Vacuum Leak or IAC issue?

[SvtCobra0404]

hi there, I have a 2004 cobra with the following mods.
Off road x pipe
Catback exhaust
Cold air intake.

Once the vehicle is driven and warm it gives me a small idle surge. I’ve used carb cleaner sprayed the lines and gaskets to check for a vacuum leak but cannot find one. I installed a vacuum gauge and measured vacuum and it stays at 21. Can this be a bad idle air control valve or tune related?

 

[SvtCobra0404]

The idle surge only happens after I take it out for a spin. Today I left it to idle got it to operating temp. Still no change in idle. But when I press the brake really hard the idle moves a little and vacuum gauge reads 20 from 21

 

[01yellercobra]

The brakes get their power boost from the power steering pump. That's why the idle changes when you press the message pedal. You could try cleaning the IAC and see if it gets any better.

 

[SvtCobra0404]

The brakes get their power boost from the power steering pump. That's why the idle changes when you press the message pedal. You could try cleaning the IAC and see if it gets any better.

I have tried cleaning IAC before but didn’t change it. I’m considering replacing it with a oem one and new gasket for it?

 

[01yellercobra]

I should've asked first, has it always done this or is it a recent development? If it's a recent development then the IAC could be bad. One way to check is to unplug it to see if the idle gets better. Provided your throttle stop is adjusted to allow it to idle with it unplugged. If it's always surged I'd talk to your tuner.

 

[SvtCobra0404]

I should've asked first, has it always done this or is it a recent development? If it's a recent development then the IAC could be bad. One way to check is to unplug it to see if the idle gets better. Provided your throttle stop is adjusted to allow it to idle with it unplugged. If it's always surged I'd talk to your tuner.

It’s recently developed it. Didn’t do it before. I will try that tomorrow.

 

[Kingcobra2fast]

I had these exact issues of not running right, dying at return to idle, missing, fouling plugs and upon supercharger removal found a kinked PCV line from underneath side of intake causing oil to spray in the valley and leak all over everything. I thought i had a bad seal in the motor so this was a great discovery. This was also disrupting tbe idle due to the caused vaccum leak from the stretch and bent pcv hose that had lost its seal from being on the nipple all ****-eyed with uneven pressure on the hose. No clamp on the pcv hose on the lower intake. The line just slides on the nipple. Someone just stretched the line to plug in the back of the supercharger. I also had some header leaks that didnt help out the Idle and was probably the main cause of why my plugs were failing in cyl 3. but i wonder how many people just think the stock pcv line will be ok stretched to plug into the back of an upgraded supercharger. Hope this helps. I have been troubleshooting my iac and any other test u can imagine to find a reason for poor idle . Its been a long road. Im just getting the k member and suspension put back together. I guess ill know when i fire it up what benefits will come from the solutions i have made

 

[SvtCobra0404]

I should've asked first, has it always done this or is it a recent development? If it's a recent development then the IAC could be bad. One way to check is to unplug it to see if the idle gets better. Provided your throttle stop is adjusted to allow it to idle with it unplugged. If it's always surged I'd talk to your tuner.

I unplugged the IAC and the car stalled after a few seconds. What does this mean?

 

[thatdude305]

hi there, I have a 2004 cobra with the following mods.
Off road x pipe
Catback exhaust
Cold air intake.

Once the vehicle is driven and warm it gives me a small idle surge. I’ve used carb cleaner sprayed the lines and gaskets to check for a vacuum leak but cannot find one. I installed a vacuum gauge and measured vacuum and it stays at 21. Can this be a bad idle air control valve or tune related?

I had a similar issue and my mass air was touching the cai, that was the issue

 

[SvtCobra0404]

I had a similar issue and my mass air was touching the cai, that was the issue

What do you mean by it was touching the intake?

 

[Kingcobra2fast]

I assume you have tried draining the power from the computer on each attempted fix when working with electronic sensors. ??

 

[SvtCobra0404]

Nope I did not. What is usually the procedure?

 

[Kingcobra2fast]

Well it resets the learned memory from your old IAC to give the new piece of technology a chance to do its job and get the readings for the idle vs stored idle readings from a possibly faulty IAC that was previously installed.

 

[thatdude305]

What do you mean by it was touching the intake?

The wires were touching the CAI pipe and it would heat up and stall the car

 

[NGO]

I had this issue- idle would go from 700 - 1000 RPMs, worse when A/C is on. Replace the IAC, fixed that issue but now when I first crank it up the idle jumps to 1800 RPM for about 3 seconds then comes down to 900 RPM. I am hoping it is just due to the computer learning the new IAC.

 

[01yellercobra]

The wires were touching the CAI pipe and it would heat up and stall the car

Is your CAI metal? If it's getting hot enough to cause issues with wiring you had other issues.

 

[thatdude305]

No my issues are fixed now, just a simple adjustment