Can anybody tell me what the normal idle speed should be? im at about 1100 rpm on my 99 5.9 while in park.
And where and how do you adjust the idle speed? or can you adjust it.

 

should be about 1000 when cold, about 600 when warm.

idle speed is controlled by IAC (idle air control) on the rear of the throttle body. it should open/close to change the amount of air that bypasses the closed throttle plate. they can go bad. you can see it operate with air filter removed and looking down into the rear of the TB. you can also hear if operating by the change in pitch of the whistling/sucking sound.

another cause of high idle is a vacuum leak that lets in more air than the IAC can compensate for. for a small vac leak, the pcm will command the IAC to close up a little more and it can compensate. but for a major one, the most the IAC can do is close completely up.

 

Spray starting fluid around your manifold and see if the idle rises.

 

I concur with vac leak check.

Confirm that your accelerator cable was not binding up. May need to remove the air intake off the throttle body for good visual checking. Cycle the butterfly maybe too.

How new is this idle condition? Cold morning? Anything maintenance-wise or other you did prior to this?

 

ill try all this stuff, even hot its about 1100 rpm. im thinking im hearing a hissing/sucking sound that I haven't heard before so ill look for a vac leak. thanks all ill keep y`all posted.
tom

 

well I found the vac leak got new hose for that matter of fact I replaced every vac hose on the truck. now the other problem is my tranny. the first night it went below freezing here the tranny acts like its trying to take off in 3rd. when I manually shift it down into 2nd it takes off normally. any ideas out there?

 

If you let it warm up a bit before you drive it, does it behave?

 

no it stays like that even warm im thinking it was just its time to go. just so happened to fall below freezing


I put a code reader on it and it says D1765 that's a 12v relay seems to simple what do yall think
just reran the code reader and comes up with 3 codes P-0735 Trans relay circut p-1765 trans 12volt suppy relay.

so should i replace the relay first and see if that doesnt cure the p-0735 problem if the relay is bad that means no voltage to the relays in the transmission right? And all the transmission relays (inside) are new just replaced last year

the P-0443 evap purge solenoid circut

all this seems to be the same area??

 

That code is whining about the control circuit for the trans relay. Basically, I think it is tripping the relay, but, not seeing anything from the trans to let it know that it is indeed powered. Could try swapping the relay with the horn relay, and see if that changes anything.

 

after putting a new relay in im down to one code now, P-1765 saying its a trans 12volt supply relay isn't that what I just replaced? I`m corn fuzed now.


Any ideas guys