Sudden misfire and electrical smell

Post by **tom39** » 05 Oct 2021, 06:43

2011 Volvo S80 3.2l 153k mi

This morning on my way into work (11mi trip), at mile 4 I suddenly I felt the motor begin to stumble, lose power and there was a pronounced vibration at acceleration. My first thought was that I dropped a cylinder (bad coil or plug) or bad gas (but I was at 1/2 tank and had no problems running through the first half).
There were no CEL displayed on the cluster and I was able to limp it the remaining distance to work. Once at work, the following are things that I observed.

1. Sputter sound at exhaust
2. Slight hint of electrical smell under the hood
3. Flickering of interior lighting
4. 22.4vdc at the battery terminals
5. Also, there is an odd exhaust smell but I am attributing that to the running rough issue.

My first guess would be the voltage regulator on the alternator and that it has failed and has the spiked the voltage instead of dropping it out. But thats just an uneducated guess.

Thanks in advance for your help

Tom

Post by **RickHaleParker** » 05 Oct 2021, 19:47

tom39 wrote: ↑05 Oct 2021, 06:43 My first guess would be the voltage regulator on the alternator and that it has failed and has the spiked the voltage instead of dropping it out. But thats just an uneducated guess.

A unregulated alternator is the only possible source for 22.4V. My concern is how much of the wiring and electronics got fried. Tow it home or change the alternator where it is.

You could try disconnecting the battery B+ from the alternator and driving it home on battery power only. Preferably in the daytime so you don't need the headlights. If you have Daytime running light disconnect the headlight bulbs. Turn off everything electrical you don't need. That would give you a better chance of making it home before the battery goes dead. If you have a spare battery take it with you fully charged. You can swap them if the first one goes dead.