Butterfly assembly - removal and lubrication?

[cybercusp]

From what I have seen, it's always both springs are bad and you can tell they are bad just by looking at them. All the photos of bad springs show the same two or three coils that are spaced wider than the rest of the coils.

Both springs were bad in my case. Also it wasn't a "catastrophic" failure, but a slower one with the idle slowly creeping away from 750 over several thousand miles..like the springs were losing their tension with each use.

Was the butterfly valve assembly a supplied unit or was it assembled at the DMC factory?

[Jonathan]

Ok. Slight confusion here.

When I was originally mentioning lubing the "springs" I had intended on referencing the one on the throttle SPOOL (probably some of the confusion in the terms on my part) and the spring which is on the lever arm itself, but outside the throttle body.

I think we are all on the same page with what the throttle spool spring looks like, so no picture.

The throttle body spring in addition to the spool one, is the one in this photo shown on the right, connected to the lever arm:

Alex throttle body IMG_4325.jpg

(photos compliments of Alex's blog... thanks!)

It were these two springs I had assumed we were talking about in regards to lubing them, and more specifically, spraying white lithium grease and working it into the springs. This lever arm/throttle body one would be lubed in place, and the throttle spool spring would be disassembled, greased, and then put back together.

Now, the decel springs here:

Old Alex decel springs IMG_4178.jpg

New Alex decel springs new IMG_4311.jpg

I hadn't even realized these were in there. Are these cushioning the butterflies coming back to closed by coming in contact with whatever might be connected and touching at the back? As it looks in the photo, it isn't apparent what they spring against. I'm imagining it being similar to those little kitchen drawer decel springs you can buy from IKEA so the last inch of your drawers closing is slow and doesn't slam?

I've never opened up this portion of my car before. I don't imagine there would be much harm in at least taking it off and looking? It was mentioned not to remove the butterfly disc axle completely for not being able to get it back in centered, but to get the inspection or perhaps replace these springs, that might be easier?

[Bitsyncmaster]

The deceleration springs are for emissions and maybe help smoothing out the engine when dropping to idle. You don't lube those deceleration springs.

Your first photo shows the bad deceleration springs and the second shows good springs.

[David T]

The decel valves and springs are for preventing backfires on rapid closing of the throttle. Of little use on an automatic but necessary for the 5-speed. Most cars used a dashpot to allow the throttle to slowly return to idle. Not the fuel injected Delorean! I have no good explanation as to why those springs would go bad although one possibility is the car was adjusted and running so badly that it was backfiring a lot and the heat from the backfires eventually softened the springs. Just a theory.
David Teitelbaum

[Bitsyncmaster]

The decel valves and springs are for preventing backfires on rapid closing of the throttle. Of little use on an automatic but necessary for the 5-speed. Most cars used a dashpot to allow the throttle to slowly return to idle. Not the fuel injected Delorean! I have no good explanation as to why those springs would go bad although one possibility is the car was adjusted and running so badly that it was backfiring a lot and the heat from the backfires eventually softened the springs. Just a theory.
David Teitelbaum

My thought is....if it were heat, why do only a few coils look messed up?

[Dangermouse]

I've thought of that bad lot theory on a few other things within the car too. TABs come to mind. Although each time you start looking at it, you see quite the wide range of VINs for the people having the problems. The spring one here for example, has 3000, 5000, and 10,000 VINs which is a fairly wide range. Not necessarily that many months apart, but quite a few cars. We know Dunmurry didn't do everything super organized or "in order" (kind of like the matching numbers conversation), but you would have thought if they got a bad batch of something, and it was a box of 500 of that particular part, they would have used them on successive cars before opening up the next box of 500 parts. Hard to figure out what the guys were doing back in 1981... if only I had a time machine...

Surely the bad batch of springs would have been at the Douvrin engine factory, rather than at Dunmurry. You would perhaps expect an established engine facility to have better inventory control and testing but maybe not.