Engine Torque Mount Confusion

[Benjamin4456]

Alright, I don't know what it is with these cars and their weird engine mount variations but they keep throwing me for loops. I'm just trying to fix these darn idle vibrations gosh dang it...

I was just about to swap in a new torque mount (the dog bone tie on top of the engine) and noticed that my new one is different from the one I just pulled out. Not only is the width of the larger hoop slightly different, but so is the diameter, and even the length of the arm. It doesn't look like the one I pulled out is original either, which is unfortunate since I don't have a ground zero to compare to. Additionally, the larger bushing from the one that was in the car says 5MT on it, and this is an auto car, so what gives? Are there differences or something?

The new smaller bushing seems to be identical, so no concerns there. The new larger bushing seems to be identical to the one I pulled out as well (minus the 5MT lettering), however it came pre-installed in a much different shaped hoop than the original. The original also appears significantly squished like it wasn't suppose to fit in the smaller hoop. The larger bushing also doesn't fill the full width of the new arm, which almost makes it seem like the old arm is correct, except for how terrible squished the old bushing is.

So anyway, if you're still somehow with me and aren't already confused enough, here's a handful of photos.











Any thoughts here would be greatly appreciated. I genuinely do not understand why the mounts for these things seem so off in the aftermarket.

[ShiRen]

Well the dogbone isn't gonna do much for idle vibrations, it's for the engine rocking when you shift or let off the throttle.

Everything is off because the car is old and the parts aren't as well documented as some are now. If a manufacturer has something that vaguely matches the right specs, they might try to sell it. Sometimes the vendors own parts get superceded and the new part is actually incompatible, but the car doesn't get dropped from the compatibility list

[Benjamin4456]

Thanks for the reply ShiRen. I should have specified that the vibrations are specifically at idle when in gear (aka when the torque mount is actually doing something). In Park or Neutral the vibrations are not an issue. RPM is stable as well, so that's not it either. They can also change slightly depending on the incline of the road surface; another reason the torque mount seemed likely. Plus the old mount rattled.

I've worked on plenty of old cars that have not had weird part inconsistencies for major components like this, although I've never worked on old Hondas before. Just seems surprising. Also still find it weird how Honda used different engine mounts depending on the trim (at least in the front) but only one of them is still available. Granted having various engine mounts isn't uncommon, it's just the fact that one of them straight up does not exist anymore that's weird.


I think I'm going to try the new mount as it came, especially since it seems more pliable as configured than the old one which seems like a good thing for NVH. Hopefully it's not too long though, that's my real concern. Since the front mount is too tall the engine already leans backwards some and the slotted mount for the torque arm was already pretty far to one side.

Either way, if someone happens to have an original Honda torque mount laying around I'd be really curious what the dimensions of the larger hoop are. That is I.D. and width mainly.

[ShiRen]

This is an automatic I assume? The dogbone is still not doing anything in that situation.

You say that the rpms are stable, well they probably are because it's under load. However, when the rpms drop from putting it in gear it's gonna vibrate, my car does it with the AC (it's a manual, however it has no idle control). This is an idle control issue, it's supposed to raise under load, it will be a lot smoother

[Benjamin4456]

It is an auto, and yes the dogbone is doing something in that situation?

When you put it in gear the engine is torquing itself when stopped because there is now a load applied by the CV axles trying to twist. If it wasn't torqued then there would be no motion from the vehicle when you let off the brake. Am I missing something here? The engine quite literally rocks slightly forward or back once in reverse or drive. The torque brace/mount is what limits this rocking. If you're in gear and idling along at a constant speed then sure, the dogbone is doing nothing, but not when you're at a complete stop.

Idle control is just dandy. It stays locked at 750 rpm like the manual says regardless of load; headlights, AC, power steering, putting it in gear, etc. Sure it drops briefly when something engages since it can't react instantly, but it's not dropping excessively low and it recovers quickly. Based on what I understand from the manual, the engine is supposed to stay at 750 rpm, not raise when load is applied. It needs more air to maintain 750 rpm with extra load, however the rpm itself does not rise. Perhaps it's different for the models without an idle valve?

This particular 87 LXi is equipped with the remote mounted IACV (or whatever Honda calls it), and it seems to be doing the job correctly. If I use the idle air screw to raise the idle manually, the IACV adjusts against me and brings it back down to 750 rpm. That's where it wants to be apparently, and to my understanding is where it is suppose to be. I was able to get the 87 service manual as well, so this shouldn't be an oversight based on the more commonly published 89 manual.


Anywhosit, I replaced the dogbone with the new one and the idle vibrations when in gear at a stop (to clarify) have improved a good bit. The rattle I was noticing is also gone. Because of the incorrect taller front engine mount leaning the engine slightly backwards and to the right, it is unfortunately slid all the way to the one end of the slotted bolt hole, but I don't think there's much to do about that (other than find the right front engine mount).


Still curious about the differences between the various dogbones and why I have two that simply don't match. Open to ideas.