I recently changed the stock throttle body from my d16y8 to a 70 mm one changed tps and iac valve, my problem is that it’s idling super high and then it surges up and down then when i press the gas it starts stuttering doesn’t let me pass a certain rpm, a while back it threw the “cattalytic past its threshold” code, could the cat be the culprit? Or the aftermarket iacv?

 

Any help plz I need my car running

 

Did you adjust the TPS? iacv has 2 coolant lines running to it, possibly needs to be bled.

 

yeah I adjusted the tps but throttle closed the lowest I could get it to go was .52 and WOT 4.48.
there’s a little screw on the iacv my little brother unscrewed it (by accident) would anything happen if that gets messed with?

 

Make sure the TB gasket is on properly and the right size. And make sure the TPS is installed correctly before adjusting it.

 

Put the stock throttle body back on. A 70mm is WAAAYYY too big for a D16Y8 and a stock computer will never be able to idle the car right. You will have to get a tuneable solution... and even then, all you will do is lose power in the mid-range and gain little or none at or near redline.

 

My thoughts as well, the step from the small inlet in the manifold or not port matched will hinder performance. Slap the stock one back on like JRCivic1 suggests!

What was the reasoning behind such a big TB?

 

would it cause it to throw the p0505 code after erasing it?

 

It depends on how long it takes for the code to return.