconnected and leave it. If you are trying to pass emissions this is where it needs to be.

Actually its just a tin coating thats easy to scrape off it adjusts the throttle cable tension so it makes it possible to raise or lower the idle.

 

[betterthanyou]

Tin coating? What kind of narcotics do you smoke?

It is a steel cap pressed into the aluminum housing. The idle adjustment screw WILL NOT lower the idle speed. The IAC is what controls the idle speed and for some reason it is open too much. It is either broken, stuck open or for one reason or another the ECM is commanding it open too far.

The minimum idle screw will only set the lowest idle point of the engine. It is set from factory at something like 500RPM and is capped. It never needs to be changed.

Here are pics and instructions I wrote on removing and adjusting the set screw. dsmlinc you need to take note that this is not the cause of your problem.
http://members.shaw.ca/betterthanyoutoo/how-to/TBI Idle/tbiidle.htm

 

[wilson07]

On a 2.8 that might be so but on my 91 2.5 that screw has a coating that scraped of with a pocket knife. It was a t 15 maybe larger screw that altered the idle on my truck. Not all throttle bodys still have that coating still on the screw (expesialy if its used) so backing this screw out some would lower the idle on his dime.

 

[1988S10]

ummm i'd spray carb clean around the throttle body gasket. this is a comon porblem i've seen at work. make sure the throttle plates close all the way. cause if the they are sticking it could cause a high idle. and your taking this thing to the test hot right. cause the TBI motor idle high till warmed up.