916stang

Hey guys, new here. I just recently replaced the intake manifold for a cobra one and the TB with a 65mm one and it has developed a problem. When I start it, it starts fine. It will stay on for a few seconds and just cut off.

Things I've done:

Check for any vacuum leaks
Checked for tb gasket leaks
Replaced most of the ignition system
Checked timing.

Yet still nothing. If I press on the gas it revs just fine but wether I'm stepping on the gas or not, it just shuts off.

Here is a video of it



If you guys can help me out. I'm not sure what else to do/check.

Thanks

dawson1112

Damn that's almost like someone flips the off switch lol . And it will start right back up ? All you did was swap the intake and throttle body out?
It almost acts like the computer is shutting off the spark .

916stang

lol yeah i know it seems like someone just shut it off and that's all i swapped out was the upper and lower manifold it does start right back up but it just shut off within a couple of seconds

dawson1112

When it dies out like that leave the key in the run position and check for 12v at the coil. I believe its a red wire with light green trace.

dawson1112

After you confirm 12v at coil , get some starting fluid and have someone spray it into the intake while its running and keep spraying it until it dies see if it will run longer. It will run crappy if it stays running , but if it stays running Id say your fuel pump is crapping out on you or you have a pinched fuel line.

916stang

When you say spray your intake you mean around it? Cause I've done that to check for leaks and the coil is brand new I just bought this week

dawson1112

It doesn't matter if the coil is new Im trying to find out if your loosing your 12v feed to the coil from the ignition when the key is on.

And when I say spray starting fluid into the intake I mean take the air cleaner off and have someone spray it into the throttle body while its running to see if its loosing fuel . If its loosing fuel it will stay running while the starter fluid is sprayed into the throttle body, as soon as the spray is gone it will die.

LCBlackDep183

That's so sudden. Odd.

When you start it do you have the hold the accelerator down the whole time?

916stang

no i dont have to hold the gas down it turn on perfect and then just dies

Mike T

Turn the idle screw up a little and see if it helps.