Idling AGAIN...would like to sort this once and for all!

[MrDazzle]

Hi,

I've been searching around the zone for the past few weeks in an attempt to sort my idle...could I please have some suggestions.

Situation is this: The car used to idle just fine. Then I had an unexplained loss of oil pressure so I bought a 'new' engine from another zoner. Since then it hasn't idled smoothly (about 5 months).

First off it was all over the place and eventually refused to idle at all. That turned out to be because I hadn't reconnected the alernator!

After that, it was still hunting and dropping to the point of stalling. I (foolishly I now know) turned up the idle speed using the 'adjuster screw' (I know, I know....). That sorted the problem merely by making the car idle at 1000rpm.

I then changed the blue temp sensor just 'cause I had one spare. I then changed the ECU back to stock on the advice of work collegues. Neither of those things cured the idle, although the car drives better on the stock ECU.

I've now fitted a new ICV and now the car idles at a constant 750rpm but it 'chugs' alot and doesn't run smoothly. If you rev, or when you come to a stop the idle speed momentarily drops below 750rpm then picks up again. Sometimes it stalls.

I've investigated the TPS. First off I tried the engine without it connected, and the idle rose to about 3000rpm. There's continuity between pins 1 and 2 when the throttle is closed, and between 2 and 3 when you open it.

As far as I can see the hoses are all fine.

I've also put some new plugs in...the old ones have light grey, almost white powdery deposits on them. That would suggest the car is running a bit lean?

What should I try now. I'm guessing the fact the 'idle stop' has been moved means I'm a bit shafted?

What does that screw do anyway? I've been talking to people at work (I'm a calibration engineer for an engine design consultancy) and they can't see why moving it should be a disaster?

Any suggestions?:)

[SPADGE]

Could well be the AFM or mixture.
Take it to an m.o.t station or garage and get them to check the mixture mate

[MrDazzle]

Forgot to mention that...

Had an MOT last weekend. CO was 0.69%, Hydrocarbons were 475ppm. That passed, but I dunno if it's indicative of a problem?

[SPADGE]

Forgot to mention that...

Had an MOT last weekend. CO was 0.69%, Hydrocarbons were 475ppm. That passed, but I dunno if it's indicative of a problem?

CO looks way too low to me mate!
I'll wager that if it was richened your idle will improve.

[MrDazzle]

KK.

I heard something about adjusting/fiddling the AFM. Apparently there's an electrical contact the wears and you can adjust the track?

Is that true?

Should probably take it to get set-up with EGA etc really. Could probably do it at work actually. Is there a simple mixture adjustment?

[SPADGE]

KK.

I heard something about adjusting/fiddling the AFM. Apparently there's an electrical contact the wears and you can adjust the track?

Is that true?

Should probably take it to get set-up with EGA etc really. Could probably do it at work actually. Is there a simple mixture adjustment?

There is an adjustment screw on the top of the afm mate
You need an allen key to do it.
It needs hooking up to a gas anylser to do it.

[MrDazzle]

Yeah I thought that would be the case.

I just thought there was also a relatively simple fix for a slightly dodgy AFM, something to do with poor/dirty contacts inside.

[SPADGE]

Yeah I thought that would be the case.

I just thought there was also a relatively simple fix for a slightly dodgy AFM, something to do with poor/dirty contacts inside.

Cleaning out the afm can often help and would probably be a better bet than making adjustments at this stage. But i would get it hooked up and checked as soon as poss afterwards

[Bobbydoughnut]

MrD, firstly check that you have a constant resitnace curve across the contacts on the AFM with the ignition on and opening the flap gradually with your finger, there shoiuld be no sudden drops while opening. This will tell you if the contacts are worn at all.
There is a recon fix for the AFM, but needs to be handled with real care! You need to take the black sealed top off the AFM body to get access to the ceramic track/spindle/contacts inside, it's not an easy fix but can be done, it's all about moving the contact mount where it locks onto the spindle - move it south on the spindle, that then pushes the contacts north on the track, you'll see 2 the black wear marks in a crescent on the ceramic surface, open the flap inside and you'll see it curve round and moving the contact mount moves it onto a clean part of the track, but it only needs to be moved a mm or so and not twisted at all as this will alter the spring calibration and it's buggered. Be very careful when doing this as the air temp sensor is in there too. I think I have a tutorial for the Porshce 944 AFM recon/fix and it's almost exactly the same BOSCH unit as on the E30 if you need it I'll search for it

[MrDazzle]

Will do the check first.

This is the sort of thing digital multimeters are crap at! It's so much easier to see a smooth change with an analogue dial...

[Bobbydoughnut]

Yup 4 sure, though I still use a old multimeter that I 'borrowed' from college years ago.
You'll get an analogue meter on Fleabay for a couple of quid if easier