Throttle stuck on highway

[454cid]

I'm probably wrong, but that thermostat in the airbox used to be replaceable. Then I think the thermostat went NLA, but I believe someone figured out one from a 240 would work?

When I looked at this before, I think there was a design change at some point. Nothing seems to come apart at the air flap mechanism on mine, and it's vacuum actuated. The thermal switching takes place higher on the box. It looks like a simple temperature activated shut off for the vacuum. I haven't bothered to try testing that, as it's irrelevant if the flap won't move correctly.

I should add that it may be worth trying spraying the throttle cable return spring with WD-40. They can get sticky and in cold weather it will amplify the issue.

Good idea. I will do that.

[erikv11]

For my car it only happened on very cold winter days like 5-20 ˚F, so not humidity related. On mine the flap also wouldn't move but I would force it to cold most of the year, but to warm (fed by preheat hose) in the coldest winter months.

My take is that if you jam something in the airbox flap so it's stuck to warm the car will be good. When it warms up you can clean the throttle plate. Lubing throttle parts for good measure etc are all good ideas from MVSers.

[454cid]

For my car it only happened on very cold winter days like 5-20 ˚F, so not humidity related.

Ok, so not so much cold plus excess moisture, but just plain extra cold conditions. It was probably right around 20F at the time it happened. Maybe I was pulling in extra moisture from snow accumulated on the front of the car, too.

I'm a little mystified why Volvo needed to have a system like this, to avoid the issue. Other vehicles I own, or have owned, don't have a system like this, and don't seem to have throttle plate freezing issues.

On mine the flap also wouldn't move but I would force it to cold most of the year, but to warm (fed by preheat hose) in the coldest winter months.

My take is that if you jam something in the airbox flap so it's stuck to warm the car will be good. When it warms up you can clean the throttle plate. Lubing throttle parts for good measure etc are all good ideas from MVSers.

I don't have to do anything to make it pull warm air. It's held that way by the spring inside. That was the original issue that I solved by just eliminating the flap with the lower box from a turbo.

I just came inside from spraying the spring, and linkage. I found I don't have WD40 anymore, so I used Blaster's Corrosion Stop on the spring which is a lanolin based product, and Liquid Wrench on the linkage. Not that it felt bad before, but it's really smooth acting now.

[rolsen11]

When I looked at this before, I think there was a design change at some point. Nothing seems to come apart at the air flap mechanism on mine, and it's vacuum actuated. The thermal switching takes place higher on the box. It looks like a simple temperature activated shut off for the vacuum. I haven't bothered to try testing that, as it's irrelevant if the flap won't move correctly.

I believe you are correct, if it's the same as what's in my 2000 V70 it should look like this, correct?

I haven't figured out how to get mine to work correctly either

[454cid]

When I looked at this before, I think there was a design change at some point. Nothing seems to come apart at the air flap mechanism on mine, and it's vacuum actuated. The thermal switching takes place higher on the box. It looks like a simple temperature activated shut off for the vacuum. I haven't bothered to try testing that, as it's irrelevant if the flap won't move correctly.

I believe you are correct, if it's the same as what's in my 2000 V70 it should look like this, correct?

20240915_165321.jpg
20240915_165331.jpg20240915_165413.jpg

I haven't figured out how to get mine to work correctly either

If I recall correctly that part on mine is metal, but probably works the same. I had the engine running when I changed the box, and the filter stuck to the lid, so I didn't see that area, this time. The outside looks very similar with the two ports, and the metal clip sort of bent around them.

[abscate]

That gizmo in the air cleaner is the temperature regulator. And shunts vacuum to the air door down at the snout to choose either ambient or exhaust heated air. Turbos don’t have this as the air is warmed by the turbo or cooled by the inter cooler as needed, open loop. My T5 was iced up slow running in cold wet traffic in Providence, giving ETS errors. Once I got on highway with nominal boost, it thawed out

[scot850]

Due to freezing intercoolers up here, if it stays continuously low temps, then I and others have run a piece of cardboard behind the grill held in place by zipties. Only safe to about +5-10C. You could do this too for a non-turbo to reduce how much cold air enters the upper part of the engine bay. For winters, this is where an engine undertray would be great on a P80. We didn't get them for some reason.

In Sweden they got a plastic try that fitted over the grille to prevent freezing issues. I have been looking out for one of those but no luck. However, the garage Princess is only run in the summer/fall now so not an issue. P2's have an undertray which helps.

Neil.

[yanga001]

Had this happen on a cold day with my brother quite a few years back. It was stuck near full throttle for a few km before we put it into neutral. That reset the throttle for one reason or another.
Never did it again since.

However I did have a s70 with a bound throttle linkage due to buildup of rust proof at, oil, and debris. Was extremely bound up, however a full disassembly and greasing it completely restored functionality.


Things can shrink in the cold, so if it’s purely temperature I might suspect debris buildup. As others said, clean and grease for good measure.