Prius 2005 bad engine misfire

Prius 2005, 246062 miles

This just happened a few minutes ago.

Took my car to go run some errands. 1 minute into my drive the car shook a bit. Drove down hill for about half a mile and shaking got worse, check engine light blinking. I finally decided to go back home and could avoid most of the shaking by driving 25-30 miles/h. As soon as I found the sweet spot the check engine would stop flashing. By the time I got back to my driveway the car was shaking a lot. Stopped the car. Bad smell.
Tried starting the engine again and IMMEDIATELY the engine chokes like crazy. Misfire?

Car was running great this week-end. No sign or issues.

RELATED HISTORY
Car refused to start and was chocking two winters ago but it was -25f so I figured it was something frozen. Next day was -5f and car started like a charm.
Also this winter I backed up in a snowbank and snow got into the muffler and turned into ice. Next time I used the car, it drove for a mile and stalled. But I was lucky and found the blocked exhaust quickly, removed the ice and drove off. No such luck here.

Also a while ago I bought two code readers but for some reason I could never get any codes out of them. Both of them I was told they supported the Prius

CONCLUSION

Now I'm scared of driving the car to the mechanic. I don't want to break anything. Will call a towing if I can't stablize the car.

Spark plugs aren't new. Here's hoping they are the source of the issue. Any way to test without proper tools?

I'm not much of a mechanic so I'm looking for something easy to check (I did change the hybrid battery twice so that I can do but there's no red triangle this time).

No other "bad" lights on the dashboard except "Check Engine" but that has been on for a long time and my mechanic told me not to worry. But seeing it blink today did make me panic.

Was due for an oil change very soon but still have ~600 miles left.

Suggestions? I'd dearly love to save the car. It's a rust bucket but the engine, until tonight, was going strong.

 

Will bring the car to the mechanic today. From my research here and elsewhere it might be an EGR (exhaust gas recirculation) issue.
Hopefully it's not the head gasket...
I don't have the tools to fix this. Also I've broken a few bolts in the past since this car is old. I need someone competent (not me LOL) to do this.

 

Yes it's been raining, but nothing worth mentionning.

I did change the hybrid battery (twice!) and I understand changing spark plugs is not that hard but that's the kind of stuff I let my hometown mechanic takes care of.

Thanks for the EGR tip. I guess my mechanic will figure that one out quickly LOL.

As far as the spark plugs are concerned I had my mechanic change them about 50-80,000 km ago (it's an educated guess). I admit however I had the choice between plantinum (cheaper) and iridum (more expensive). I went the el cheapo way.

After buying two OBD2 readers (one of which was more than 300 canadian rupees!) and after checking with the manufacturer to MAKE SURE it was compatible (it wasn't), I just gave up. That last one did, however, read the status of my hybrid battery.

In any case, thank you all for your imput, I will mention that to my mechanic when he calls me next (and I'm sure he's going to swap the spark plugs to test anyways).

I'll keep you posted so when the issue is resolved, someone else might find a fitting solution.

 

Finally got the car back. Thanks for all for your contributions. As usual, PriusChat is one fantastic place for all things Prius
The diagnostic was ... bad spark plugs!
Get yourself a virtual beer or coffee on me!