TOPIC: 2000 Chevy 4.3 L Vortec silverado 1500 4 spd.Auto Trans

Mod on 2000 chevy 4.3L silverado 1500 auto trans. 4 spd.

Building up thin wall before grooving


IAC scooped out T.B. wall before mod.


Smoothing the scooped out wall, notice plastic piece under the jb to keep it out of the hole, after the jb sets for a little while you can sculpt it by hand , sort of like clay. You need to pull this plastic out before it is permant set up. let it get fairly hard but still feel some give to it







Smoothed wall after removing plastic




I was able to put jb into the iac valve hole with a wooden ice cream stick , with the tb laying on flat surface with a playing card under it , it would be best to use a flat thin plastic instead , like from the side of a milk jug, you need to have a long narrow knife ready and after puting the jb in the hole get it out from any unwanted areas notice the area the valve needs to go into and do not block these areas.


IAC mod with 1/8 inch hole




The Groove from filter side , used big bit



Groove from engine side




I also did the pcv and seald off the pcv vacum ,jb in the pcv, did not change the oxygen sensors yet, but did the computer relearn. Also gave gas tank some meds. for Headache......Greg P

This is a photo of the throttle plate before shapeing , notice the edge is black , i took a black permanant marker and went all around the edge before shaping, you want to leave a small portion of this black when shapeing the plate so as it will still seal.



This is a photo of the flat side of plate after shapeing, in this photo the plate has not been smoothed , after shapeing i used a chain saw file and pulled it side ways across the plate and smoothed the milled surface. I used Dremel 9933 tengsten carbide cutter to do the shapeing. I held the side of the plate toward me as i shaped the plate so as to see how much was coming off. Only had the dremel at about half speed , it took about 45 min. THE SIDE FACEING OUTWARD FROM THE MOTOR IS THE SIDE YOU SHAPE




Two more photos of the shaped plate SORRY THEY ARE BLURRED








This is a Photo of a drawing that I made they explain themselves, I will make a comment on the IAC inflow sculpting, Have you ever taken a deep measuring spoon and placed it under the water faucet in your sink, the water will go into the spoon and shoot strait back up into the air, it goes in and back out in the same direction it came , that is what i think is going on in the IAC air inlet on the side of the throttle body wall.



After doing the groove and iac and tb wall sculpting and pvc mod. I had to adjust the idle screw on the side of the TB to get the motor to idle, i had it set at 600-650 rpm. After sculpting the plate the motor started and ran at 1500 rpm so i had to idle the motor back down to about 700rpm when you pull it into gear it is about 600-650 rpm...........Greg P

Information on how the IAC responds Jan 6 2014 , it is -2 deg below zero here today , no better time to see if modifications are ok,...... I turned the ignition key to run position and let the fuel pump do its thing, turned off and back on again to be sure pressure was built up in fuel system, turned ignition key to start and motor started at 400 rpm and slowly climbed to about 650 after about 45 seconds , i have not touched the accelerator up to this point. Then I move the truck and use the accelerator pedal, after moving the truck and stopping the truck is ideling at 800 rpm
in park when truck is pulled into gear it is at about 700 rpm, with the truck in park and heater going and lights on it is about 700 rpm......went out for a short drive and have no problems.............I think there will be no stalling problems with this IAC modification.

...........Greg P

Another nice writeup w/ excellent pics, Greg! I'm curious to hear about how your IAC mod performs. Meaning does the RPM go up sufficiently at cold start? That would be easy to tell during the first part of computer re-learn in driveway. If it goes up to 1000-1500 RPM or similar when cold, or at least say 300 RPM over hot idle speed, then I would think the IAC can still do its job. And remember if A/C equipped, IAC will raise RPM to support additional load on engine at idle---don't want any engine stalls at a red light for example!

'Nother little point to remember about idle RPM's VS> engine loads, is many vehicles increase idle RPM's if the power steering is engaged at idle RPM. IAC is the idle RPM controller. If you notice a wire coming from somewhere in power steering system, and don't know why it's there, it's an input sensor wire to ECM to signal for more RPM to support added loads from power steering pump.

Your pics show good strategy RE: JB weld placement to do 2 things: first back-fill of thin area in IAC port, behind where Groove is going to break thru; secondly, expert use of JB Weld to do IAC port fill-in, and explaining important technical points of it's use. Took me a moment to understand why you fill in the IAC approach notch but I get it now- you're smoothing out the boundary layer of airflow approaching the critical center of the Groove- Im guessing that this will enhance the Groove effect maybe at least as much as IAC restriction, maybe more,,,?

Other Gadgetfolks need to look at yer pics CLOSELY, they tell the story well!

Very nice work, IMHO. You get it about full scope of doing the Groove, Greg.

You might want to re-post this thread, add it as a Service Bulletin in the Index area, list as an IAC Mod. Maybe title it as "IAC Port Mod-Airflow Sculpting". It's that good, IMHO.

Do let us know about results of this one, and what Idle RPM results are like under different operating conditions.



Been following along w/ the Headache Remedy, trying to find un-coated aspirin.

thanks Mucho Greg!

Tracy G

namtegdag Ky. Thanks nice write up and pictures
geraldc

Hi Tracy G

Thanks for your input, i apreciate your opinion, ....I had to adjust the idle screw on the side of the tb to get it to idle, my other 4.3 was the same way until i did a throttle plate sculpting on it , then i had to idle it back down with the screw on side of tb. I have,nt had time to sculpt this plate yet. On the first 4.3 it was slow to idle even before i did mod on the intake wall of tb. So that is not what made it idle slow. When i get time and weather is fit i will sculpt the plate on this one too.

