TB install - Idle still too high

[Jimmy Lavoie]

I installed a new Throttle Body on my 07 V8 last Sunday. At first, the idle was very high and took a few seconds to come back down. After a short test drive, it seemed to get a little better.



Well, it's been 4 days and it hasn't changed at all. Still doing the same thing.



I guess my questions are:



1. How long should it take the computer to learn? (yes, I did follow the instructions to include disconnecting the negative side of the battery)



2. What should the idle be?



The good news is that it seems to have helped my gas mileage a little - was getting 15.8 all around average, seems to be getting 16.3 now. Again, only 4 days since the change and I feel pretty good that it's a little higher - especially that I've been a little heavier on the pedal than before (having a little fun).



Anyway, any thoughts on the two questions above?

 

[Todd Z]

Jimmy, what is your idle now ???



My truck was 650 from the factory, It is now 850-900... Runs, takes off, idles smoother....



Also if your going by the factory tach, it can be slightly off too....



Todd Z

 

[Jimmy Lavoie]

Yes, I am going by the factory tach. I'll pay closer attention to the numbers based on the tach and post later.



Sounds like the idle should be a little higher then original factory TB settings.



I guess the thing that concerns me is the fact that when I'm driving, and release the pedal, it hangs at a higher RPM for a few seconds before coming back down.



I can certainly live with the higher idle.



I'll let you know.

 

[user 64972]

Wasn't the high rpm issue part of an early TSB? Has the ST been updated with a newer TSB? May have been an underlying issue that was magnified by the Todd Z modded TB? Just a thought?



Gary G

 

[scott degroot]

Seems to me that no matter what size the throttle body is on the vehicle that it should still idle at factory spec, afterall when the tps is at base setting and the vehicle is not in motion the pcm should command the iac to lower the idle to a preprogrammed setting...bottom line. Is the tps adjusted accordingly(is it adjustable with the aftermarket throttle bodies). I have heard talk on this forum about turning the screw that adjusts the throttle plate to allevieate throttle plate sticking. Problem with this is that if the tps isn't adjusted the pcm thinks that the vehicle is under part throttle because is never sees the base voltage on the tps and therefore never returns to idle...I am just babbling here..personally I think that the need for a larger throttle body is a bunch of hooey on a stock vehicle and can and will only lead to problems...such as high idling. Have you checked for a vacum leak??

 

[Todd Z]

l1,



On his 07 V8, there is NO IAC motor, the idle is all computerized.....



There is a 10% range that the new 4.6 is programed at the factory to run in, It can be at the top of the range or the bottom..



His TB is also drive by wire too, IF he turns the adjustment screw he will snap it off and void the warranty..



Secondly the TB he bought from em is a Brand new OEM ford unit that I modify, IT is not an aftermarket...



I simply think his engine is seeing the extra air flow at idle and is raising the rpms...



As far as the hanging at the higher RPMS I don't know what is going on there...

Could be a leak, or a bad TB.....



Todd Z

 

[Jimmy Lavoie]

The Idle is at about 6 - 650 based on the tach inside the truck. That seems fine.



I will check all connections and bolts to make sure there is no leak. Like I said, it's the hanging that is weird.



It does run fine though - no other complaints (except the tranny shifting - which is a completely different issue)

 

[scott degroot]

Sorry Todd I forgot we were talking about an ETC system here. I have to ask the question though, when you modify the t/b do you completely bore through it and have a new throttle plate made or what. I am just trying to figure out exactly what is done to these so I can better understand the affect they have on the engine/pcm. My main concern with modifying one of these would be a safety issue witht he traction control, abs systems and stability system. I could also see trans shifting issues with this also due to the pcm controlling the etc system during trans shifting.



JJ, your idle of 6-650 is very acceptable just make sure that you have no vacum leaks.

 

[Collin Lyon]

I just pulled into work, and my idle is appx 700-750 rpm (stock), if this is of any help . . .

 

[Aaron Yarbough]

JJ, i just read you rpost about the tranny shifting.....have you had your PCM updated by Ford since you purchased your truck? See the most recent TSBs in my library, I would have the latest TSB applied to update your PCM.