Hello everyone, my 94 Accord DX Automatic trans, 150,000 mi is really acting up, lots of weird symptoms, LOTS of engine vibration.

It started when I was backing out of a parking lot, the whole car was shaking really badly when I shifted into reverse, and when I shifted into D and drove away I didn't notice any more vibration. Later on, I noticed the vibration had gotten worse, and now occurs in D and R gears, the car does not need to be moving to start all of this ridiculous vibration, simply have it on, and when its warming up, warmed up, or idling, or in reverse, it vibrates like crazy.

The moment I put my foot on the accelerator, in D gear, the vibration seems to cease, at first, the car becomes smooth as it has always been, in drive though, when going 20mph or so, the engine begins its vibration at certain rpm areas, like 2200rpm for example, then disappears at a higher rpm, it feels very rough everywhere I drive it.

I've heard its the rear motor mount, yep, the one with the vacuum solenoid, so I replaced it myself, it took a LONG time, removing the intake manifold took forever, about 8 hours including me annotating where every bolt went, vacuum lines, etc, very tight spaces when you're under the car and removing the intake manifold. I removed the old mount, which seems to hold its vacuum when i move the arm you can hear a woosh from the vacuum diaphragm, so I figured part of it works, whatever the internal workings of this mount are I've no idea how to check if its good or not, either way, old rubber part, I figured it would be working with a new rear mount. 5 Hours re installation.

After changing the rear mount, it feels EXACTLY like it did before. Still plenty of vibration, the feeling that my car is going to die and strand me wherever I might drive.

I also changed the front engine mount while I was at it, the front one was completely worn out, the rubber had cracked and detached from the bracket. So far, new front engine mount, rear engine mount, intake manifold gaskets (lower and upper), front engine mount took 2 hours to change if anyones wondering.

I've seen plenty of threads with no solutions in them with this same topic, does anyone actually know a fix for this sort of problem? I've seen threads where people were changing the vacuum solenoid too, the one that hooks to the intake manifold and the rear motor mount, thats next on my list, but according to what some people have said on forums and such the problem is still there after that part had been replaced too.

I figured it would be a vacuum problem, because as soon as I accelerate forward the vibration goes away, comes back later as rough brief bits of vibration when I'm on the throttle (certain rpm areas), very violent vibrations when I let off the throttle, (high vacuum), I even engine braked into 2nd gear when I was going downhill, maybe 30mph, car felt like it would rattle itself to pieces!

What else is there to do? Was the new rear mount bad?

More importantly to me, will I be able to drive my car in the meantime? Will driving it in these circumstances make the problem worse or have the potential to leave me stranded?

Anyways, I appreciate any input, this isn't the first case of this happening, and its not just me that needs help with this problem, but I have yet to see a solid solution, diagnosis, I'd rather not take to it a stealership and pay 10x more than needed, but I'm feeling like I've got no other choice.

Thanks for your time, I could really use some the help right now.

-Michael

 

I hate to ask but what about the other mounts?

Misfiring can also cause vibration.

 

Thanks for the reply,

It looks like the other mounts are intact, theres the one on the passengers side of the vehicle thats bolted to the transmission, the other mount on the drivers side is difficult to see into if its broken or not, I really cant tell 100%. The top part of it is leaning against the power steering pressure line I believe, maybe a return line, but I cant remember if its always been like that, I can put a jack under my transmission and jack up the whole car without seeing lots of play in the mounts, or any play in the mounts for that matter.

The thing is, the motor still has plenty of power, doesn't vibrate when I'm on the throttle, its only at idle or part idle when its rattling like crazy, when I initially accelerate it feels smooth, but holy crap, whenever I'm off the throttle it feels awful! So I'm not so sure its a misfire kind of situation, misfires would feel different too, and since the motor responds great to the throttle I dont think its a misfire problem. I'm not ruling it out just yet, but its one of the lesser likely causes I'm thinking in this case.

I appreciate the input!

-Michael

 

What is your idle speed? Low idle speed can cause vibration. Fix is cleaning throttle plate and idle air control valve. See DIY forum for "idle problem".

good luck

 

Thank you for the information,
My idle speed is around 700rpm, which, when the engine was running correctly, 700rpm idle was very smooth, no complaints there, but whatever happened recently thats causing all this vibration is ridiculous, if the IACV was broken would the engine still shake badly during engine braking while driving, as well as when its idling-warming up/warmed up?

When I took the intake manifold off I noticed a little carbon buildup in the intake runners, I discovered some oil in them also and replaced the PCV valve while I was at it, the throttle body seemed pretty clean actually, maybe a little carbon, but nothing like a massive amount caked in there or plugging up a passage way, I'll take a look at that thread you mentioned though and see if anything will help. I'd rather not work on the intake manifold again if I can help it, I could remove the throttle body from the intake runners and clean the IACV though if needed I suppose.

