High idle with BBK

[Limited Ex]

Ok guys, I did a search, but could not find a solid answer. I have a BBK throttle body, I have had it for awhile, and over the past few days I changed a bunch of gaskets in my engine, and both O2 sensors. I started my Ex up yesterday, and noticed that it idles right at 1000 rpms. When I drive it, it runs great, when I come to a stop, it idles around 500. But once I put it in park, the rpms shoot up to 1000, and this was without the AC turned on. It idles kind of rough too, but I cannot imagine what it would be. I did adjust the idle screw on the TB a little bit a few months ago, and that helped, but after I did all this work it has picked up some. I changed the IAC and put a new sensor in, so I know its not that. Should I adjust the idle screw some more? Oh and I also cleaned the MAS sensor, so thats not the problem either. Just to be certain I did things right, what is the proper way to adjust the idle screw on the BBK?

 

[DonM]

Sounds normal to me.

My 95 runs around 600-700 rpms in drive at a stop! In park(warm) it idles around 900-1000 rpms.

Did you disconect the IAC when when adjusting the TB screw? It should run around 500rpms when the IAC is disconected.

My engine also runs rough, but not nearly as much as it used to.(Apten Chip) But i guess it's just normal for are engines?

 

[Rhett]

When you switch into Park it should not raise the idle much at all. This IS the factory spec. I had to do a lot of adjusting with the IAC and throttle screw to achieve the factory idle spec with my BBK. Finally I got it.

 

[DonM]

Rhett Browning

Where is your rpms? Both in drive and park?

 

[Limited Ex]

I have read that I am supposed to disconnect the IAC when adjusting the throttle screw, but whenever I unplug it, the engine cuts off and will not turn over until I plug it back in. Unless you mean disconnect as in physically remove the IAC from the manifold?
Rhett, I noticed that you said you had to do a lot of adjusting with the IAC and the throttle screw, how did you adjust the IAC?

 

[Rhett]

LimitedEx. No need to physically remove the IAC; here's the way to adjust the IAC.

At first I couldn't figure out what was wrong:

http://www.explorerforum.com/forums/showthread.php?threadid=64599&highlight=BBK+Throttle

So I returned the TB, got a new one. This time they sent me all the install instructions.

1) First disconnect neg batt cable.

2) install the TB.

3) Then disconnect the IAC. (unplug it's electrical connector).

4)**If the truck won't start with the IAC disconnected, you need to open up the throttle plate on the TB a little until the truck will turn over.**

5) Turn the adjustment screw on the TB a little until the truck will start with the IAC unplugged. Then make sure the truck idles at approx 500 rpm with the IAC unplugged. If it idles too low, like 400 rpm, go and turn the TB screw to open the plate a little more. If it's too high, close the plate. You can adjust the screw while the engine is running. Do this until you get 500 rpm.

6) Then, shut her down, reconnect IAC, and restart the truck. The idle should be about 600-650 rpm. If it's not, shut down and adjust the TB plate again.

 

[Rhett]

DonM: 600 rpm in both idle and park.

When my TB plate/IAC were mis-calibrated, the truck would idle at 750 rpm and when I shifted into Park it would jump up to as high as 1100 rpm. I couldn't live with that.

 

[Limited Ex]

Thanks Rhett, I will do that the first chance that I get! I paid more attention to my trucks idling this evening, and when I am in Park, its up around 1100 rpms, and 6 or 700 when stopped.