Intake swap!! Now car is running rough!Help

[Bobafett123]

Ok NowI have searched through the threads and just cant seem to find an answer for this problem. I just completed an intake swap upper and lower intake going to the GT40 lower and a original 93 cobra intake upper. Every thing is completely buttoned up and we have no leaks of any kind but the car (92 gt) is not wanting to idle at all and its running rich. We had some Code issues that we went through and got fixed, we also pulled the Dizzy and put it back in and reset the timing but it just wont idle and it does have some back firing through the intake ? Can anyone help ????

 

[mob]

I would hook up a vacuum gauge to it to make sure you dont have any leaks in the lifter valley. Check for vacuum at oil filler cap or dipstick.

 

[87GT40]

i agree. if you can try to find somewhere that has a smoke machine to search for a vacuum leak also.

 

[68stang351]

I vote for vacuum leak also. That's what it really sounds like.

 

[the pony boy]

timing.do a searech on top dead center. good luck phil

 

[Bobafett123]

Went through and did the standard starter fluid check over the motor fo a vacuum leaks and we could not find any but I totally agree that it is acting like a vacuum leak . I am going to go over all the connection and check around the valley. Is there a better way to check for vacuum leaks near the valley?? other then getting to a shop to get a smoke check done ?? Also does anyone have a nice picture of the underside of an orignal 93 cobra intake ?? The only pictures I can find on a search is based on the Chinese replica from Ford Racing .

 

[tiptopss]

yep, 1 of 2 things, timing or vacuum

 

[Mustang5L5]

Which gaskets did you use?


Get some carb cleaner and spray around the lower intake area. If the RPM's rise, you have a vac leak

I found that some of the gaskets don't seal well where the heads are. I had to go with the Fel-pro 1250's after finding the normal HO gaskets causes a small vac leak.

I think that day i yanked and installed the lower intake 4 times in about 2 hours!

 

[Bobafett123]

Well you guy were right Vacuum leak in the back of the Cobra intake . I found that the guy I bought the intake from when taking it out must have pull out one of the vacuum line nipples and there was a nice hole in the backside bottom of the unit . I knew it was there talked to my brother in law who was doing the bulk of the work on the swap and we forgot to plug it when we put the upper back on !Thanks to everyone for the Quick Help !!!