E30 Zone

i have a 320i, had it 6 months and i've got a bit of a flat spot on accelaration. top end is fine, idle is a pip rough, but not really. i've changed plugs, put fuel line cleaner in, new air filter (K&N). someone told me about the idle air stabliser valve. i got me a haynes manual and it says that if you disconnect the electrical connector, the revs should go up to 2000. and if they don't, you are to do some checks. first on the unit to test resistance across the terminals and i pass, then with the voltage coming into the unit, and i pass that too. so these test tell me the unit is fine, however when i disconnect it the revs stay the same. i think it is sticking closed, i opened it fully with a screw driver and DID NOT hook up the electrics, basically bypassing the valve and when i start up the revs jump from 1500 to 2000, like you are sitting there constantly rev rev rev revving. i gave her a little spin in this condition and sure enough the flat spot was not there, however the revs obviously didnt go below 1500, when i hoooked up the electrics again and sort of played with the throttle to keep it above 1500 and i had no flat spot anyway, my flat spot is right at the bottom of the revs. if i floor it it hesitates for about 1 second then kicks in and rips off.
anybody got any ideas. and thank you if you take the time to read this and reply.

I'd be interested in reading the replies to this too...

Giles.

confusion wrote:my flat spot is right at the bottom of the revs. if i floor it it hesitates for about 1 second then kicks in and rips off.
anybody got any ideas. and thank you if you take the time to read this and reply.

That's a characteristic of the mechanical AFM, you'll find most E30's with an AFM behave in this manner.

Just been out to check mine. Disconnected the ICV contact, started the car and there was no change from normal... idling at just under 900rpm.

Connected it back up, no change. Disconnected it again, no change.

From this, I think that must mean the ICV needs a good clean. Will do it tonight and let you know the outcome...

Giles.

Geeman wrote:Just been out to check mine. Disconnected the ICV contact, started the car and there was no change from normal... idling at just under 900rpm.

Connected it back up, no change. Disconnected it again, no change.

From this, I think that must mean the ICV needs a good clean. Will do it tonight and let you know the outcome...

Giles.

I've found that some ICV's respond to unplugging and plugging in but some just stay the same even if you clean them.

It's strange because if I remove the oil cap from my rocker cover, there's no change but on other car's if you remove them, it runs really lumpy.

removing my oil cap also has no effect, but really affects my iS

Karan wrote:removing my oil cap also has no effect, but really affects my iS

Well we do have more cylinders to keep them running

E30Adam Wrote

I've found that some ICV's respond to unplugging and plugging in but some just stay the same even if you clean them.

Thats exactly what I found.

So I've just ordered a new one - Did I do right???

Tris

SVBMW wrote:E30Adam Wrote

I've found that some ICV's respond to unplugging and plugging in but some just stay the same even if you clean them.

Thats exactly what I found.

So I've just ordered a new one - Did I do right???

Tris

Well... the ones that were perfectly clen that didn't respond to unplugging I've found to be okay, mine doesn't change it you unplug it and the car runs fine.

Spoken to PacerPete about this... he reckons there definitely should be a change in revs if you unplug them. If not, there's something wrong.

When you take the ICV off, shake it. If you can hear rattlings inside, it's okay, if not then it needs checking/cleaning/replacing...

Will be doing mine tonight...

Giles.

I used to have this problem on my 320i.

When you went to pull out of a junction you'd have to be careful to hit the revs a bit before to let it drop then pick up so you could pull away and not stall.

I tried many different ICV's, none made any difference. Tried a different AFM, didn't help.

I tried the ECU out of my 325i breaker, and this cured it. After a short while with it fitted, it revved quickly. Still gave good fuel economy too, on a run.

I would find a replacement 320i ECU, but I'm putting the 325 engine in soon, so I won't bother.

But this is just to let you know it 'could' be an ECU fault. Nothing else helped.

Pacerpete had a fiddle, so did others, to no real conclusion or solution.

Until I swapped the ECU. Runs SO much better now.

So you've got a 325 ECU. Has it got the 325 chip, or the 320 chip in it...?

It's still got the 2.5 chip.

thanks to everyone for replying.
is the ECU that little jobby under the dash by my right knee? and are you saying i could go to the breakers and get me one of them and just swap them straight out, no worrys??
cheers.

dave, when u say changed the ecu, dԚ´you mean the moronic unit with one from a 2.5? or is there a curcuit board that is to be changed,

i have the same semi stutter at lights, which is easily remedyed by holding the rev at 1k and sofly out on the clutch.....this works especially when i start my drives for about 10 mins til shes warmed, then shes much more forgiving

Guys, I'm not saying this is definately what cured it, as I was cleaning out various bits and bobs at the same time. But it was the only thing which seemed to have an effect.

I changed the complete ecu, just unbolted it from above your right knee, as mentioned, pull out the plug and swap it over.

I'm also running a 2.5 AFM. Don't know if this helps/hinders or makes any difference at all!

Johnono, sounds like exactly the problem I had, it's fine now though.

sorry about the ignorance, but what is a 2.5 AFM, also, does the year of the car matter with the ECU. i know there is a 2.5 in a yard near me that is a recent addition, still has the ECU, but it is a good few years earlier than mine. do you think that will make much of a difference?
cheers.

how about a replacement afm, if the old oneԚ´s scored up mabey this could be an option

Re: Engine speed increasing when ICV unplugged.
I might be talking utter rubbish, since I've never had any reason to try this test, but IIRC early ICVs were two wire and later ones three wire.
The two wire version must be a motor applying variable torque against a spring, so if it is unplugged, it will default either to fully open or fully closed, depending on design. The three wire version uses two magnetic fields at right angles to each other, and moves the insides of the valve by balancing one against the other, so when it is unplugged it will stay where ever it happened to be.

oohh brianmoooore good answer dood. i think thats definitely why some do and some don't.

There must me something in the ECU which controls the idle speed in conjunction with the TPS and IACV.
I've just fitted a bigger bore throttle body and the engine would not idle when warm, kept stalling.
Checked voltage from loom plug to IACV and this was out.
Changed the ECU and it cured it. Car idles now when warm.
Does anybody know if the unit which controls the idle within the ECU can be transferred to my old ECU, as i have a Bexley chip in i think but this has got me wondering as i went for a spin with a standard ECU connected and i couldn't tell the difference.