I installed a port and polished 87mm throttle body on my 07' Avalanche 5.3L today. I noticed when comparing it to my old TB that there was a big chunk of material removed from the lower part of the interior "it looks like a lip in the stock one". Anyways, after installing the new TB and starting the truck, the idle was a bit off but nothing too bad. I gave it a little gas to rev it up just a little so see how the response was and the engine just "runs away". The engine speed will not slow down after i let off gas and return to idle speed but instead slowly keeps increasing rpms. I have no choice but to kill it. This has happened several times now and obviously i'm not even about to drive it with this issue. Any ideas?? Is this maybe just a defective TB? I did not get an engine code error surprisingly.

 

It sounds like its just doing a relearn. Anytime it gets reflashed or the battery is removed for more than a minute it has to relearn how to idle. Unless you are saying it gets to like 4500rpm b4 u kill it.

 

Have a picture of the inside of that throttle body?

 

Here are the pics. Compared to my stock TB, there is a lot of stock removed from the lower part if looking at pic" part of the intake channel. The "lip" is removed entirely. Should I have removed the - post on battery before install? After I pressed the gas a little the rpms would not steady or return to normal but would just continue to slowly rise. I was killing it by the time it was hitting 3500ish rpm. I was releasing gas when it hit about 2500 rpm.

 

Would it be safe to leave the air intake off of the throttle body and do a couple of open air revs, so I can see if the blade is returning to home position when i release gas pedal?

 

It needs the maf sensor to idle correctly otherwise ot may not run or run very rough. Is this a common problem with these ported throttle bodies? Was thinkin about getting mine done but well..........

 

I installed one on my 09 Vette and had zero problems, weather has been too bad to get a chance to drive and really see what difference it will make. The Vette did not not have the big "lip" though on the lower area of it's stock Throttle Body. This concerns me because this "lip" was impressive on the trucks TB. To remove that much stock would seem to make a big difference of some sort..

 

At idle the blade is going to be almost fully closed, not at the spring-determined position (which about 20% TP) as shown in your photo. Try moving the blade back and forth by hand to ensure that it is not rubbing against the throttle bore in any position and that it can be fully closed. It should be pretty much sealed all the way around when fully closed. I would say to be safe no material should have been removed from the bore in the area from the spring position to fully closed.

 

This is a general rule of thumb when porting a throttle body. Stay away from where the blade closes. Before you rev it does it idle ok, or is it only after you rev it that it keeps climbing? I didn't think about this being a DBW setup, the motor may be bad in the throttle body and not closing the butterfly when you let off of the throttle. Because that is what it sounds like is happening.

 

yeap....