Hey everyone,

So I am completely new to this forum, and to any car forum for that matter. Two days ago I had put a post in the "New Member Introduction" thread, but for some reason it's not showing up at all. It says under my profile that I have made one post (prior to making this one) which was in that thread but for whatever reason I cannot see it. Just wanted to get that out of the way for some context for me being here.
Anyways, I am looking for any kind of help or advice I could get for a problem that I am having with my car. Back in February of this year, I picked up my first car off of Craigslist. It's a 1990 Honda Civic DX Hatchback with a 1.5 L engine and 4-speed automatic transmission with about 133,000 miles. During the first test drove that I took, I backed it out of the guy's driveway and noticed a rough shaking sensation. It made a droning noise on the inside and the only thing I could visibly see shaking was the steering wheel (This was happening in reverse with my foot on the brake to control my speed out of the driveway). The guy I bought it from had told me it was doing that because of a bad motor mount, and he was able to replace all but one of the four, which was the rear motor mount. He gave me the replacement rear motor mount, and with the help of some friends we got it replaced (Huge pain in the ***, but got it done). That didn't seem to make the shaking go away. After popping the hood and having people watch the engine while I went through the shift pattern, they noticed that there was a lot of movement in the front of the engine and determined it to be the front motor mount that needed replacing. We eventually replaced the front as well, but once again that did not stop the shaking. Just to keep in mind, both of these motor mounts were torqued into place, not following any sort of torque specs (I didn't think that would matter with engine mounts as long as they were tight). To this day, the shaking always happens whenever I am in Drive and stopped at a red light for instance. Because of this, I usually put it into Neutral to ease the shaking, which helps a lot but does not make it disappear entirely. I sometimes just put it into Park, which has the same effects of putting it into Neutral. The same shaking happens when I am backing out of the driveway with my foot on the gas pedal to control the speed I am reversing in. However, as soon as I am driving without any stops, the engine runs smooth as can be. During this past summer, I would also notice that turning on the air conditioner (which works perfect) would cause a small spike in the shaking. I want to apologize for misusing any terms as I am really new to car repair and maintenance but I'm eager to learn more. Thank you so much for your time reading this and if I could get any sort of advice or help on how to deal with this I would greatly appreciate it.

 

You may need to clean the idle air control valve (IACV), sometimes called the electric air control valve (EACV). This valve regulates the amount of air bypassing the throttle plate when the engine is under various loads. Since your car is an automatic, holding the brake at a stop while the car is in gear puts the engine under load. Turning on the AC puts the engine under load as it now has to work to turn the compressor. You can search the forums or Google for how to clean the IACV. See if that helps.

 

do you know if these were stock replacement mounts? or aftermarket 'race' mounts.. if you are using aftermarket mounts they may have a much higher stiffness than the stock mounts which transfers the normal vibration of the motor to the body much more harshly and is usually more noticeable when at a stop

 

They are stock engine mounts. I know of the aftermarket/race ones that you're talking about though. Do you think the torque specs of them have to do with anything? I definitely know that they are not loose but I didn't know of any torque specifications.

 

I will definitely take a look at it. Ever since the the guy that I bought it from put it in my head that it was a motor mount issue I guess I sort of got tunnel vision. I will give it a shot and let you know how it turned out.

 

I'm sure the have a torque spec, but with mounts I just go as tight as i can by hand, then (when accessible) use a big breaker bar to get a little more tightness and move on

 

It definitely sounds like bad mounts but cleaning the idle air control valve could help. Does the motor make any put put sounds like it is misfiring at idle?

 

No, it never sounds like it's misfiring at idle, just a rough shaking sensation. If anything, it does something similar to that when I first start it up and begin driving in the first couple of seconds, but that usually only happens when it's cold outside and goes away pretty fast. I'm guessing that just has to do with the fuel injection system which I understand was fairly new technology in this generation Civic.

 

It looks like you're not alone:
https://honda-tech.com/forums/honda-...2801796/page2/

On there they mention a couple interesting things -

1.) Aftermarket mounts could have harder rubber which transmits more vibration. I had hasport mounts on my old GSR swapped EK that rattled my brain at idle.
2.) Possible MAP issue.

You may want to try cleaning the IACV to see if that smooths the idle out and clears it up. In any case, this is a good idea for maintenance.
Here's a good write up on cleaning it out:

https://www.buzzheadlight.com/idle-a...leaning-honda/

I hope this helps!

 

I know there has been plenty of motor mount talk, but another thing you may not be able to see is if they installed new bushings in the factory mounts. The mounts will look stock, but vibrate like Hasports or any other aftermarket.

 

I have the same issue on my 88 dx auto. After cleaning iacv, double checking vacuum leaks, tuneups, etc. I think it's the torque converter dying. Draining and refilling the tranny fluid a couple times helped a little but I just live with it.

 

Update: Cleaned the IACV, and it made a world of difference. Thank you all so much for the help!