My car idles funny, goes 800 then 1800 rpm then back down, etc.... does it when the car is warm or hot! No CHECK engine lights codes! Car is fine in boost....

I reset the ECU and it idles fine...then a few moments later...bam same thing happens...Here's the story:

I got a new STR Manifold. Everything is hooked up correctly...except for the sensor on the BACK. I believe its the IACV. It has two water hoses going into it and it has 2 holes...one that reads manifold pressure, and the other one, i'm not sure what it is?

Anyways, on the STR Manifold where throtte body and manifold mates, there is the 64mm hole and there is SUPPOSE to be another hole for the throttle body hole thingy (Air from before the throttle plate) but on the manifold it does not have that! That hole provides air or something for that Sensor (The "Mesh" Part) on the back of the maniofld....but now there is non.

However, on the STR manifold, it has this nipple taht sticks out for air to go into that 2nd hole on the sensor. am i suppose to connect that to manifold pressure? (Drill a hole on the intake pipe near the throttle body and weld a nipple there and connect a hose from that to that nipple on the bottom of the str manifold that connects to the "mesh" part of the IACV ) This one guy said to leave it open...

 

can you get any pics at all?

 

I hope this clears some things up! THE IACV (The Mesh Part) is getting no air into it. That might be my problem, but i'm not sure

Heres the bottom of the manifold:


As you can see that nipple part I did not connect it to anything! I have no clue what I should connect it to.

 

the IACV (idle air control valve) is whats giving you problems, where to connect it w/ the STR manifold i dont know.

 

ugh, it's late..the eyes are playing tricks...

sounds like a vacuum leak/sensor malfunction. by malfunction I mean they aren't all hooked up (like you said). everything should be hooked up and/or sealed off on the manifold.

 

If its a sensor malfunction wouldn't I get check engine lights?

I doubt its a vacuum leak because why? When the engine is warm, I reset the ECU and it idles beautifully at 800 rpm...then BAM like 20 seconds later it decides to go up and down between 800 and 1800 rpm.

I think it has to do with that port that is open on the STR manifold. However I'm not sure what I should give it? Should I plug it up or connect a hose from it to the intake pipe before the throttle body?

 

Ok, it has to be something with the IACV, it is not connected properly being that you aren't getting a code. I don't think it's a vacuum leak since it idles fine for a lil bit, if it was a vacuum leak u'd be having more idle probs.

Is there anywhere else you can put the IACV? It must be that, not being connected properly.

Is there any way you can flash that area, or get a better shot? lol, tryin to look at it from that angle, can't really make it out heh.

 

my car did the exact same thing. all i did was buy a new iac valve and that fixed my idling problems