2003 Cobra issue...
 

My 2003 Cobra has a rough idle. First off, the car is as stock as can be aside from a Steeda CAI and Steeda Catback. The best way I can explain it is that I start the car and what seems like once every other rotation the car misses so there's a noticeable odd jerk through the body. I chalked it up to possibly a dead ignition coil, spark plug or in injector.

I decided to inspect those three parts and obviously started on the drivers side head because it's easier lol. Looked at all the coils, spark plugs and tested for a misfire with a NOID light. Well everything looked fine until I hit the passenger rear coil. I pulled it out and it had a lot of what looked like dried anti freeze on the rubber boot. Like a chalky whit/yellowish residue. Well I figured I was on to something and dug deeper. When I pulled the spark plug out it was wet. It was covered in what I can only describe as condensation. It was crystal clear water. I'm assuming this could be the cause of my problem. I haven't replaced the coil or spark plug because I figure it'll just do it again.

Anyone have any thoughts on this? Head gasket leaking anti freeze? Should I not be driving the car until this is fixed? (Note: I've been driving the car for 5-6 months in the state that it's in)

Luckily I can hop into my Mach 1 and drive it while I (possibly) tear down the Cobra to find the problem.

Thanks in advance for any advice.

Sounds like a blown head gasket. Check the oil to see if there is any coolant in it. You can also check the radiator/coolant reservoir to see if it has oil in there.

I assumed the same but I can't find any traces of oil in the coolant or vise versa. Plus the liquid on the plug was absolutely NOT coolant. I'm quite puzzled on this one.

Would compression be affected by a blown head gasket?

Are there any tubes around that plug?

Swap the coil and plug to another cyl. and see if the symtom follows the coil and plug or stays with the cyl.

If you have the means to do a compression test, i would do one. It will least give you peace of mind if everything checks out ok. You could do what TUFF 4.6 said or just try replacing all the plugs. I would have assume the check engine light would have come on if there was a problem with the plug and/or coil.

go for the compression test. You can get a tester at autozone for 25 bucks and mine has come in handy many times. In the instructions for the tester it tells you scenarios with the compression and what it could mean. If you have a blown head gasket, usually two cylinders are off in compression. Try draining the oil and if it comes out looking like chocolate milk, then, that's a blown headgasket for ya :-(

Any check engine lights?

Replace coil and all plugs(just cause) and see if it gets better. I am banking on a dead coil/plug being the ONLY problem.

Thanks for all the suggestions everyone.

Here's the latest findings...

Compression test showed no problems. The other day my check engine light came on and threw a few codes all in the P0300's, Misfire on cylinder #6 and misfire on cylinder #6 during first 1,000 rpm. I'm going to change out all the plugs and the #6 coil. Hopefully this fixes it.

Cross your fingers for me that this fixes it. I'd rather not tear the head off.

-B

Are the cylinder numbers the same on an '03-'04 cobra as they are on a '01 Cobra/Mach 1?

My car threw a check engine light and spit a misfire within the first 1,000 rpm and a general misfire on cylinder 6.

Is cylinder 6 the second cylinder back from the radiator on the drivers side?

If not, which one is it? I have the damn Ford Service manual that's like 2,000 pages and I can find the torque settings for the most insignificant little bolt but I can't find which cylinder is #6 lol.

Keep your fingers crossed guys and gals, I think this is just a bad coil.

P.S. is there an easy way to test coils? No auto part stores around my house sell anything that I can test a coil with.

Swap the suspect coil with another and see if the missfire goes with it

the only way to test a coil is to check the resistance of the windings. just hook an ohm meter to both terminals. youll have to look up the specs for it