My 89 240 automatic (88k miles)has had various symptoms lately and only today I discovered (didn't pop the hood until today) that my heated air intake hose is completely broken...the metal is totally sheared. Can anyone confirm or deny that this broken hose would be the cause of any of the following symptoms:

1. I'm guessing the hose would explain the rough idle, the louder-than-before exhaust-type noise and the near-stalling/stalling upon startup?
2. Check Engine light at startup?
3. Overdrive going off all by itself (orange arrow has come on twice now on its own?)

Do all of these symptoms sound as if they could be, directly or indirectly, the result of the broken intake hose and what else should I be concerned about if this hose has been completely broken for...oh, let's just say a couple of weeks for fun. Mostly around town driving with a little highway for good measure.

Gratefully,

Chesapeake Tom


p.s.-I've been lurking around this site since I got the Volvo last fall and I am, to put it plainly, dazzled by you folks...I credit this board for pretty much everything I know about my car. Admittedly this doesn't amount to an awful lot, but it's miles beyond what I ever expected I would learn about cars or engines...The vast majority of the greybeard wisemen on this site tend to write very well and it just keeps me coming back...learning about a new subject should always be this fun...

Thanks again.

Remove the pre-heat hose cmpletely and buy a 2.5" diameter rubber plumbing end cap with band clamp. This will slip over the inlet on the airbox and cap off any hot engine bay air from reaching your AMM. Hot air feed to the AMM from a failed airbox thermostat is what usually kills the AMM. You would not know the airbox t-stat had failed until is already did its damage to the AMM.

Warm air at start up has to do with emmissions and is not a big factor in engine performance while cold.

If you live in a state that requires emissions inspection, you shouldn't remove the hose. Here in Noo Joisey, they (sometimes) look under the hood to check for "tampering". You'll get dinged for a missing preheat hose. Of course, they don't look inside the airbox, and will never notice if the thermostat is gone and the hole is plugged. They just want to see the hose in it's original location.

That hose would not cause any of the symptoms you list. In fact many people including myself eliminate the heated air going to the intake by disconnecting the hose. There is a thermostat in that box that can fail and direct heated air into the intake at all times (rather than shutting it off or blending it with cooler air). I wouldn't repair the hose on a bet.

1. The near stalling might be simply a throttle body that needs cleaned. Rough idle could be a variety of things. Louder exhaust sound (?) perhaps a bad exhaust manifold gasket.

2 Is it a "Check Engine" light or a "Service" light. The service light comes on as a reminder every few thousand miles to remind you to change your oil. It can be reset by finding the reset tab on the back of the speedometer.

3. Overdrive with a mind of its own is probably a bad solder joint in the relay. The relay is accessed by removing the glovebox and reaching to the left side of the opening. Take off the cover and resolder the connections on the printed circuit board. Or if you prefer you could buy a new one.

Randy

The preheater air hose makes the car run better when it is very cold out by preheating the air. I dont believe it would cause your problems or the check engine light. You need to retrieve the fault codes by following the directions either in the posts or by using a bentlys manual... The overdrive light going on and off would probably be the overdrive relay. Smack the shelf area by the center vents and see if you duplicate that problem. If you do then resolder the od relay which is simple and effective. Good luck Dave.