E30 Idle Problem - Please help, in despiration!

[bmwe30mtech]

Hi all, I have posted this before and had various ideas, but this is how it stands:

My car wont idle, and never has done in my ownership, its an M40 318i and i have finaly been driven crazy by the inablity for it to idle. It cuts out at traffic lights etc, when i change gear, and constantly hunts, but doent find it and stalls. I have done:

Cleaned old ICV - Worked for about 10 mins, then went bad again,
New ICV - Worked for a week, then went bad again,
New AFM - Worked for a week and then went bad again,
Another AFM - Worked for about 10 mins, then went bad again,
All new gaskets in the manifold and bulkhead (unrelated but its been done)

I am so fed up, BMW could not fix it, and said 'it returned to this irregular ilde after they adjusted a few things'. I dont now what the next move is, but its the ONLY broken thing on the car so realy lets it down.

Try a different ECU?? CAN I JUST ADJUST THE CABLE INTO THE THROTTLE BODY?? I realy dont have a clue anymore, i have checked it over so many times. Its an embarasment in town etc. When i start it i hvae to have my foot on the pedel or it will instantly stall.

Many thanks to any help or advice

Paul

[Andy325i]

ECU maybe a good plan, if you can borrow one. Also check the CO level

Hand in there. Hope you get it sorted dude!

Andy

[bmwe30mtech]

Thanks Andy.

I dont know how to change an ECU. Are they all the same for M40's, and is it litrually a case of plugging it in as 'one unit'? Dont know if any body has one lying arround..?

Paul

[Jon_Bmw]

Steve tigger might have an ECU, as his m50 engine aint going to respond to well to an m40 ECU. I'm sure he'll also remind you it came from a 74k fsh m40 car

Sorry to hear about yur problems, brain moore will probably give you the best advice, i know nothing about the m40 engine, so i'm no good

Free bump

[Globulator]

On the M20 there is a seperate idle computer that runs the ICV.
Your system may differ.
Check the throttle switch - it switches the system over from the main ECU to the idle computer - if it is not switched over it cannot function.
Check for air leaks - try clamping/tyrap the pipes if they seem loose on the ICV connections.
Check for split rubber anywhere on the inlet tract.
Make sure the fuel pressure regulator works.

[Andy335Touring]

Like said before try testing the TPS and check all electrical plugs for rust/dirt/etc.

Sorry i haven't got any experiance working on an M40,they are just general ideas to try.

[rickk]

To me it sounds like it just runs way too rich. That would cause exactly that behaviour. Likely suspects are the coolant temp sensor and O2 sensor (if you have one).

Is it better when the car is cold?

Good luck,
Rick

[bmwe30mtech]

Thanks for the suggestions, i will be trying those tomorrow. As for a ECU i will talk to some friends.

The car is far worse when cold, for a while it was actualy idleing when warm! Where are these sensors i need to check located?

Also whats a TPS?

Many thanks guys, hopefully i can finally get to the bottom of this one soon,

Paul

[Andy325i]

Thanks for the suggestions, i will be trying those tomorrow. As for a ECU i will talk to some friends.

The car is far worse when cold, for a while it was actualy idleing when warm! Where are these sensors i need to check located?

Also whats a TPS?

Many thanks guys, hopefully i can finally get to the bottom of this one soon,

Paul

Right, there are 2 temp senders, the blue one tells the ECU what temp the engine is, (Cold, warm or, fully up to temp iirc) and hence how much fuel to dump in to the engine (think of it as a clever choke system)
It does this by altering the resistance with temp. When these play up they dump far too much fuel in usually and hence it won't idle without being reved.

Iirc the M40 one is in the thermostat housing??? or maybe in the side of the head near the front under the inlet manifold

If your ok with electrical things you can measure the resistance of it at set temps to test its operation.

These are about £10 from ECP or GSF or a little more from the stealers.

I will post the values you should get up later, when I have my bently manual to hand (if someone doesn't beat me too it )

The other temp sender is a brown one and simply operates the temp gauge in the speedo head - no need to worry about this one.

TPS - Throttle position swich

This tells the ECU what is happening with the Throttle butterfly

Iirc (Again!) it has 3 states (not constantly varible) Idle, somewhere in the middle, or pedal to the metal. This changes the Map it uses in the ECU.

Idle, not really sure tbh

Normal - Normal map

Pedal to the metal - forget emissions or fuel economy, this map is purely for getting it going quicker!

HTH

Andy

[Ant]

PM me your details dude, and once I get my Wideband 02( MR Demlot ) back I'll venture over and take a peek.

[Brianmoooore]

TPS is the first thing I would check/change - but if its been to BMW, then that's the first thing they should have checked.

[Brianmoooore]

[
Iirc the M40 one is in the thermostat housing??? or maybe in the side of the head near the front under the inlet manifold
Andy

M40 blue temp sensor is immediately under the middle of the inlet manifold.

[bmwe30mtech]

Thanks very much guys, and Andy such a helpful and long response . Ant, i have sent you a pm with my number.

Thanks,

Paul