M42club.com - Home of the BMW E30/E36 318i/iS
DISCUSSION => Engine + Driveline => Topic started by: ClassicSkril on December 03, 2010, 03:46:51 AM
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My car has been idling strange since I purchased it a while back. Got all the belts replaced, and did the fuel filter, and in addition the mechanic said I did not have a vac leak. Several hoses have been replace since then and the car still idles strange about every other time I drive it. It drops to 500rpm, then after a second it bounces up to a thousand. Any thoughts? It resurfaces, sometimes I don't have this issue, then it returns. Also I have no power loss issues when driving.
91 318IS
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I'd clean & test the idle control valve to start. Might be that. I'd also double-check the main intake hose for cracks and the hoses under the main intake tube. Did your mechanic do any tests, like a propane gas cylinder, or did he just do a good look-over? I've found that those hoses really like to leak, and it's difficult to find leaks.
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Thanks for the tips I will definitely try that. I have heard people say the main intake hose can be cracked and still look brand new. I did replace a small hose beneath it which was cracked. The previous owner had a ghetto short ram setup which caused the intake hose to sag and the MAF to have a downward angle which isnt good. But yea my mechanic said he did the spray test and there isnt a vacum leak. where on the intake hose does it normally crack?
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Mine cracked around the hose clamps on both the AFM and the TB. I used a little black RTV and electrical tape to patch it temporarily a year or so ago. You can test the ICV by feeling if it vibrates when the motor is running. I've also tested it by pulling the harness & using a 9v battery with flying leads.
A good penetrating oil like SeaFoam Deep Creep or PB Blaster should clean it up nicely if it's sticking. Try to keep the oil in the valve body though, I've heard it's not good to get it into the motor mechanism. I brought one back on an M20 eta by soaking the valve body with Deep Creep, stood it on the valve body (motor end up) and let it dry pretty well before re-installing it.
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thank you very much for all the suggestions. I will try these and see how things are looking
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I did some searches on write-ups for removing and cleaning the icv, as I have never done this. The entire intake manifold must be removed correct?
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you dont have to remove the manifold all you have to do is remove the 10mm bolt and it comes right out just disconnet the two hoses that are attached to it and clean away with you cleaner of choice its a very simple job
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Ok thanks. And it is located under the manifold towards the fire wall if I read correctly?
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its not under the manifold its behind it you should be able to see it with the hood open if you look on the back of the the intake manifold there is a hose connected to it and that hose connects to the icv
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I wish I could find some pictures on here of this. I'm sure there are some just haven't had any luck.
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I removed it last night. It was a little awkward due to the tight space but I managed. It was dirty, but what was worse is there is a split at the end of the tube that connects to the bottom of the ICV. So needless to say I think removing the manifold will be next to replace all my lines under there, if my idle doesn't improve
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fyi you dont have to remove the manifold i didnt just remove the intake boot and you will have nice access to all the lines i bought 19/32 hose from auto zone and fitted hose from carquest for like 7 bucks that connects to the bottom of the icv and used the existing plastic tees to make things fit again total investment was like 15 bucks to fix the mess
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fyi you dont have to remove the manifold i didnt just remove the intake boot and you will have nice access to all the lines i bought 19/32 hose from auto zone and fitted hose from carquest for like 7 bucks that connects to the bottom of the icv and used the existing plastic tees to make things fit again total investment was like 15 bucks to fix the mess
whoa nice. so to replace that lower hose I can actually do with non oem hoses? and without the manifold being removed? the only write-ups I have seen were with it off
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I cleaned my icv and I am still having idle issues. Is it likely to be a vaccum line issue or could it be something totally different like my alternator?
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Im having a similar problem with my 95 318is although its not intermitent and havent solved it yet, however these are the things ive looked at so far
check your airflow meter ( AFM) you can take that off and make sure the flaps opening freely but if its an electrical fault youll need to replace it. The other thing is the throttle position sensor, located on the throttle body this tells your ecu how much fuel to dump and may be sending the wrong signal? 1 more option is the Lambda sensor located on the exhaust under the car, this is another fuel/air regulator and that too could be worth checking.
Hope that helps
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Im having a similar problem with my 95 318is although its not intermitent and havent solved it yet, however these are the things ive looked at so far
check your airflow meter ( AFM) you can take that off and make sure the flaps opening freely but if its an electrical fault youll need to replace it. The other thing is the throttle position sensor, located on the throttle body this tells your ecu how much fuel to dump and may be sending the wrong signal? 1 more option is the Lambda sensor located on the exhaust under the car, this is another fuel/air regulator and that too could be worth checking.
Hope that helps
those are some possibilities. The thing that leads me to the icv possibly being faulty is when I cleaned it, it ran great for like a week or so. Now it's back which leads me to think it is getting stuck. I will try cleaning it again but I'm thinking I will need a new one. I plan on doing the mess under the intake mod but this issue seems to revolve around the icv
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It could be the icv then, one thing ive learnt is the car is more intelligent than you think and when you change or disconnect something it normaly componsates elsewhere to keep it going.. Ie, disconect the electric wire on icv it will hunt slightly but wont surge, do the same with airflow meter and itll do the same thing.. I found it strange that when i opened the oil filler cap that made my m42 idle perfect, thats the engine trying to compensate for air change, weird! Lol..
Anyway i fixed mine last night, it turned out to be the lambda/02 sensor.. Good luck mate
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It could be the icv then, one thing ive learnt is the car is more intelligent than you think and when you change or disconnect something it normaly componsates elsewhere to keep it going.. Ie, disconect the electric wire on icv it will hunt slightly but wont surge, do the same with airflow meter and itll do the same thing.. I found it strange that when i opened the oil filler cap that made my m42 idle perfect, thats the engine trying to compensate for air change, weird! Lol..
Anyway i fixed mine last night, it turned out to be the lambda/02 sensor.. Good luck mate
cheers! Glad you got yours fixed. My battle is not over yet, everyone keeps telling me "vacuum leak vacuum leak" but if that was the case it would do this all the time? So I have a feeling the icv is going out. When I cleaned it (the first time it's ever been cleaned I'm sure) it ran great and when the idle tried to drop it corrected itself like it should. After a week or so the problem returned. I think the mechanism inside is getting stuck
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thanks bud, well a new icv isnt too expensive and also if you hold the icv while plugged in and turn the ignition on it should vibrate if its working.
Everyone everywhere told me it was a vacuum leak but id checked everything, the only reason i decided on the lambda sensor is because apparently they're meant to be changed every 30,000-50,000 miles and my car had done 84,000! plus it was in a sh*t state to look at lol.
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thanks bud, well a new icv isnt too expensive and also if you hold the icv while plugged in and turn the ignition on it should vibrate if its working.
Everyone everywhere told me it was a vacuum leak but id checked everything, the only reason i decided on the lambda sensor is because apparently they're meant to be changed every 30,000-50,000 miles and my car had done 84,000! plus it was in a sh*t state to look at lol.
haha well im glad you found the culprit! I am gonna do the mess under the intake mod soon and try another ICV hopefully and replace my temp sensor and if it persists.....i will try the o2 sensor.