Boost leak at IAC?

[ruthless]

I am having a slight issue that I hope someone can help me with. My car wasn't building boost at the track (76mm custom turbo kit with an 01 Cobra intake manifold.) and after some testing my buddies and I found that the gasket between the TB and the intake was pushed out because of one missing bolt and the other only hand tight. Yep that's an oops. So after fixing it I made another pass and the boost was great at first then it kinda fell off during the run.

I got the car home and used a setup that allows me to pressurize the intake system so I can find boost leaks. I had it from when I had a dodge stealth with 2 miles of piping under the hood. lol

Everything tested good on the cold side piping but when I went to pressurize the intake manifold I found a leak coming from the pressed on cap of the idle air control valve. I am not sure what is going on but it leaks so bad I can do a test. If I pull the valve off and plug the two ports everything pressures up fine.

It my IAC bad and causing this massive leak? It is leaking if I even blow into it from either port with the other blocked off. I am thinking this vent is so the valve can move but a seal of some kind inside bit the big one.

BTW I am only trying to run 16 to 17 psi. I am sure if I tried 20+ that little pressed on cap would blow off the IAC.

 

[ruthless]

I was just looking. The IAC on the car is for an 01 Cobra. The 03 Cobra has a different part number. What one should I be using?

 

[xXAzureMach1Xx]

IAC is bad. There isnt a vent. Air leaking from the IAC valve is unmetered air. You'll need the one from 01 cobra. They are both the same but the plug angle is different.

 

[ruthless]

I agree. Just trying to understand why the breather is there on the 01 cobra style but not the 03-04. Seems like the valve has I rubber diaphragm of some type and the little vent allows the valve to move ?

 

[ruthless]

Well I talked to the shop and they were not very helpful. More or less told to buy a new one and see. :fm:

 

[xXAzureMach1Xx]

Buy a new IAC. It shouldn't be leaking air. I don't see why there would be a vent either. Valve is there to let metered air past the tb to idle at a set rpm. Buy a 03/04 mach iac. No "vent" and same as 01 cobra.

 

[ruthless]

Buy a new IAC. It shouldn't be leaking air. I don't see why there would be a vent either. Valve is there to let metered air past the tb to idle at a set rpm. Buy a 03/04 mach iac. No "vent" and same as 01 cobra.

I wish I could find the IAC from when my car had the twin screw. :fm:

 

[HIPSI]

That iac you have sucks in unmetered air,couldn't figure out why I was having problems it was the iac ,purchased 1 from 03 cobra it has no air bleed .fixed my lean issue.

 

[ruthless]

That iac you have sucks in unmetered air,couldn't figure out why I was having problems it was the iac ,purchased 1 from 03 cobra it has no air bleed .fixed my lean issue.

I ordered one yesterday. :banana: The thing that is driving me crazy is that the car drives perfect, I just cant get the power I had because the more boost I force in the more this iac is bleeding off.

 

[ruthless]

The new 03-04 Cobra IAC arrived and doesn't leak air/boost at all. :banana:

Thanks for all the help and listening to me cry. lol

 

[HIPSI]

The new 03-04 Cobra IAC arrived and doesn't leak air/boost at all. :banana:

Thanks for all the help and listening to me cry. lol[/QUOTE. Runs better don't it?

 

[ruthless]

The car ran fine out of boost before but when I got on it I wasnt building the boost I should have been on the settings I had on the AMS-500 boost controller. Prior to the leak I was hitting 17 ish psi and after the issue started I was at 10-11.

Unlike other boost controllers the AMS-500 unit I am using and AMS-1000 monitor pressure applied to the wastegate and dont care what the engine is seeing boost wise. So if you are using Co2 and tell the controller to put 12lbs on top of the wastegate it will no mater what boost the engine is seeing. So with my setup of a 2.8lbs spring in the waste gate with 14psi of Co2 on the top port I was seeing 16-17psi at the engine before the leak started. After the leak the boost controller doesnt automaticly adjust so I end up seeing less boost.

I did turn it up a few clicks to test and wasnt seeing the increase that I should have so I knew something was up. Then the test I ran on the intake showed the massive leak at the back of the IAC. However I wasn't sure if this port always leaked or not because this was the first time I tested it. Guessing from experiance with other turbo vehicals told me this wasn't right. My TT Stealth would hold enough boost to let me test for cold side leaks but I couldn't hold 1psi with a big air compressor on the cobra.

 

[ruthless]

I installed the IAC and ran into a slight issue but was able to correct it. Since I run a spacer under the intake lid and the 03-04 Cobra IAC has the connection pointing straight up, the connector was hitting my hood when it ws closed. Luckly I was able to cover the motor of the IAC with tape and use a big pair of channel locks to twist the motor so the connector points back like the 01 Cobra unit. (Mach1 IAC maight be setup this was but I found the 03-04 cobra unit cheaper) I am just glad it didnt cause a problem.

I started the car and the rpms where a bit high (1200rpm) then I could see the computer making adjustments as the engine warmed up. After I did this I started thinking that maybe I should have disconnected the battery to reset the computer. Oh well its ideling fine (in the 900s) and now I just need to take it out and see if the boost issue is resolved.

I did notice differances with the ICA units. The 01 has that vent on the back, a rather large motor, and when you look inside the ports at the valve assembly you see a shaft that runs by both ports with a spring on the far side away from the motor.

The 03-04 setup doesnt have a vent/breather port for the diaphram, the valve only has the shaft on the one port closest to the motor and no spring.

Just thought it was strange that they are so different but do the same thing on the same car.

 

[ruthless]

I had the car to its first flashlight drag race since replacing the IAC and putting the boost controller on C02. The car seems to be running better with the new IAC but it took a bit to get the boost controller settings back to where I wanted it. The AMS-500 of C02 holds its set boost pressure like a champ. :rockon:

 

[Joyrider564]

I had the car to its first flashlight drag race since replacing the IAC and putting the boost controller on C02. The car seems to be running better with the new IAC but it took a bit to get the boost controller settings back to where I wanted it. The AMS-500 of C02 holds its set boost pressure like a champ. :rockon:

It is a simple but effective boost controller. Where do you have your CO2 bottle setup?

 

[ruthless]

The bottle and regulator are in the trunk. I used the hard plastic hose and metal push lock fittings to connect everything together.