I have a 96 sl2 and when the electric cooling fan comes on it bogs down the engine very bad to about 400 rpm. Then it seems that i get P0304 code after that. It also seems to do it if i use the electric windows. Is it possible the alternator is going bad? The car never fails to start and seems to charge just fine. The car also idles very rough. Any well would be appreciated.

 

battery weak, unable to hold charge, or alternator not charging it

 

my guess would be alternator. if your car does not ever have trouble starting, then it would not be the battery. the starter is fairly demanding, for a second or two, on your battery, so it will not start if the battery is bad. if the alternator bearings are going, when you put more load on the alternator, it will bog down the engine. also this could cause your rough idle, as the normal demands that your car puts on the alternator are enough to put some force on those bearings, causing it to put more strain on the engine. take the alternator to a local autozone, and have them test it. i believe it should be putting out about 14v or so. however, the electrical component of it could be fine, leaving just a seized or worn out bearing. it is possible to rebuild alternators, but it's not too easy to find parts to do that these days.

 

Just a question here -- does the engine "bog down" when you turn on the headlights during the day?

 

that's funny, I thought alternators output current, not voltage.....

 

They do, but since the amount current that every alternator puts out is different, it would be impractical to test amperage. at the same resistance, voltage and amperage are directly proportional, so if not enough current it being put out, the voltage will have dropped.

 

Ok I continue to get a P0304 code. I have replaced the wires, plugs. Still does it. I then switched the coil packs around just to see if maybe the coil was bad... no difference. The weird thing is when i accelerate the car does great no missing or anything great power, but it idles horribly and is even worse when i put it in gear. I pulled the plug wire off #4 and it sparks very good. Pulled the plug hooked it back to the wire and it sparks very good. I am certain it is missing as you can hear it in the exhaust and see it in the way the engine shimmys. Is it possible that #4 has bad compression and that is why it idles bad then when the RPM come up it smooths out? Could a bad intake gasket be giving me this same symptoms. I did spray starting fluid around the intake and the RPMs never increased. The car only has 113,000 miles on it and i can't imagine it's shot, but my frustration is increasing quickly and i am thinking i may need to buy a new car!!! HELP!!!!!