My 05 C2 has been experiencing some issues. First it started out with leaking coolant so I replaced two lines which fixed it. Then I started having low coolant again but at a much less frequent pace (likely expansion tank). I went on a drive and topped off coolant before. As I was leaving I got what felt like a few misfires but they went away. As I arrived at my destination there was coolant gushing out of the expansion tank (probably a gallon in a minute or so). I let it cool, topped it off and drove home carefully. During the drive back I got the misfires more constantly as well as another low coolant warning (didn't fill it enough I guess) and after topping it off again I didn't have any issues for the drive home (either with misfires or low coolant). I let the car sit for a week and started it the other day which resulted in a large puff of smoke upon start, constant misfire/CEL. I cleaned the MAF, throttle body, and disconnected the battery for 20 minutes to try and reset any codes but to no avail.

The only mods to the car are a cat delete pipe, fabspeed intake (just the hose), and the shop had raised the o2 levels to avoid a CEL because of the cats.

Im pretty worried about the car hoping it isn't anything serious. The only thing I can think of is a coolant expansion tank and coils but the car just had a 60,000 mile service a few months ago so I couldn't imagine they would have put cracked coils back in or that they would have cracked in the last 2,500 miles.

Any ideas???

 

Coolant leaks are dangerous if they are at that fast rate. I would've towed the car to a shop to get the expansion tank replaced.
The misfires are cracked coils. If the coils are brittle and when you put them back, you will crack them and the coolant leak will travel to the coils creating the misfire.
Replace the tank, flush the system and replace the coils. Then use PIWIS or Durametric to clear the codes and report back. I think that will solve your problems...

 

Good luck...let us know what happens.

 

The coolant leak wasn't fast as after I topped it off I drove 100 miles back and another 15 to the shop before it read low again so it wasn't hemorrhaging coolant.

 

What scares me is the white puff of smoke after starting... you either have an Oil Separator going out at the same time or something else..

 

I never said it was white, just a puff of smoke. It looked like oil and condensation to me.

Hopefully..

 

Good news!

The coolant cap was faulty and causing fluid to leak onto the coil of cylinder #1 which was causing the misfire.

 

That's awesome news man...happy for you!!