95 intake tunning valve
- Thread starter MIJimmy
- Start date
Molson02536
New member
A dirty IAC (idle air control) valve will cause what you are experiencing, try cleaning the IAC first before replacing it. You can clean it with throttle body cleaner through the throttle body, just pay attention to the IAC passage ways to get the IAC cleaned from carbon build up.
Here is a link to where the IAC is located on your throttle body, number 4 is your IAC that needs to be cleaned or replaced. Good luck and keep us all posted.
The other thing too is that it's been know for the throttle blade to get stuck and not fully close, inspect the throttle blade to ensure that there is no binding cause air to pass through the throttle bore. Keep me posted and did you ever get your vent to work 100% again???http://www.compnine.com/index.php?u...delid=6872&capuid=1&majorgroup=03&grouptype=B
Nope on defrost vent havent looked at yet. About high rev i have replaced idle air valve cleaned the passage. if i use carb cleaner on iav map sensor and tunning valve it run great for a couple start stop cycles then does it again. tried doing them 1 at a time to figure out which 1 seemto be tunning valve. some times it will go couple days fine then starts doing it again. thought it might be ground issue so i add a ground strap.
Molson02536
New member
Try disconnecting your MAP sensor and also your IAC when your have your rev down. Disconnect them one at a time to see if it's the MAP sensor that is sending a bad signal to the ECM causing your IAC to open when it should be closed. Here is a link to retrieve your DTC codes if you have any, address them and clear the codes, test drive and recheck for codes. Keep me posted and keep up the great work and recheck your vacuum lines. Bad or cracked vacuum lines can also cause the issues your having with the high idle and bad vent operations.
Information on the Tunning valve and why it's there, In a naturally aspirated engine, the piston drops creating an area of low pressure in the combustion chamber that is less than atmospheric pressure. When the intake valve opens, the air from the outside is sucked down into IM runner. Now, when the valve closes, where does all of that air being sucked toward the valve go? It does not just stop and wait. Rather, it backfires. It strikes the closed valve and travel back toward the plenum (this is called a rarefaction wave, by the way). This is no simple wave, it determines a lot.
Like every wave, this wave has amplitude, frequency and negative pressure. It turns your plenum into a resonance chamber. It bounces around and builds energy (called spring effect, as the pulsation looks like a spring being pushed in). So it now has positive pressure.
Now, the intake valve opens and air is sucked down into the combustion chamber. But it's being assisted by those wave lengths, it's traveling with much more energy behind it. This is what is known as resonance tuning. The trick to resonance (or sound) tuning of the IM is to have these maximally amplified waves arrive at the intake valve just as it opens . What you want is to have it so that when the intake valve opens the CFM into the cylinder higher at a given engine speed or rpm.
Now, to select the proper sized plenum for you naturally aspirated motor. General rule of thumb is that if you make peak torque at 5000 RPM on an efficient motor, you will want your plenum volume to be about 50% of the motor's actual displacement for a six cylinder. If peak torque is at 4000, then do 40%, and if it's at 6000 do 60% etc. I don't know what it is for stock motor! Honestly, I'm too lazy to look it up right now. I'll look it up later and come and change it if I'm wrong. You can find some cool information from this by looking at your dyno, your peak volumetric efficiency will be where you make your peak torque. My Jimmy has been Dyno tuned with internal engine parts replaced so mine will have a different reading then stock.
So what does all of this get you? Torque. It will not help your horsepower as much as most people, honestly. Having the larger volume is what that's all about. All of this wavelength pulsating crap is to give you gobs more torque, and if you're anything serious you know that torque is what it's all about. This is where intake manifold tuning comes into play, just a little FYI.
http://www.troublecodes.net/GM/
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Well it looks like i may have found the problem. It was started fine after 50 start ups so i unpluged things one at a time got to throttle position sencer it reved up pluged back in came down. Some one did a crapy splice job in the wireing. Man i'm glad thats over. Next driveing down the road at a steady speed the rpm jump 200 and come right back down. It surges like this only some times any idea's? Also does the trans have to be opend up for the corvette servo. Molson thanks for your help!
Molson02536
New member
Well it looks like i may have found the problem. It was started fine after 50 start ups so i unpluged things one at a time got to throttle position sencer it reved up pluged back in came down. Some one did a crapy splice job in the wireing. Man i'm glad thats over. Next driveing down the road at a steady speed the rpm jump 200 and come right back down. It surges like this only some times any idea's? Also does the trans have to be opend up for the corvette servo. Molson thanks for your help!
You don't have to drop the transmission pan to swap out the Stock servo with the Corvette servo, and takes under an hour to do. it was one of the first things i have done to my Jimmy back in 96 and now has around 365,000 miles and still original parts. I have just been servicing the transmission every 80,000 miles and replacing the Boost valve every time i service the transmission. Here are the things i have done to my 4L60E in my Jimmy.
1. Boost valve replaced every transmission service 0.490" size boost valve. (10 min to install, must drop the oil pan)
2. Swap out Servo with Corvette servo. (45 min to install)
3. Installed B&M ShiftPluse electronic shift improver. (15 min to install)
4. Add B&M secondary transmission oil filter, (20 Min to install)
These are just the simple things that i have done to my transmission and also changed my shift points with my HP tuner. (HP Tuner does not support 96-97
have to use the 98 ECM with 2001 program FYI)http://www.gmfullsize.com/forum/showthread.php?t=98029
http://www.bmracing.com/SPECIALS/ShiftPlus-electronic-Shift-Improver-for-GM
As for your transmission Jumping by 200 RPM, it's your Torque Converter locking and unlocking. To many things that can cause your Torque Converter to lock and unlock, but most likely electrical issues. Inspect your TPS again to make sure it reading are not jumpy, inspect your brake light switch under the dash by the brake peddle arm. Last have the transmission line pressure checked, put a transmission gauge (or Visit a transmission shop) on the pressure test port and go for a drive to verify proper line pressure. Base pressure at idle in P,N,OD should be around 70psi and around 140psi in R. Max line pressure should be at least 190psi at WOT in 1st or 2nd, 225psi is optimum. If base pressure is low, trans or pump is worn out. If max pressure is low, check EPC solenoid. If reverse is slow to engage, and line pressure does not come up to at least 130psi in reverse, replace the boost valve with a Transgo 0.490" boost valve (easy fix in pan).
Keep me posted and keep up the great work.