As the weather started warming up this year, I started having problems with my car idling. The problem first manifested itself by dying as I came to a stop at stoplights or even a few times when I would coast with the clutch in. I usually didn't even notice until the red battery light caught my eye, and I realized it wasn't running anymore. The problem seemed to get more frequent. I changed my coils and the problem persisted. One time while I was cruising about 80 on the interstate, I got a few misfires. I couldn't feel anything (except some power loss), but the light was flashing. I changed my plugs and plug wires, and that seemed to fix it. The car seemed like it idled better and I went over a week without the problem happening again. Wednesday, the car died on me as I stopped at a stoplight. The car did not start back up even though the starter turned (albeit slowly). I'm not really sure where to go from here. I've searched for vacuum leaks (didn't find any). The idle speed fluctuates when the ac compressor is on. When the clutch engages, the car will bog down to roughly 750 rpms. When the clutch kicks off it will ramp up to about 1000 rpms. It equalizes around 850. The problem does seem like it could be linked to the ac compressor bogging the engine. I recharged the ac system thinking that could be related to the problem, but that made no difference. When the ac compressor kicks on and bogs the engine, the voltage can drop into the twelves before returning to roughly 14v. At idle speed, the voltage across the battery is roughly 14.2v. With the car off, the battery voltage is roughly 12.4v. For the most part, the charging system seems like it is working fine. Last night, with the car nice and hot, ac on, fans on high, and headlights on, the car was only maintaining 12.6 ish volts across the battery at idle speed. That makes me suspect some alternator trouble, but for the most part the charging system seems fine. I have not been able to recreate the conditions to make the car die while testing it. Wednesday, when the car died, it did have a full tank. So that makes me think it is probably not the fuel system. I've done a decarb procedure with some sea foam with no change in behavior. Car has 147k on it. Engine has roughly 44k. Any suggestions would be greatly appreciated.

 

This exact thing was happening to me last summer down to the letter, albeit in a different car. It wound up being a faulty alternator, specifically the connector to the alternator was completely sheared by something which damaged the alternator itself.

 

How's the compression?
It's not the only possible explanation, but its sort of a big one.

 

I haven't had a compression test done yet. I've never had hot start issues until this started, though.