Your help is very much appreciated!

-Michael

 

There is a prescribed procedure for aligning and tightening the motor mounts. I've heard that not following the procedure can result in problems.

If you don't have a shop manual download a manual from the Online Manuals post in DIY forum. Look in Engine Removal/Installation section under installation for procedure.

I have a similar but different problem w/ my 94EX. It has a vibration under acceleration, but idles OK (small vibration). I too have replaced front and rear motor mounts.

BTW, your procedure for rear mount installation is the heard way. It's a tough job, but easier to work from underneath to remove the rear.

BTW, carbon in the intake manifold is normal. All have it. It's a consequence of PCV oil baking on the passages. Some oil in all PC flow.

good luck

 

When the intake was off, did you clean the EGR ports. Prob not an issue but something to think about.

When was the last time you gave is a tune up (cap, rotor, inspect wires, plugs, ect)?

 

Hello, and thank you for your input, sorry to hear about your vibration problem as well,

I found a thread that had a pdf of a Honda service bulliten for the vibration issue, it included procedures for removal and installation of the rear motor mount, the three bolts that attach the rear motor mount to the chassis take 43 lb ft of torque and the long bolt that attaches the bracket to the mount takes 47 lb ft of torque, the bulliten just says reinstall all removed parts after that. The only way I managed to reinstall everything by myself was attaching the mount first, torque the 3 bolts to spec, install the bracket that attaches the motor to the mount, torque specs were not given for those, I installed the bottom bolt first, then top, then middle, snugged them up, torqued the bottom first, then middle, then top, tightened as best I could past snug. After the bracket was reinstalled I could bolt the mount to the bracket, this took a long time to figure out, as I didnt have another pair of hands, I installed the bolt halfway, from passengers to drivers side, the other side of the mount will not line up with that bolt unless you force it to, I had to take a screwdriver, jam the handle of it into the mount as to contact the inner part of the mount where the bolt exits the mount and enters the bracket, then I used a hammer, the prying end, as a lever that pushed the mount down enough to get the bolt through, torqued that up after it was in there. Its the best I could do with conventional tools, a c clamp would have worked better I bet but it would have to be huge , and getting it in there would be difficult as there is little room as it is.

Yeah, Hondas procedure was to remove the center beam, the intake tube, a driveshaft (drivers side I believe), oil filter, to get to that bracket as well as the mount. Ill see about posting that bulliten in a moment. Either way its a pain, my biggest thing was having room to work with, even with a universal joint on a ratched with lots of extensions etc it woukd be very difficult to install the new mount, removing the intake allows the room necessary, though it is a pain too, I had to remove the gasket from the head and the intake manifold (got stuck in places) to both, screwdriver wasnt scraping it off well so I used a dremel and a wirebrush to remove stuck material, plus I wasnt aware that coolant runs through part of the intake manifold, found that out quick as it spilled out onto my garage floor lol, I had to remove alot to get that intake manifold off and back on.

Is your vibration at certain rpms, or just the entire time you have your foot on the throttle?

Thanks again!
-Michael

 

Hello,

I looked at the EGR ports, they seemed okay, I suppose I should have taken off the EGR valve from the intake as well, but the ports didn't really seem clogged up or anything, just the usual carbon buildup as expected.

I changed my spark plugs about 5K miles ago, NGK IX Iridiums, gapped to .044 I believe. I think the ignition wires are stock to my understanding, they say Mishimoto on them if thats any clue, they are not cracked or frayed. I should pull off the ignition cap and inspect the rotor while I'm at it, but as I've mentioned the car has plenty of power, doesn't feel like a misfire, doesn't sound like a misfire, so I'm thinking its less of an ignition issue, possibly the motor mounts or maybe something thats severely off balance... but the way the car responds to the throttle is just weird, because the vibration stops and the car becomes smooth once I accelerate forward, only when I'm off the throttle does the car become nasty and feel like its going to die from all the vibration.

I appreciate your thoughts on the matter,
-Michael

 

Your procedure for the rear mount is wrong and may be contributing to your problem. You should have installed all bolts connecting bracket to engine loosely, then install mount-bracket long bolt loosely, then tighten bracket-engine bolts, then mount-bracket long bolt.

That's what Honda shop manual says. Reason for this is to allow mount to be unloaded in the engine off -static condition.

Note, I'm not saying your procedure is the reason for vibration, but it could be.

Yes, the vibration occurs generally about 2000-2220 rpm under firm acceleration. Seems to be felt more in steering than through gas pedal, which made me suspect CV axle (relatively new AZ axles). I need someway to definitively establish if mounts are causing vibration or something else. I haven't come up w/ a fool-proof way yet and hate the thought of replacing the mount to find it's fine (which I suspect is the case).

good luck