Misfire after jump start/drained battery

[chrisinthecouv]

Here is a run-down of the how my s40 got to where it is:
- Car was starting/running fine - no issues
- Used s40 to jumpstart another car I was looking to buy. Accidentally crossed the jumper cables on the car I was jumping. Completely drained the battery on my s40. Was able to jump start the s40 and get it running. Didn't appear to be any problems.
-The next few days the battery had a difficult time holding a charge. I had to put it on the charger several times. After a few attempts it was mostly charged.
- Then it suddenly started becoming difficult to start and running poorly. It feels like it has a serious misfire. Sometimes it will start, and if it does, it runs terrible.
- I pulled each plug and each one had spark. Plugs could use a change. Been a few years...
- I could smell gas on the plugs and coming from the cylinders so I'm assuming I'm getting enough gas.
- I did a quick check of fuses and relays and didn't see anything that appears blown.

What could be causing the starting difficulties and misfire? Did I fry something when I hooked the cable up wrong? Coil packs? Relay? Other?

[alschnertz]

Try a different battery.

[chrisinthecouv]

I changed out the spark plugs. Was able to get the car started. Here is what I noticed:
- engine still misfiring/running rough
- oil is becoming milky/tan looking. Some small air bubbles appearing.
- heavy steam coming from the exhaust.

Looks like I have a blown head gasket to fix. I have a Haynes manual for the car, but would also like other advice. Can someone point me to a post for this, or give me pointers?

thx!!

[alschnertz]

Wow, a blown head gasket from crossing the jumper cables. That's a new one.

I've found the S40 Haynes manual to be ok. Not great, but at least it's something.
Last I checked (maybe 1-1/2 years ago) it was the only repair manual available.
Search will be your friend. You can also search that repair on the 5-cylinder models of that era. It's a very similar engine.