rough idle

[chris duke]

can anyone help ?

I drive a 1999 e46 316i SE.

When starting from cold all is fine.

The problem is when the engine has warmed up it has a rough idle, the rev counter bobs up and down and occasionally you can feel the car shudder, it is also noticeable from the exhaust note.

The car drives fine, even when warmed up, having covered 75000 miles and with full service history.

When sitting at traffic lights or at a junction, the rough idle is begging to frustrate me.

I had a diagnostic check on the car at its last service, but this did not pin point anything, infact no faults were found at all ??

My local bmw dealership have not been much help and have suggested i leave it with them for investigation,however they have stated they can giveme know idea of time required to identify underlying issue, and at £105 plus vat an hour i can not afford to have them check it out.

Any ideas or suggestions would be greately received.

Cheers

[anythingfast]

I Could Be Your Iac Valve Sticking Shut Due To Carbon Build Up Sounds About Rite For The Miles Swap In A New One.

[bmw_brendan]

check pcv as they are a big problem on the m43 engine.

[Dudesky_E36]

Although your Idle Control Valve may be dirty, it won't be the culprit. The ICV operates mainly when the engine is cold.

[BAVARIANM]

Crankcase ventilation valve. The internal diaphragm splits

[supervisor1886]

Its clearly missfiring thats why there is a vibration. Its one of your coils going or just as simple as the plugs. Or you loose compression on one of the valves.

Similar condition can caused by what the guys said, but they would be more severe with some stalling issues. Check for any vacuum leaks.

Also all that service history is no use to anyone because many components have equall chances to fail several times or not just fail at all because of the quality and abuse. Its good when your car has 250000 miles on it.

[chris duke]

cheers, for the feed back

Just been tinkering with the car, when i unplug the idle control valve, the rough idle disappears, however the idle sits approx. 9500 - 10500 rpm, i took the car for a run and it is noticeable in the drive that the roughness is gone. When at junctions or parked, etc., the idle is consistent and the needle is motionless, previously it jumped up and down.......

I had the idle control valve off, but it does not look to be too heavily coked, and all internal parts are moving freely.

What components are linked in with, or "talk" with the idle control valve?

Other than the now high idle, would there be any problems with running the car with the valve disconnected, surely it wouldn't be any worse than leaving it as it was.

Is it as clear cut as needing a new icv or could it be linked to something else??

Cheers

Chris

[srs_49]

Did you try disconnecting the O2 sensor? The way I understand it, the O2 sensor's output is ignored until the engine reaches some operating temperature. The fact that the idle is OK when cold, but not when things are warmed goes along with this. At least that's the way things work on my '87 '325.

[Fat Tony]

Hi there I have a e46 320 ci 2001 and have the same problem, but have been quoted for a new cat as i have done 140k apparently its running below threshold so need a new one. (so they say) but is an expensive solution. The problem i have is it costs the same as probably the part just to say what the problem is. might be worth a check. But i might have the same problem as you so please let me know how you get on.

[supervisor1886]

First of all what you doing is not gonna solve anything. By disconecting a sensor or a part like this idle control valve the ECM goes into a limb mode which causes it to remember the last set values for the sensory input or go into lean/ rich condition at idle +the trouble codes to pop out. What you doing is unnaturally forcing it into this mode. This basically rules out the ignition problems, since it idles fine without the valve (probably gting somewhat more fuel or just higher RPMs)

Most IAS failures lead to high or low idle.No roughness. And disconecting it when the engine idles usually causes sudden rise in RPMS from 900 to like 1500.

I think you might have a simple vacuum leak- somewhere-including the crank vent valve, at what the guys already pointed out ^^^^

or a possible lean condition at idle-numerous causes


Check for vacuum leaks

[scoooby]

I own a 1999 e46 316i SE and having similar problems

When starting from cold all is fine, and if i leave the car the revs will be perfectly fine until i drive it and the engine warms up the rev counter starts dancing up and you can feel the car shudder engine vibration.

the engine runs perfectly smooth if i press the accelerator seems like all four cylinder are operational and recently it had a new airflow meter installed by my local bmw dealership, ££££££££

When the car is stationary the rough idle starts to get on my nerves

The diagnostic check on the car revealed no faults at all, i have cleaned the throttle body, new air flow meter, new air filter and new spark plugs but still the car is not right

any suggestions will be helpfull........as the dealership is just a stealership with £200 an hour to diagnose any electrical faults

thanks

[mcalvo]

Did you fix it man? I am having same sympthoms on my 320i e36 (m52). Feedback will be highly appreciated. Thanks.