How important is that warm air hose on a '91 240

Post by **MadeInJapan** » 17 Jan 2009, 06:44

I hardly post questions in this section. The 240 we bought used ('91 240 sedan) last year when the weather was warm has no problems mechanically at all...and my son is driving it....but last night he told me that it has died on him a few times lately while he was going down the road...usually at an intersection when he came to a stop...but would crank right back up. I need to get out and check under the hood but it's been 10 degrees the day before and about 5 degrees yesterday. So, here's what I'm suspecting:
Noticed that the warm air hose that reaches around to the air filter housing is not there. It's just an open pipe...If this is the reason for the dieing issues, what do you replace it with? Just an open hose connection on the passenger side of the engine...I assume that the same spot on the air filter housing is blocked off, or is it? Guess I should take a look- but any suggestions here would be greatly appreciated.

Oh, and changed the thermostat a few months back... plenty of warm heat in the cabin but lately, my son says that the inside doesn't heat up like it did before (of course, it's extremely cold right now).

Kmaniac in California USA · Post by **Kmaniac in California USA** » 17 Jan 2009, 08:48

Something to consider here is the possibility of a vacuum leak on the vacuum source to the heater controls. A vacuum leak in itself could cause the stalling issues. Also, the heater control valve is vacuum operated and will not open or open fully without proper vacuum. Look here first before replacing engine parts on a wild goose chase. Chasing wild geese can be expensive and I have an empty wallet to prove it.

By the way, the warm air hose is there to help the engine warm up quicker after a cold start. Its an emission control device. A warm engine pollutes less than a cold engine and the quicker you warm it up, the less it pollutes. Once the engine is warm, it bypasses to cold air serves no further purpose. But if the bypass valve fails, too much hot air can cook an AMM. The lack of this hose shouldn't be an issue here.

Post by **MadeInJapan** » 18 Jan 2009, 17:30

Thanks, I'll check vacuum hoses. Glad to hear the large corrugated hose really makes no difference.