Rough idle after headers installed

Yesterday I had replaced my cracked manifolds with a set of Fabspeed headers on my 05 F430. I drove the car about 20 miles when I noticed a very rough idle. When I pressed the throttle, there was hesitation, but it smoothed out at about 2k. I am taking the car back to the shop on Tuesday, but until then, any ideas on what may be going on?

 

Exhaust leak making a lean condition

 

Yes double check for leaks and did you get your ecus tuned?

 

I will be doing the ECUs in about a month. I am waiting for my exhaust to show up.

 

When you say you replaced your cracked manifolds, do you mean you personally ir this shop you mentioned? Either way, sometimes the stud nuts need retightened after the first drive or two. Also, recheck the 4 O2 sensors. Finally, was antiseeze compound used?

 

Could you please elaborate on what you mean “you personally ir this shop you mentioned”? I am not sure if they used antiseeze. I will be asking the shop these questions when I return it.

 

Did you drive it just that once?

 

See if they installed new donut ex gaskets between the headers and cat pipes.


I tried to reuse mine and they were too compressed and cracking so I had an ex leak in this position.

If you can scan you car… you can better diagnose the issue. Was it caused by install? Or something failed at same time?

if shop does not have a scanner then they might have trouble.


I use obd facile, it scans both banks

Check for codes and lt and st fuel trims.

Gl

 

First off did you check the flatness of the new manifolds with a straight edge before they were fitted, if so then try a thin feeler gauge between the head and the manifold to see it is compressing the gasket. Fitting this sort of thing you need to be checking with feeler gauges as you nip it up. After that gas tightness of sensors and donut joints into the cats are next