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Forum LockedIdle problems with 3.0L E36 M3, VANOS?

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teddie View Drop Down
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Direct Link To This Post Topic: Idle problems with 3.0L E36 M3, VANOS?
    Posted: 20-February-2005 at 03:57

First of all, i'm not from UK but i've been reading your forum for quite some time and it seems like there's lots of expertise here. I have a big problem with my S50B30 engine M3 (-93) and I thought maybe someone here could have some ideas..

The problem doesn't appear always, it was off for like 2 months after the main dealer "cleaned some terminals" and such but now it has started appearing again. The symptoms are that idle drops to 500-600 rpm and car shakes and splutters. If given some gas the shaking goes away but there's still some spluttering. When driving it seems perfectly okay when not in idle.

It's been to the main dealer for 4 times now because of the same problem and I've spent a lot of money changing this and that but they really can't figure out what is causing it. If i let the car idle, it might do it for 5 minutes and then suddenly start idling perfectly again. The only thing the mechanic at the dealership could figure out was that it could be something to do with the VANOS being in improper position and thus causing what appears like lost compression(intake valves open too much). Compression test showed all cylinders good.

What I would like to know is how the VANOS works on the 3.0L? Is it a three stage system? So that it is same in idle and high range and different in middle rpms? How does it change the timing in middle, to which direction?

And should it be "de-energized" on idle? So if one would take off the control plug of the VANOS unit, it should idle perfectly and then have problems on the middle rpms when it should be activated? Haven't had the guts to try this yet, so is it safe and a reasonable idea to try?

Could it be an ECU problem? I'm trying to find a salvaged ECU from a similar car to try. Does the main ECU control the VANOS or is there an another one?

Thank you for any possible ideas regarding this! It's been such a pain in the ass for so many months and I haven't really had the chance to enjoy the M at all :(

- Teddie W

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Stone-IslandV8 View Drop Down
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Direct Link To This Post Posted: 20-February-2005 at 08:15
Could be a variety of things ranging from ECU to a sensor-lamda,throttle position sensor or idle control sensor etc, to plugs.

Try a quick test-disconnect the cars battery and leave it disconnected for 30 mins or so. Then reconnect and start the car and let it idle for 30 mins or so. To do this properly then you should drive the car at steady 50-60mph for 30 mins but do the quickie fix 1st. This resets the system and lets the ECU reacquaint itself with all the sensors. If its a clog in the system then this should clear it if not get a diagnostic kit plugged into the car and see what that throws up.

Bear in mind the process above will clear any stored error codes in the ECU.

John
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Past; E39 540T/E46 328CI/ E39 535/ E39 520/ E36 M3/ E36 318iS jet black Mtech/ E46 320d/ E36 318iS diamond black/ E36 318iS blue Mtech kit
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Direct Link To This Post Posted: 20-February-2005 at 10:48
Thanks for your input John. I will try the disconnecting tomorrow.

Car has been in diagnostics many times and only thing that shows up is "Knock sensor test-pulse failure". Both lambda's have been changed, ignition coils have been checked, camshaft sensor has been changed, plugs have been changed.. all this to no avail :(

Could someone tell me what would be done if the VANOS control unit would be disconnected? In which state the cams would then be in?
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Direct Link To This Post Posted: 20-February-2005 at 14:09
What about the throttle position sensor or the idle control sensor? When it went in for work did anyone mess around with the throttle cable...I know this won't alter the tickover but might be worth checking to see if its running excessive slack.
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Past; E39 540T/E46 328CI/ E39 535/ E39 520/ E36 M3/ E36 318iS jet black Mtech/ E46 320d/ E36 318iS diamond black/ E36 318iS blue Mtech kit
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Direct Link To This Post Posted: 20-February-2005 at 14:47

What is an idle control sensor? Where is it and what does it measure etc?

 Will have the throttle position sensor checked asap. Throttle cable seems to be ok.

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Direct Link To This Post Posted: 20-February-2005 at 15:36
Sorry Teddie meant the idle control valve which is located on a bracket under the inlet manifold.
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Past; E39 540T/E46 328CI/ E39 535/ E39 520/ E36 M3/ E36 318iS jet black Mtech/ E46 320d/ E36 318iS diamond black/ E36 318iS blue Mtech kit
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Direct Link To This Post Posted: 20-February-2005 at 16:48

Hi Teddie,

Firstly I tend to read these posts in a bit of hurry, short attention span.......so I may have missed something.... but I'm concerned your car is showing "Knock sensor test-pulse failure" and it sounds as though nothing has been done about it?? Correct me if I'm wrong but isn't this referring to the microphones attached to the block to detect "knocking".

The purpose of these are to alter the ignition timing should the engine start to "knock". If they are faulty you 'may' get a signal equivalent to engine knock causing a modified ignition curve and that would upset your idle, particularly as there are three from memory and the ignition curve is adapted on the offending cylinders, or in your case the offending sensors.......although I'm suprised your dealer hadn't sorted it.......

Dave.

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Direct Link To This Post Posted: 21-February-2005 at 04:27

Dave, I have been wondering the same thing but the dealer has assured me that this error is not a concern..

They say the test-pulse thing is about a ECU self test and the error is recorded during startup(RPMs like 250rpm = starter). So this is also why they want to try a new ECU.

Does someone know the part numbers for the knock sensors, I can't seem to find them in the ETK?

I will try all the things discussed here during this week and report back here. This has been going on for too long and the dealer doesn't really know what to do so I guess I have to sort it out myself :)

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Direct Link To This Post Posted: 21-February-2005 at 14:54

Hi Teddie,

Please check, but from my info the part numbers are:

12 14 1 738 667, 12 14 1 401 238, 12 14 1 401 187

......price around £47 each inc VAT here in UK. The correct description is 'Ping Sensors' and there are 3 off in total.

...before you buy them carry out a simple check. Get the dealer (or do it yourself) to disconnect/unplug the sensors completely from the loom, (make sure they don't just unbolt them from the cylinder block and leave them connected to the loom) and leave the car to idle.... see how you get on...... best of luck.

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