Lots of maintenance/repair done... car still rough

[AutoM3otives]

So when I got my car I repaired the following items:

engine mounts
tranny mounts
rear shocks
rear shock mounts
flex disc
exhaust hangers
air filter
oil change
spark plugs
magnecor ignition wires
front O2 sensor replaced, rear untouched
(checked fuel filter- its fine)

and I just did the infamous ICV cleaning...

and that didn't help either!
when in gear at idle, the engine vibrates and it goes through the rest of the cabin.

also, I compared the exit of the exhaust gases of all our cars when at idle. The M3 and the benzes all release the exhaust smoothly, but the Ti shoots it out every second like BOOF BOOF BOOF BOOF.

anything else I can do to fix this madness?!

[aceyx]

what kind of exhaust do you have? it could be a (lack of) backpressure problem--exhaust gas flows to quickly, creating "gaps" between exhaust pulses--in which case you'll probably want to check for leaks, etc, including the gasket for the exhaust manifold.

since the vibration only occurs when in gear (does it happen in reverse?) i would check the clutch. it might not be releasing fully which means a slave cylinder bleeding. if this is the case, the pressure plate should be worn down more than the clutch disc (i think, it could be the opposite way around).


is the engine vibration constant or does it change with rpm?

is the exhaust only like this in idle? (drive with your windows open, and pass a brick building) off the top of my head it's not abnormal for the motor to do this in idle.

[AutoM3otives]

oh yea forgot to mention in my initial post...

ever since I got the motor and tranny mounts installed... the heavy vibration occurred. it would shake the whole lenght of the exhaust under the car, and as a result of that vibration it would hit the underbody of the car and that vibration would translate violently into the car.

do you think the replacement of new mounts raised the drivetrain to the point that it touches the underbody?

aceyx:

yes the vibration occurs when in reverse, but when you speak of a clutch, i failed to mention that the car is an auto.

the engine/exhaust vibration only occurs when at idle.
as today, after I did the ICV cleaning, I drove the car. When on the freeway, the car was as smooth as silk, but when i would slow down for a stop, the revvs would fluctuate between 500-1000 a couple times, like it wanted to stall.

[lkwd318ti]

Hey AutoM3otives,

I had that exact same problem a month or 2 ago too!
Here's the thread (http://www.318ti.org/forum/showthread.php?t=5070).
The RPMs on my car went as low as 200 RPMs (at least thats what it looked like on my tach).
My car made that BOOF BOOF BOOF BOOF sound too...like it was an old broken up car haha.
I just brought my car to the dealership and they told me that they just did a little reprogramming and I think that they adjusted my shift linkage (I think).
I think my dad also asked them to do an oil change too because we though that was the problem too.
Ever since, I haven't had a problem, as a matter of fact, I think that it drives smoother (I don't know if this will make a difference, but I drive in manual mode all the time).
Well, good luck on the whole thing.

-Randy

[aceyx]

if the revs are fluctuating it may be a vacuum leak.
EDIT: lkwd seems to have a more fitting diagnosis.

are the mounts stock or aftermarket? one thing i would do is (with the car running, in neutral) open the hood. the motor really shouldn't move at all. i'm not talking dead like a doorknob, but just smoothly humming. since you've got the idle problem, i would have someone on the pedal to keep the revs at 1000 or whatever, just keep it even.

- if the motor is being a bad monkey, you will see it thrash about.
- if the motor sits quietly, the problem is in the tranny.

[AutoM3otives]

lkwd318ti:
thanks for the tip. I'll look into it.
oh yea, how much did the dealership charge for the fix? can you find out the exact details of the repairs they did for your Ti?

A general question:
does anyone have a smooth running, perfectly idle 318ti? does such a thing exist? ever since my gf got her Benz C230K coupe, her car's engine is so smooth that I am in the pursuit of a smooth m44 engine.

[lkwd318ti]

lkwd318ti:
thanks for the tip. I'll look into it.
oh yea, how much did the dealership charge for the fix? can you find out the exact details of the repairs they did for your Ti?


Hey man,
If I remember correctly, I think that I spent less than $300 on it. I was pretty much surprised because I was expecting to pay WAY MORE.
Oh yeah, when you drive your car, has that orange light with the little gear light up? My dad told me that when he drove my car to the dealer, that light went on and stuff.
My dad also told me that when the car downshifted, there was metal clanking sound (he drove it in automatic mode whereas I drive in manual, so I didn't experience that sound).
One more thing, is the engine rough at idle ALL the time, or only on occasion?
For the exact details, I'll try to figure out what they did to my car, I'll try to find the reciept for the service when I get home.
I'll get back to you ASAP
-Randy

[KdCass]

Some said vaccum leek I agree. I had one and the car was hard to start then ran like that at idle.

-Dave

[lkwd318ti]

Hey Autom3otives,
I just remembered something that the people at the dealership told me.
They told me to check all the hoses you can see on the engine bay. Look for cracks and stuff.
Sorry, but I haven't found my reciept yet, but I'm pretty sure I spent under $300 hehe.
I'll get back to you again if I remember anything else or if I find the reciept.
-Randy