M44 idle problem.... need help asap

[96CosmosM398TI]

i just picked up a 98 318ti... and the idle sucks, it keeps hesitating and its around like 600-700 rpms. ive changed the plugs, cleaned out the idle control valve, sprayed starting fluid to check for vacuum leaks nothing....still idling rough.. i am not pulling any codes as of yet due to the battery being disconnected but i know i had a CEL before. basically i am stuck in between a rock and a hard place right now cause i need to get all the bugs out to pass emissions and i know it wont pass. when running the thing smells bad too, cant really explain the smell but its not pleasant... anyone any ideas? the thing has a smooth power band and is peppy, even more peppy than my fathers 318....

[weezer]

Did you check the most expensive item: the plug wires?
I had an issue with this about a week ago; one of the rubber boots is frayed and creating an arc and one cylinder was misfiring; i replaced the wires ($80 for magnecors, $180-200 for OEM) and the problem went away. The idle should be no more than 600-750 rpms. Check for leaks in the intake plenum/hose around the throttle body, MAF hose, etc. Fuel filter sometimes could be the culprit ($121 OEM) located underneath the car just under the driver; that should also be replaced every 30-60k also.
If there's fuel odor in the car when tank is 3/4, it could be the O-rings on the fuel tank caps underneath the rear seats. If there's fuel deposits, that's the sign; fuel odor could also mean the fuel pump is working too hard because of a clogged fuel filter.
Unfortunately, it's a process of elimination, so be patient and good luck.

[96CosmosM398TI]

yea the wires seem whole and dry, but not dry rotted or anything... and all the old plugs had an identical color as well... so i am assuming it is firing correctly, like i said though i sprayed starting fluid along all the vacuum lines and i did not notice a change in idle, i had the upper manifold removed , and i did notice it was a bit dirty, but the car has 120K so i dont expect to be able to eat off of it... anyways i am stumped because it doesn't seem like a vacuum leak or plugs, and its running premium (93) but still idles rough....

[weezer]

yea the wires seem whole and dry, but not dry rotted or anything... and all the old plugs had an identical color as well... so i am assuming it is firing correctly, like i said though i sprayed starting fluid along all the vacuum lines and i did not notice a change in idle, i had the upper manifold removed , and i did notice it was a bit dirty, but the car has 120K so i dont expect to be able to eat off of it... anyways i am stumped because it doesn't seem like a vacuum leak or plugs, and its running premium (93) but still idles rough....

Try replacing the fuel filter and see what happens......it's all a process of elimination, unfortunately.
Any of the plugs coated with oil when you changed them?

[96CosmosM398TI]

nope valve cover gasket is still good surprisingly...

[weezer]

yea the wires seem whole and dry, but not dry rotted or anything... and all the old plugs had an identical color as well... so i am assuming it is firing correctly, like i said though i sprayed starting fluid along all the vacuum lines and i did not notice a change in idle, i had the upper manifold removed , and i did notice it was a bit dirty, but the car has 120K so i dont expect to be able to eat off of it... anyways i am stumped because it doesn't seem like a vacuum leak or plugs, and its running premium (93) but still idles rough....

Now, when you rev the engine, does it tremble?
When driving does the engine hesitate around 3000-4000 rpms?
The plug wires might look fine, because you can't see the fray/hole on the boots. When the engine is running try unplugging the spark plug wires one at a time and plug it back. If the engine stumbles when one plug is out that wire is okay. But when you unplug one of the plugs and the engine still runs the same way, there's a problem with that plug wire.
Good Luck

[Anth2006]

Where is the idle control valve located, i have the same problem with my idle,
especially when its cold.

[96CosmosM398TI]

the car drives like a champ ... no hesitation, it is just the idle that is rough, reving it in neutral feels normal no hesitation....


The icv is right next to the throttle body its black about 2" by 2" big has a 3 prong connector on it as well if i have some time i will try to find a pic of it ... if not do a search thats how i found it, it was in another post

[Anth2006]

Thats great thanks,
I will check that tomorrow and clean it out.

[cooljess76]

Check the oil cap!!! if your oil cap is not on properly, and yes it is possible to put it on crooked with only one side secured, your car will idle really rough.

[96CosmosM398TI]

nope thats fine to lol, but yea i do know what you are speaking off....

[JNCoulombe]

I suggest trying the Seafoam treatment. I did this last weekend and it now idles and generally runs much much better. This is definitly worth trying for $7. You will need to reset the codes or live with the check engine light untill the misfire codes reset themselves. I would also suggest doing the treatment after dark to avoid frightening the neighbors. Smoking down the road for a couple of miles is rather embarassing.