So my 240 has been running like a champ (other than the catalytic converter heat shield rattle) for quite some months now. However, over the past 2 days I have was hearing something funny. So when I rev the car up using the throttle body itself, there is a whine/growl that is present when the engine is going back to idle RPM. It sounds just fine while revving up - the sound is present only while going back to idle.

The intensity of the sound increases the more I rev (the higher the difference between "revved" RPM and idle RPM - the more prominent the sound). Also it is more audible on the intake side of the engine.

Any ideas what is happening? Thanks!

 

Forgot to add, I checked this after driving about 25 miles on the freeway and its 45 F here.

 

is your engine oil OK ?

what about the belts for the AC compressor and power steering and alternator ? is one of those what is making this sound?

maybe your flame trap is flugged up, and revving it is blowing it out ? what kind of shape is the oil seperator box and its vent hoses in ? (this is under the intake manifold on the slide of the engine block)

does this 1991 have an EGR valve? (generally on California cars). that could be sticking open or something.

what kind of shape are your engine mounts in? is the engine shifting too much when you rev it like this, and knocking air plumbing loose, so you're hearing intake noise?


hard to guess anything else without being there, seeing/hearing it.

 

The oil is fine (changed about 1300 miles ago and has 10W30 in it right now). I had changed the flame trap a couple of months ago. Its got no EGR as the cars been in Ohio all its life. The engine mounts seem fine - the engine does rock a bit during acceleration but nothing crazy. Idle is very smooth with barely any vibrations at all. The belts also seem fine - I had changed them as well as the timing belt with new tensioner about 10K miles ago.

But the temperature has gone below freezing. Could that 10W30 oil be causing issues? Should I switch to 5W30 ASAP for the colder temperature or can I wait till I get to 3K miles?

 

i never change my oil any more often than 6000 miles, its just wasteful.

Volvo 1991 240 Model

says 10w30 is good from -4F to 104F. if you put 5w30 in there, you shouldn't drive it over 68F. if its -20F, you probably shouldn't be driving anyways

 

haha. I wont drive in -20F! I usually drive my '96 Maxima once winter sets in completely so that the 240 wont turn into a rust bucket.

Anyways, the whine was coming due to one of the vacuum hoses having come off. I replaced the hose itself and everything seems fine now.