Throttle stuck open

[Bjorn Belter]

Had an interesting experience with my 340 Variomatic today. It doesn't get a lot of use to be honest, but it's MoT time. So I went down to the lock up, opened up and started the engine.

It usually starts after a couple of turns of the starter. It did today. I then pushed the choke most of the way back in, and gently touched the accelerator just to blip it a bit.

But then wow, straight up to max revs! I immediately turned the ignition off and all stopped. So I gingerly started the engine again and yep, straight up to max revs.

I think it must be the throttle cable as the pedal does "feel different".

Fortunately this all happened in neutral, naturally. But if it had "gone" when in drive or reverse, then, well, hopefully reactions would be good.

I had always thought that if a throttle cable failed, it would fail so that the engine could not rev. Seemingly not.

Any thoughts?

[Speedy88]

If it's been sitting I would put 20 beer tokens on it being a sticky throttle cable. Can you pull the throttle back up? If so then I'd get a new one (or if you're cheap try lubricating it with hot soapy water)

[Ride_on]

It could be frayed, in which case the broken ends are jamming up the cable and lubrication is not going to help. It could also be a broken return spring at carb.

Inspect it first before buying anything.

[Chris_C]

Agreed. Every stuck throttle I've had on 1.4 and 1.7's has been the pivot pin on the pedal jamming up and needing grease, there are a few things that can cause the symptoms.

It's an easy job though... so could be worse!

[Bjorn Belter]

Thanks for the comments.

I had a bit of time today to have a closer look.

It appears to be the spring arrangement on the bulkhead. It is no longer "compressed" and the thing that goes on the end of the cable doesn't seem to be firm. I estalished this because pushing it in by hand slowed the engine down.

Any idea what I need to tell the garage to get in terms of bits etc? They are going to tow it away next week sometime. (Hopeless I know but if I try to fix anything, I usually make things worse)

[macplaxton]

(Cut 'n' shut from DOC post)

I think you're playing with the wrong end of the cable there Mr B. Whip the air filter housing off and look at the carburettor end too.



(Pages linked from my Flickr and from the Green Books, click image for larger versions)

The springy bit you describe is the kickdown switch, as outlined here:



By you pressing it, you are just shortening the outer cable. Have a proper look at the inner cable at both ends. Even my brother could manage to do this even though he's a grade A technical numpty.

So it's a choice of:
a) inner cable not sliding smoothly in the outer
b) pedal pivot stiff/seized
c) return spring at carb end
d) carb linkage stiff/seized

Have another look and determine which it is.

HTH,
Rich

[volvosneverdie]

Good work Rich.

I vote a mod best sticky this, as its bound to be an issue recurrent.

And I can never find threads when I need them.

[Chris_C]

MP, how much of that post is yours and how much is the DOC? If it's yours and you are happy, I'll cut your post into the "readers fixes" part of the technical section, I just don't want to tread on toes if you arn't the orig author

[macplaxton]

It's all my post on the DOC forum. The pictures have been borrowed from the V3M green books pdfs.

It's a cut 'n' shut because I know not a lot of people look in there and thought it worthy of duplication.

[Bjorn Belter]

I went down to have a look at the car again today and took my camera phone with me, and this is what I think the problem is: http://www.youtube.com/watch?v=0nLdv7DDa5U

I think the problem is definitely at the bulkhead end of the cable.

Oh yes, this is what it looks like when it's out and running properly. http://www.youtube.com/watch?v=xGMGAhZds1U

Hope to get it recovered to a garage in the next few weeks and sorted. Poor thing is gathering dust at the mo.

[volvosneverdie]

I went down to have a look at the car again today and took my camera phone with me, and this is what I think the problem is: http://www.youtube.com/watch?v=0nLdv7DDa5U

I think the problem is definitely at the bulkhead end of the cable.

Oh yes, this is what it looks like when it's out and running properly. http://www.youtube.com/watch?v=xGMGAhZds1U

Hope to get it recovered to a garage in the next few weeks and sorted. Poor thing is gathering dust at the mo.

I love this car.

[pettaw]

That spring you're playing with in the youtube video is irrelevent to your fault. You need to take off the air filter and disconnect the throttle cable from the mechanism beside the carb. Then play with it and if its sticky you'll need to take it off the car and lubricate it up properly so it starts working again. There's also an outside chance it could be the carb butterfly getting stuck too, but 90% sure it's the throttle linkage.

BTW don't pay a garage to fix this much easier and more satisfying fixing these types of things yourself, particularly if its a CVT, garages don't have much clue altogether about CVTs. Every CVT I've encountered has had a knackered clutch, no matter how few miles on the clock. We think its because they rev them up in park.

[Bjorn Belter]

Thanks Pettaw. Unfortunately, I have a strange effect on things when I try and repair them - I usually make them worse.
Or, when I take something apart, i can never get it back together again without having a few bits left over.

Anyway, i had the car recovered to an independent Volvo specialist, who were the same people who put new clutch and drive belts on it a couple of years ago. Unlike most garages, this one does understand and actually likes/appreciate the Variomatic.
I had rescued the car from being abandoned at a PX auction - one owner etc. The clutch had well and truly had it when I got it so I got a brand new one from Holland and it drives as good as new. Just as DAFs/Variomatic Volvos should.

They eventually made a new cable. I got the car back a couple of weeks ago, and it seems OK so far.

Poor thing is now back in the lock-up getting cold. I think I maybe being cruel to it to keep it, to be honest. I rarely get a chance to use it.

[foggyjames]

I dunno Richard...I don't think it's that cruel! Most 300s die due to rust, and the cars I have which are the least rusty have spent much of their lives garaged...so even if it's not used that often, at least it lives to fight another day!

cheers

James