Question : is it o.k. to adjust the idle screw , or does it effect the throttle position sensor, my question is does it matter that i adjusted the idle screw??

As for the uncoated aspirin , the coated ones says coated aspirin on bottle and have slick look to the surface. the uncoated will have a more grainy look to the surface and does not say coated on bottle. if they are in clear bottle you can see them . Cheap dollar store stuff. Haven,t heard back from Dan on the hydrogen peroxide, what is your opinion ,is it a drop for each ounce of carrier??

Tracy , I was thinking about your adiction when i was loading all these photos, hope you found your happy place with it

Are you sure i should place this in Service Bulletin I figured that should be for seasoned groover. If you have the ability you can place it wherever you like......Greg P

Thanks geraldc,

Please let us know the results you get , when you make your trip, useing the aspirin, You may be the first to make a report on it, hope all is good...........Greg P

Thanks for th-th--the f.f.ffixx, the pic fix, G-Greg! I'm b-better now!

Idle speed screw, I'd say no worries there, long as it's not adjusted way far.I've adjusted a couple in combination w/ IAC Mod's before, doesn't usually need to adjust all that much. And thanks for additional info about idle speed/throttle plate shaping--that's good useful data as well!

For the Headache Remedy, well I read/interpreted it as 1 drop of Hydrogen peroxide per total dose, as in 1 drop to 1 Oz of grain alcohol (Everclear is what I'll try) with 6 325 mg. plain uncoated aspirin--all this to 12 gallons of gas. Gonna find uncoated aspirin first, Everclear is easy to find.

And Thank you also, Greg, for starting the Acetone thread that lead to the Headache Remedy, thanks to Dan M as well of course!

Greg you're a Pathfinder for us all, my hat's off to ya!

I think when you get the throttle plate shaping done for this one--and confirm results about how ide RPM is effected thru this whole method--that all you did w/ this one deserves a service bulletin of it's own. There are several important clues about this whole IAC mod that you have explained and illustrated, and I think it would serve as reference Material for all present and future Gadgetfolks. Perhaps you would consider doing that when you're ready. It would be a "cleaner" read if the IAC itself, how ya went about it, how idle speed screw was adjusted, throttle plate shaping--the whole thing but complete/concise, posted as a Service bulletin separately. Good to have it listed/titled that way. I have gone into Serv. bulletins even to find my own posts before, handy to have important stuff there, not just buried in a thread!

thanks, to all who add to the combined Knowledge, that's how we Grow.

Tracy G

Hey, Tracy G

Look back I added more info, Plate shaping etc.....................Greg P

Question : Can I click a topic icon and move my first post in this thread to Service Bulletin??
if so it would save a lot of work.....which would be topic icon for Service Bulletin???? Thanks.................................Greg P

Hi again, Greg P.

I moved this excellent thread to Service Bulletins, and added IAC/ Throttle Plate Shaping to end of Subject title, using Admin. tools access I have, granted to me by Ron many months ago. I do hope this is OK w/ you, kind sir.

You've done such Great work showing all how you have done this- I just wanted it to be available in the Service bulletins area for future availability. Though it's not written explicitly as a Serv. bulletin, the meat and content ARE there, IMHO!

Seems obvious to me that the Shaping really increased airflow past the edges of the plate. So much so, you had to back idle speed screw off . question: in this config., how much RPM influence does the IAC have? At cold start, do you get a high idle RPM that then reduces as engine warms up? Does truck have A/C, if so does Idle RPM go up when A/C engaged?

Points to consider--We Gadgetfolks, being workmanlike and understanding our vehicles, may be OK w/ having a more fixed Idle RPM--but others we do the Groove for could experience a problem or be confused if the vehicle behaves different after Grooving AND including IAC mod and throttle plate Shaping. I'm just thinking the factory put that IAC there for good reasons. Cold weather we usually want initial RPM to be a little higher to help during warmup. With A/C on, extra load can bring idle speed too low, esp. if other loads (pwr. steer, alternator load from headlights, heater, stereo, etc.) are present. All the more so if engine is 4 cyl, or lower output. IAC is Idle RPM controller.

Factory (I'm thinking again here) put these relatively HUGE IAC ports/valves there, so the IAC could still function even if the darn thing was super grungy. Grung-ed up IAC w/ a very dirty pintle head-(pintle can get stuck open) can cause unexpected runaway idle speed, where vehicle lurches out ahead, just like a stuck open throttle! So cleaning the IAC pintle/port ought to be part of Grooving even If not Mod'ding IAC, IMHO.

And here's a bit to think/research about, for those interested: Coanda Effect. This will reveal a TON of info about airflow, and how it can "stick" to a curved surface...

Excellent thread, writeup and pics, Greg

Tracy G

Hi Tracy ......Look back to bottom of first poast, i made a report on the response of the IAC mod, it is 2 below zero here today.

As for the Coanda Effect......that is why i sculpted the throttle body wall , let that air slide into the groove and hopefuly do a better job..................Greg P

OK, Greg based on you cold weather start today 1-6-2014, sounds like you have it dialed pretty well! Time will tell the full story. Good for you buddy, I'm really lookin' forward to your future posts!
Yes, the Coanda Effect is full of thought creating ideas. Glad you knew of it, a google search of it reveals a LOT. Another Gadgetman named MPG Mike brought it to attention quite awhile ago. That guy is a walking gold Mine of useful info, I hope he lurks here on this forum, wish he'd post something now & then...

Congrats Greg on Excellent work, Results, and Posting of same! Thank you!

Tracy G