my friend's sc400 seems to do something a little scary.

he was hoping someone on CL could help diagnose this problem.

when he's driving, sometimes the car just dies on him. one time it was as he got off the freeway, going about 10 mph on the offramp.

another time, cruising at 30mph.

and another time, stopped at a light.

his rpms seem to drop when he turns off the AC, and or radio. this is most noticeable parked. the rpm gets down to about what looks like 500rpm.

to get the car started again, he just stops - puts it in park, and it cranks right back up w/ no hesitation.

also, when accelerating from stop, there is a lull and a small thump noise when he steps on the gas.

it seems like the car accelerates a bit slow as well.

i am wondering, if this is early signs of his alternator going bad. any ideas?

someone else proposed that it was the throttle body, but that seemed like a strange diagnosis to me....

thanks

 

moved engine question to engine forum.

 

For that issue, these 2 below maybe the culprit:

1. losing air pressure in the intake
2. Idle Air Control problem.

I had the problem before and mine was the IAC.
The transmission's mount has gone bad or the driveshaft bushing.
I would think the throttle body is dirty. Here is how to clean it. While you are at it, you could also replace the spark plugs as well. Don't forget to reset your ECU once you're done.

Hope that helps.

- Dom -