Major rattle at idle...adjust idle screw?

[ventureforth]

I just got my '82 1.6NA Rabbit back from the body shop.  They straightened the frame a wee bit and fenders due a fender bender from the PO.  Now it rattles like I've got a 4BT under the hood or something.  It ran smooth as silk before, so I'm not sure what they could have done.  The thing is, if I give even the slightest bit of throttle it gets smooth again.  So, is it just a question of adjusting idle (I know, why don't I just try and I'll find out)?  My only question is how anything they would have done would have any effect on idle speed.  All they did was replace core support (I now have an awesome Westy front end) and the fenders and fixed the hood... and straighten the frame a little bit.  They wouldn't have had to touch the engine at all.  At speed it runs super smooth, but whenever I depress the clutch or idle when stopped, it's like I'm sitting in a Sharper Image massage chair.  The only other weird thing is that sometimes...only sometimes...as I'm coming to a stop, the engine rattles, then stops rattling for a moment, then finally rattles again full force.  Could it be something with the clutch or transmission?

Any thoughts would be much appreciated.  I'm gonna try the idle adjust first unless you all have other ideas.

Thanks.

[TITan]

Since they did not touch the engine I'm going to say it's the engine mounts. Now that they straightened everything out the play in the mounts makes it rattle like crazy.

[ventureforth]

So do you think the mounts were crapped out before they fixed the frame and were just being forced in to good service by the extra tension on them from the bent frame...or the process of straightening the frame damaged or warped them?  I ask because I'm trying to figure out if I can make a valid argument that it was caused by the body shop, or if I have to suck it up and take care of it on my own (it looks like a pretty easy job and the mount kit is only $50 from partsplaceinc, so I'm sure I can do the job myself if I have to)?  It's mostly an issue of time, or lack thereof.

Thanks.

[Vincent Waldon]

Might just be that the engine/tranny is just a bit out of alignment now.

I'd be inclined to loosen all the motor mounts, align the engine/tranny as per spec in the manual (or at least wiggle it a bit to "centre" it) and then tighten everything back up... and see if the issue persists.

[Turftech]

Could it be something with the clutch or transmission?

Not like this is what's wrong, but just as an example...  I had another front wheel drive (Honda) a few million years ago that was in a "minor" fender bender.  <5 mph "bump" into a car in front.  (At least the wife swore it was <5 mph)  Pushed the bumper shocks in, and actually needed to have the left front pulled out a hair on a stretcher, but otherwise little damage.  However, from that point on, the damn thing was hard to start and stalled when dropped to a sudden idle from speed.  The valves sounded much noisier as well.  About a month or so later, the engine just stopped turning while cruising along at 65 mph!  Wham!  Just stopped.  Turned out the crankshaft had broken in two right at a journal.  My boss at the time figured it got cracked when it had the front ender.  Made sense.

Like I said, You probably don't have a cracked crank, but who knows what happened when all that steel suddenly came to a stop.  Could be anything really.  I'd get deep into her for a while, just to make sure there aren't any surprises.  I agree about the mounts too.  Just looking at them in a bad mood can cause cracks. 

Happy hunting!

[ventureforth]

UPDATE

So, I replaced the upper tranny mount (the one near the battery) and the rattle is absolutely and completely gone.  It's even better than before the rattle began.  The whole thing is super quiet...almost too quiet.  That might be because I had added DynaMat in the meantime.  The steering column rattled a bit at first, but only when coming to a stop.  I adjusted the freeplay in the clutch, idle speed, and max fuel to what I believe is correct all around, and now the steering column rattle is gone, too.  I have no tach, but the idle sounds pretty relaxed, so I'm thinking it's okay.  I basically increased idle speed until the idle was right at the point where the motor smoothed out, then turned it ever so slightly higher.  Adjusted max fuel so that it smoked black and then turned it back a quarter turn.  Adjusted freeplay in clutch per Bentley.  I have some new (well, remanufactured) injectors to install this weekend.  I'm hoping it gets rid of the smoke (as I smoke at all max fuel levels and all gears and speeds except cruising in 5th on the freeway...and I'm sure I smoke a bit then, too, but it's light enough to be invisible to me).  I also have mounts for the other mounting points, but will replace those when I replace the pump and timing belt.

Did I do anything the wrong way?  Should I have calibrated idle and max fuel differently?