The car is a 97 dx (stock y7 with 200k) and I can't come to a solution here... There is no check engine light btw. We tried spraying all the vacuum lines with a bottle of water and a tiny bit of soap with the car on at operating temp to see if any bubbles would form. Nothing. We had to take off the throttle body and IACV anyways to get rid of a sticky gas pedal, hooked everything back up, so nothing there. But the car however does have a good size crack, about 2" long, very thin, between the middle runners where they all meet above the cat. Can this cause a bouncy idle? The car doesn't have a tach so I can't say the range it's bouncing between but I can say it only does it in park and neutral, not in drive or any other gear.

Any input? Thanks in advance.

 

Yes. Replace it.

 

A cracked header would only cause back fire's from the mixtures of o2 and gasoline fumes. Let your car warm up then turn it off. Unplug your iacv and turn your car back on and see if the idle went down. If so drain your coolant, clean iacv, make sure the gasket to your throttle body is not letting in any air, refill coolant, burp coolant.

 

We cleaned the IACV, TB, gasket, and mating surfaces. Everything appears to be nice and tight and isn't having any leaks.

It's my friends girlfriends car and he plans on buying a new header for it at some point. He just wants to get it running a little better to be able to pass inspection (just got it, temporary inspection).

Thanks guys.

 

I thought 96 and and up did not have an IACV?

 

I believe it's: 96 and up have the IACV but not FITV.

 

Yes, All engines need some backpressure to operate properly the crack will significantly reduce it.

 

I had a similar problem with just a break in my test pipe. caused my idle to be all over the place but mostly higher. If you have played with the throttle cable and timing then ya back pressure is good deal.