5.0 Cobra intake swap made my car slower???

[67coupe]

Check your vacuum lines around the EGR valve. Make sure the vacuum source for the valve is the correct one. If you are using constant vacuum for the valve, it would give similar problems you are describing. At idle, the EGR valve should have no vacuum and be closed.

 

[91foxbodygt]

when we put the injectors we replaced the o-rings, thats why one of the injector tips broke. they were super dirty. anyways, they fit tight in the stock intake, but with the cobra, they were kind of loose, actually if it wasnt for the fuel rails holding them in, i wouldnt trust the 19#'ers on the cobra.

 

[fastest stock 87 gt]

just a thought on your timing i really dont think anybody runs 10* of timing on a mustang anymore. that is the factory setting. usually most people run from 12-14* unless they are using power adders.

 

[91foxbodygt]

well i was hearing under the hood, listening for a "ssssss" sound and disappointingly thats what i heard. at first i thought it was the header gaskets, but i remembered they are new. the sound is heard around the upper intake. im guessing its the vacuum leak all you guys told me about.
many thanks to all of you, your post were a lot of help

 

[Paul Perreca]

well fix the leak n go get new ET's cuz i wanna know how much of a difference it makes - thanks dude good luck -
Pauly P

 

[criticman]

Bringing this back up for two reasons...1, I want to know where the leak was exactly and if he regained power and 2, I am having same problem.

Mine isn't nearly as bad. The power is there, lost minor low end torque, but top end is a lot stronger.

BUT, it idles harsh (no matter where I adjust the idle to - properly I might add, IAC controller off, ECU reset, etc) with TPS reading 0.989 (suggested I have read is .98 to .99, so I am dead on), all new gaskets, new o-rings/pintle caps on injectors (I too felt they went in REALLY easily - but lubed them slightly as advised in other threads). I made sure all hoses are secured...apparently I had a hose snapped on stock upper to the charcoal canister...replaced it when doing swap to avoid leak.

So, what else is there to check? Like I said, idles harshly, harder start than before. Any pointers are appreciated.

 

[GREYFOX4INCH]

I Jst Gotta Say I Dissagree, I Run A Cobra Intake With Stock Heads And Have Increadible Low End, I Know I Know 4.10's.but Any Part You Trow At Your Car Is Gonna Give You More Top End, A Cobra Wont Kill Your Bottom End Completely Either!
(hey This Is A Real Stupid Question But....)
When You Did Your Timeing Did You Remember To Put Back The Little Jumper Plug That Your Suposed To Unplug,that Will Kill A Second In 1/4 For Sure, Not That I Have Done That Or Anything ::cough::
Easy To Forget If Your Anxious To Test Your Car. Im Mean The Timeing Is Like The Final Step Before You Get To Beat It.right?

 

[85mcLaren]

make sure your vacuum for your egr is correct, otherwise the valve may be opening with constant vacuum.