Idle issues, help on setting up

[Duncmasterflex]

Hey guys
So I've had the 325i on the road a month or so now, gently running the rebuilt motor in and currently got 240 miles on her, haven't been taking her over 3500rpm and planning on getting to 500m and changing oil and filter before I give her the beans. Everything on the engine is new, I've polished and ported the head and running a BBTB so I don't expect idle to be particularly special, and I haven't gotten around to checking continuity at the throttle position switch, as I'm guessing it may be a little out after having the throttle body bored and rebuilt?
On reading the Bentley manual it says that idle and fuelling are all controlled by ECU and it takes info from TPS , temp sensor (new from BMW) and O2 sensor (don't have one on my s/s 3-1 manifolds) so am I right in guessing this puts it in a rich fuel map? And if I gently adjust the TPS with the multimeter attached and get the ohm values where they should be I'll have a decent idle?
Rotor, dizzy, leads and plugs are all brand new btw. Currently got her idling on the throttle stop screw.
Failing this is there anybody I can take her to to get set up optimality??
Many thanks chaps
Also I've got 2 ICV's and I've switched them to see if it makes a difference, as I can't imagine they'd both be knackered, but no difference there

[Duncmasterflex]

Anybody??

[Brianmoooore]

325i ECUs should provide a slightly lean idle mixture without any "setting up". With no lambda sensor connected, the ECU will adopt an appropriate default value.
A M20 TPS doesn't have any 'ohms value' - it's a simple switch for idle, and another one for WOT. The idle switch is either short circuit (zero ohms) or open circuit, and at idle, it must be short circuit.
The only 'adjustment' is the bypass screw for the air meter door, but this is factory set, and should never need moving.
Some BBTB leave very little gasket area between the TB and the inlet manifold. Sure you don't have an air leak there?

[Brdjo]

The only 'adjustment' is the bypass screw for the air meter door, but this is factory set, and should never need moving.

If I'm right, the number is stamped close to the screw, and it's gap in millimeters between top and screw..

[Duncmasterflex]

Ok Bri, well I'll check that, I shouldn't have as I used new gaskets throughout and was super anal with all the torquing down.
I'll check the TPS as per manual, the only possible place there could be an air leak is one of the small elbows off the throttle body, as the chap who did my BBTB lost one of them, and the one he sent me to replace it was too big so I crudely machined it down and pushed it in with some blue hylomar to seal it.

[Carmo13]

Have your injectors been refurbished?
Going by peoples reviews, this usually improves their idle.
Apart from that, poor idles are usually air leak related.

[Duncmasterflex]

Have your injectors been refurbished?
Going by peoples reviews, this usually improves their idle.
Apart from that, poor idles are usually air leak related.

No they haven't mate, but I've got a spare set so I think I'm gonna get them done soon just to see if it makes a difference. Still when she comes on the power she's pulling like a train, even though I'm still running her in and not revving over 3500rpm

[Carmo13]

Knowledgeable people on here say its one of the best things you can do to help tune up a tired engine.
Have a look in the Traders section on here and look for Injectortune. He is a trusted Trader, but can be a little difficult to get hold of some times by the looks of it.

[Yeti]

the TPS should click as you just open the throttle. the car doesn't need to be on. if it doesn't click the car wont go into idle 'mode'.

[Duncmasterflex]

Knowledgeable people on here say its one of the best things you can do to help tune up a tired engine.
Have a look in the Traders section on here and look for Injectortune. He is a trusted Trader, but can be a little difficult to get hold of some times by the looks of it.

Thanks mate, I'll get n the case soon, every little bit helps

[Duncmasterflex]

the TPS should click as you just open the throttle. the car doesn't need to be on. if it doesn't click the car wont go into idle 'mode'.

I'll try this later, I had a look at adjusting the TPS at the weekend, but it looks like I've gotta take the throttle body off to get to one of the adjustment screws so I'll wait until I get it in the garage again, as I've only got limited tools and patience at home! Cheers mate

[Duncmasterflex]

Just an update guys- I took the throttle body off, re-gapped the butterfly, adjusted the TPS to within the parameters in the Bentley manual, and took the slack out of the throttle cable and she's a different car now, idles beautifully
I've also sent my spare set of injectors off to injectortune for refurb, so I'll switch them next week and hopefully I'll see even more improvement.
Thanks for all the help chaps, it's very satisfying to get her running right

[pierce]

Hey Dunc,

Can I ask how you re-gapped the throttle butterfly?

I know that "messing" with this is pretty frowned upon (for good reason)

Im not suggesting you "messed with it" but how exactly did you do it?

I have read some great "how-to's" on the forum, but this is the first thread I've read with a follow up post to say it worked!

Cheers

[Brianmoooore]

Can I ask how you re-gapped the throttle butterfly?

My favoured method is to block the ICV hoses, start the engine, and adjust the stop for an idle speed of around 500 RPM - when the engine begins to shake about on its mounts.

[paultv]

I tried the Bently approach - they suggest that the accurate way to reset the butterfly gap is with a feeler gauge, set to 15 thou. This creates an engine idle speed of around 1800rpm on my car - so that's pretty crap and obviously wrong.

I'd have thought that the idle without the ICV should be around what the ICV creates, so at the point you press the pedal to accelerate, the TPS switches and the opening air intake takes over - surely if the non ICV revs are lower then there will be a point as the TPS changes state when the revs will drop then pick up -

I've noticed that when taking my foot off slowing towards lights and depressing the clutch, the revs drop below normal idle momentarily and then recover as the ICV takes charge -

Anyway, this is all conjecture on my part as I'm not exactly sure how the factory set up should be.

interesting....

Paul

[Brianmoooore]

The ICV can only increase engine revs, not reduce them, so the base idle (on the throttle stop) must be set so that, with no flow through the ICV, the revs are somewhat less than correct idle. The ICV can then partly open to increase the revs to the correct idle.
The correct way to set the throttle stop is to replace the ICV with a special BMW tool, which is effectively a dummy ICV fixed at 'normal' opening, and to then adjust the stop for correct idle revs. No feeler gauges involved.
If you block off the ICV on a normal, correctly adjusted, unmolested engine, then you will find that it idles at around what I said, so my method is a close approximation to the factory method.
The TPS must switch as soon as possible after the throttle moves off of its stop, consistent with reliably switching back again when the throttle is closed.

[paultv]

Makes sense Brian.

If I block the ICV the car won't start unless I open the butterfly more, then I can get it to run at a lumpy 500rpm, so this would need a TPS re adjustment - my jalopy has been well molested.

I'll have a fiddle

Paul