Mazda 626 voltage draw causing rough idle.

[efreakingt]

My womans car is a 2000 626 4 cylinder. I'm trying to figure out what would be causing the motor to run so rough.
It had always been vibrating a lot at idle but heres what happened..

For a long time now the car has had bad motor and trans mounts (3 of 4 needed replacing). We just had those replaced and now the vibrations have become unbearable. Its like the car is going to shake apart some times.

I just checked it out for the first time myself today. It idles rough to begin with, a very fast steady rough, though not a jumpy sporadic rough. Kicking on the A/C made it shake really strong so I turned that off. I noticed now that even just the vents running makes it run a tad rougher, I turned that off. I tried the hazard flashers and that makes the roughness dip up and down slightly to the beat of the flashers.

So obviously my initial conclusion is that the voltage is not strong enough on the car. I check the voltage at the battery and its holding steady 14.20v with very little on and only drops to 14.12v at worst when A/C is running.

Is this possibly a bad alternator or is this all just coincidental after effects of a poor running motor? Any suggestions on what I should look for or check would be great.

 

[SteveSter]

Anywhere from 13.5 to 14.5V is a good range to have an alternator charging at. You should go get it checked for free at autozone or advanceautoparts etc. Im not sure if your 626 has a distributor but if it does you may want to try to adjust timing. If not you may want to check your ignition system and make sure its giving the spark it needs to give. Other simple things you may want to check is a vacuum leak. A vac leak would cause a high rough running idle, its usually pretty audible so check around. A good way to test for a leak is to get a small can of propane, open it but DO NOT LIGHT IT and aim it towards different parts of the engine if you aim towards a particular area and the idle goes up then thats where your vac leak is. Check for fouled spark plugs.

 

[efreakingt]

So far I have checked for vac leaks with some carb cleaner all around the motor, didn't find anything that way. I cleaned the throttle body some which helped it just a little bit.

I haven't gotten in to get the alt and battery tested yet, also haven't pulled the plugs yet. I don't think there's a distributor, if there is I'm not aware of it. There is a ignition coil that has all four plug wires going to it and it looks kinda old.

Its running fine when driving, its only shaking really bad when it hits idle range. Its showing idle on the tach of one quarter below 1000 so I believe that's in proper range. I checked the PCV and it seems to be operational. My next suspect would be possibly the EGR but I'm not quite sure how to test it.

After cleaning the throttle body the shaking is a lot less violent but still present none the less.