Ok, so my daily is a 1999 Civic LX with an automatic tranny.

Ever since I bought the car around 2 1/2 years ago, I've had a vibration at idle (some might say shaking, but I believe it's more of a vibration). It's slowly become worse over time and now you can undeniably feel it and hear it while sitting in the car. Now, the vibration is continuing to be felt at the end of braking when the car is almost stopped and when you take your foot of the brake and let the car move under it's own power (w/o pressing the gas). It happens in Park and in Drive.

From what I've read around the forum, it could be a number of things...IACV, bad motor mount, vacuum leak, etc. But I'm not sure where to start and don't want to replace things that don't need replacing. I've cleaned several IACVs before, but this intake manifold is different and it's not in the usual place. I'm also not sure if the AT has anything to do with it since all I've had are MT Hondas in the past.

So, what troubleshooting can I do to help narrow the problem down to the source?

TIA

 

When was the last time this was tuned up?

 

Define "tuned up." The air filter needs to be replaced, but it's not in horrible condition, the spark plugs look good and are properly gapped. I change the oil myself with synthetic oil approx. every 7500 miles. Not sure when the tranny fluid was last changed. I replaced all accessory belts last year.

The previous owner bought the car new, serviced it at a honda dealership when he lived in FL and had it serviced at various places once he moved to GA. It had the timing belt replaced around 95k, I bought the car with 98k, it now has 142k.

 

What do you mean "define tune up"? A tune up! A FULL tune up. Cap, rotor, plugs, wires, oil, fuel & air filter.

 

I asked for a definition because every shop/person has a different idea of what a tune-up entails. Anyways, the cap, rotor, plugs, and wires have not been replaced since I've had the car and I don't recall seeing that they had from the documentation the previous owner gave to me.

 

So NO maintenance on it for 44k miles past simple oil changes? Get on it. Sounds like the PO kept up with maintenance. You? Not so much.

Are you throwing any CELs?

 

Lol, I hear ya, a lot has happened in my life during those 44k miles and the DD got neglected. No CELs now or ever...oh and I have also changed the fuel filter, so I'll get on the electrical bits and change the air filter, then report back.

 

Update: On Tuesday night I installed new NGK plugs, NGK wires, oem Honda distributor cap, oem Honda rotor, and an oem Honda air filter. I then reset the ECU and have driven almost 200 miles since. While drive-ability seems to have improved, the vibration is still there.

The car idles at 700-800 rpm most of the time, but will dip down to 500 here and there, however the vibration seems to be about the same at either rpm. If you give it some gas and bring the engine speed to around 1000 rpm the vibration smooths out significantly.
A couple times since resetting the ECU on Tuesday night, the idle dropped extremely low (right at the tick mark above 0 rpm), but didn't die. It first happened when slowing to a stop and then happened again shortly thereafter while sitting at a red light. Obviously the vibration was completely gone at this point as the car was almost "dead".

Any other ideas on what to look for or replace?

TIA

 

Check motor mounts.

 

check your drivers side motor mount.

 

Isn't the driver's side mount oil filled or something different than standard rubber mounts?

What's the easiest way to check them? I had the car in park the other night and revved the motor via throttle cable and didn't see any excessive movement.

 

Finally got around to checking the mounts and they all are fine. I suppose the driver's side mount could still be bad as I'm just not sure how to test it since it's oil filled.

Any other suggestions on what to check?

 

How did you check them? I had a tear in my DS mount that was impossible to see w/o removing the top bracket.

Do you get the vibration in neutral? Did the engine ever have a valve adjustment?

 

Check and adjust your idle speed.

Perform a valve lash adjustment.

 

I just visually inspected them and unbolted the rear mount so I could see it easier.

I don't recall if I get the vibration in neutral, so I'll check for that and as far as I know the car has never had a valve adjustment.

Where can I adjust the idle speed on the LX? The intake manifold is different from other D series I've had and I can't find anything that appears to adjust the idle.

Is there a good write up on valve adjustments? I think I should be able to tackle it myself.

 

The vibration is present in neutral as well.

 

If you are feeling vibrations but the engine is running fine and shifts smoothly via automatic than there is no other possibility but the motor mounts.

 

Now I'm thinking it may have to do with the idle in some way, as it sometimes drops to around 500 rpm instead of staying in the 750-800 range that iirc is considered normal. If you give it slight gas and bring it up to roughly around 1000 rpm is smooths out substantially.

 

this happened to my buddy's 01 ex it turned out to be the motor mounts

 

So bad motor mounts will affect the idle?

 

If your idle is near the zero, the line next to zero than that's five hundred. Might wanna find out why it idles low.

 

Every now and then it will drop that low for some reason, but usually picks right back up. I said 500 because it will often sit between the 0 and 1000, so I figured with the normal rpm being roughly 750 that it should sit between the "500" and 1000.

 

It's okay, I'm just verifying it so you can explain it better. Another thing I wanna say is if you're driving and it vibrayes than it could be your axles. I had that happen on my cousins 4dr civic.

 

It doesn't vibrate when driving except a very low speeds like I explained before. I'm going to pay more attention to when it vibrates as it doesn't have every time I'm idling, but it happens often enough.

 

your idle is low, because you reset the ecu. You need to let the car RELEARN the idle. its obd2 after all. drive the car until its completly warmed up and the fans have turned on atleast once then park it. turn it off and immediatly back on. let it sit and idle for 10 minutes. do not touch the accelerator during this period of time.