I pulled it out of the garage yesterday and parked it in the drive way. Was running a little rough/funny but it was extremely cold. Go to fired it up later and will not start, cranks strong no start. Found a cracked ignition coil, replaced with new along with rotor and cap. I now have spark but no start, even dumping starter fluid in it I have no start. I can't think it lost compression literally over night? Been running great with super good gas mileage. Stumped. Also double checked timing and everything lines up. Again compression is about all that is left but how?

This post has been edited by Agent21: Feb 16, 2015 - 1:26 PM

A 5sfe motor will not start without enough back pressure. Mine has a racing header so no cat. If the seal at the collector is bad enough the motor will not start and simulates low compression. This has happened twice.

Could be you're not getting fuel, I wouldn't think all four injectors would go at once so I'd look at the pump and pressure regulator. That or with the regulator you're getting too much fuel and it's flooding. Another thing would be maybe the IACV is seized, have you tried starting with the throttle plate opened? I would check into all of that if it were me, that and any related fuses.

Nah I got it fixed. Sealed it back up at the collector flange to the exhaust pipe and after pumping all the starter fluid out it finally fired back up and has been fine since. My only guess is that the leak was screwing up the o2 sensor? but that shouldn't factor in until after ignition or the lack of back pressure was some how messing up the harmonics?

At least it was something simple. It's weird though, because I want to say I've seen a video or two of people running it with an open header just for lols before completing the exhaust.