BMW E36 328i Sport - Erratic Idle

[ChrisDT]

I have a 1998 E36 328i Sport and recently (last 200 miles) it has started to hunt when I am at a junction and on occasion stall. Very annoying - so after a bit of internet doctoring it pointed at either a MAF or a Cam Sensor. I have unplugged the MAF and it doesn't make any difference to how the car runs apart from when I plug the MAF back in it triggers the car to hunt quickly but I put this down to the introduction of the MAF again.
I have also changed the Cam sensor and although it appeared to run a little smoother within 30 seconds or so it started to hunt again on tick over - but no stalling, yet. When the car is shut down (by the key) there is a suction noise from near the MAF, I don't have another car to compare it to so not sure if this is normal. Haven't looked at the CCV yet as I only started reading about this today and i'm not with the car until this evening. It may be the air intake boot but that appears to look ok on the surface and I sprayed bubbles near it yesterday and no signs of a leak.

Plugs appeared ok, but I have a spare set of NGKR kicking about I could change them with but it's not lumpy it's just erratic like it's getting starved.

Any advice would be greatly appreciated at this point as i'm chasing my tail.

[E-bmw]

99% this will almost certainly be 1 of 2 things.

95% it could be the concertina hose between the MAF & the throttle body, you need to completely remove it & try to pull it apart to check for cracks in the valleys between the concertinas.

Additionally, while you are in the are check all vac hoses/connections.

4% it could be an o2 sensor, get it code-read & this will tell you.

Edited by E-bmw on Saturday 15th July 12:20

[e21Mark]

I'd bet on an air leak somewhere. Waft a mist of WD40 over your engine while it idles. If there's any change in idle you'll know there's WD getting in through a leak.

[ChrisDT]

Thanks Guys, i'm going to have another inspection of the hose between the MAF and TB tonight.

I'll put a misting across if nothing else shows up!

[PHuzzy]

Another one to check although usually it is a lot more of an issue is the crankcase vent/breather hose, I had an issue where my car would stall upon letting the revs drop due to it becoming slightly disconnected, check for any splits in that.

[ChrisDT]

Thanks Phuzzy!

[minimods]

This afternoon I replaced the MAF to TB hose and cleaned the ICV on my 530i. Might be in my head but the car seems smoother and idles better. I didn't actually have an idle issue, it was more preventative maintenance. Anything rubber on this age of car is bound to require renewal so it is worth it for the small outlay and 10 mins work.

[ChrisDT]

For what it costs I have ordered one, mine has a very small mark on it that could be causing the issue (Probably isn't but ...) so lets see what that does - seemed excessively bad yesterday!

[B234R]

My car had the same problem a few months ago, and the rubber intake hose was almost new. I changed the cam sensor and the problem was solved. I used a VDO Siemens sensor, is it yours OEM/VDO Siemens, or another brand?

[ChrisDT]

I used a Delphi one which from research also make for BMW

[ChrisDT]

Incase anyone is wondering, carried out a smoke test and no leak was found, replaced the MAF with another - Not 100% this is a working MAF so going to try and put on a working MAF from another car and see if that fixes it. Also removed and cleaned the ICV and refitted, checked connections all good, tested the CCV with the baloon test and this was fine, replaced the O2 sensor (As this came up on the diagnostics) and car still remains the same - also replaced the Plugs, and the valve cover gasket (This was well past a change required). Car runs a lot better but still has the erratic idle. Still has the O2 sensor code in the ECU and comes back as soon as it clears. Car also runs a lot better with the MAF disconnected so i'm hoping (in a bizzare way) that the MAF I bought was either faulty or on it's last legs.. With a new one being so expensive I need to try with a known working one to see if it's the root of my issues. Can't fault the car when it's driving - drives like a dream.

[BGarside]

Failing cam sensor caused erratic idle and stalling with my 328i. Also jerky power delivery when driving gently from cold.

[E-bmw]

I may be wrong & it is still worth doing if not already, alas I have my doubts.

The electric (in-tank) fuel pump flows x litres/min from the moment the engine starts.

The fuel pressure regulator at the engine end regulates the fuel to the required pressure when it is running (3 or 3.5 bar, I forget which) so I can't see why the fuel filter would cause fuel starvation at idle, which is when the fuel requirement is at its lowest.

I forget, have you checked for inlet boot/vac leak yet?

What about Vanos seals?

[E-bmw]

I assume you reset that after fitting the new one then?