O2 Sensor or motor mounts?

I've posted here before about this problem and was fairly sure that I had bad motor mounts causing vibration at idle in both Drive and Reverse. However, someone mentioned that the O2 sensor could cause rough idle as well. I have noticed the exhaust smelling strong for sometime now but not necessarily like the "rotten egg" smell.

Could a bad O2 sensor be my vibration problem? Note that the vibration is only when idling the car in Drive, 2, 3 or Reverse. Also, if I'm sitting at a red light with the car in neutral and shift it down into Drive, I notice a large vibration through the car immediately shifting into Drive then it goes away leaving only the surge type vibration....meaning you can actually feel the vibration surge through the vehicle every second or second and a half or so. There is hardly vibration when idling in Park or Neutral though. Would bad motor mounts still idle rough in Park and Neutral?

Thanks for your time and your comments would be appreciated. Thanks.

1994 Saturn SL2 DOHC

Its not usually the 02 sensors, but the EGR. Clean yours and remove all the carbon deposits. See if that helps. After that, you can unplug the EGR and see if that helps. It could be a dirty EGR or a malfunctioning EGR

Its not usually the 02 sensors, but the EGR. Clean yours and remove all the carbon deposits. See if that helps. After that, you can unplug the EGR and see if that helps. It could be a dirty EGR or a malfunctioning EGR

I should be able to rule out the EGR valve since I just replaced it a few months ago...

Also, do you know if Advance Auto Parts or any place like that can test to see if the O2 sensor is bad or not? Do they usually charge for a test like that?


Thanks.

There is no real test. The only thing is to watch the output voltage of it on a scanner that supports real time data. I would double check the egr though. Ive seen some get fualty ones that were new.

Also, have you changed the ECTS to brass?

There is no real test. The only thing is to watch the output voltage of it on a scanner that supports real time data. I would double check the egr though. Ive seen some get fualty ones that were new.

Also, have you changed the ECTS to brass?

Alright. How do you go about checking to make sure the EGR valve is working properly?

Unfortunately I haven't changed the ECTS to brass. Would that have anything to do with the vibration? I haven't noticed a coolant problem though...

Thx

A bad ECTS can lead to a rough idle thus give you your vibrations. this should be changed out first before anything else.

To check the EGR, unplug the connector and drive it around. Youll get an SES light on but it can be ignored for now.

Another thing i forgot to ask is did you retorque the other 3 mounts after you did the top motor mount? If you did not this can lead to even worse vibrations than before :)

A bad ECTS can lead to a rough idle thus give you your vibrations. this should be changed out first before anything else.

Hmm, I'll definitely have to look into replacing this then. It doesn't appear hard to replace...assuming this (http://www.saturnfans.com/forums/showthread.php?t=37884) is pretty much the way I would go about it with my model. Do you know how much one of these usually runs and I guess I could get one from a local auto parts store since I'm not close to a dealer?

To check the EGR, unplug the connector and drive it around. Youll get an SES light on but it can be ignored for now.

I actually tried this before when I was trying to see if if the original one was bad. Although I'm pretty sure that unplugging this didn't help the vibration at all and honestly with the new EGR valve I still get some bucking when accelerating - that's what I was mainly trying to fix when I replaced that...I know a little buck is normal but sometimes it seems like it does it too hard...the valve looked good when I put it on so hopefully it isn't bad. I'll experiment with unplugging it again though and see if I can tell any difference anywhere to make sure.

Another thing i forgot to ask is did you retorque the other 3 mounts after you did the top motor mount? If you did not this can lead to even worse vibrations than before :)

I did retorque the dog bone engine mount on the lower passenger's side but I didn't touch any of the other ones so I'll check into retorquing them although I'm guessing they need completely replaced at this point. Basically I'm just trying to figure out what is mainly causing the vibration though and replace only what is need right now since money is tight...especially this time of year.

Thanks.

Yupp that link is a good how-to. Sensor is 20 bucks at the dealer and 10 at the auto store. Youll need teflon tape also if you get it from the autostore though.

Definetly retorque the other mounts. Replacement may not be needed for them.

Yupp that link is a good how-to. Sensor is 20 bucks at the dealer and 10 at the auto store. Youll need teflon tape also if you get it from the autostore though.

Definetly retorque the other mounts. Replacement may not be needed for them.

Sorry it's taken me so long to reply but I haven't had much time to work on it. Anyway, I bought and replaced the ECTS today as you said though. As for re-touring the motor mounts, I haven't gotten around to doing that yet. Is there any certain procedure I should use when doing that or just loosen them a little one by one and re-torque each right after loosening?

Also, I'm thinking about draining/flushing my coolant system soon. Is the drain plug for this underneath the passenger's side somewhere and does the plug come all the way out? When flushing the coolant system, I guess you can just run water through the overflow tank with the plug still out?

Thanks.

Nope just loosen all the bolts for the mount and retorque them. Do not just loosen one and then tighten it again. All of the bolts have to be loosened, then all re tightened :)


There are two drain holes. One on the radiator on the passengers side. This is plastic and it turns and pulls. It does NOT come all the way out. Removal of the Air deflector is helpful but not needed. There is also a 10mm bolt where the thermostat is, access is from under the car. This drains the block.

A proper fluid flush has a little more detail than just running water through the system. I can post a how-to for this if needed.

Heres how to change the ECTS :
http://www.youtube.com/watch?v=JC0U53w_Htk