Another idle control thread!

[Neil_uk7]

So I'm still trying to solve this problem: [325i 1988]

Car seems to idle ok at around 700rpm. But as soon as I raise the revs, the next stop is 1500rpm. I can't hit anything in between the two.

I've tried the following:
- cleaned the throttle butterfly
- replaced the AFM and ICV
- new crankcase breather hose
- checked blue temp sensor - all ok
- fuel injectors cleaned professionally
- new fuel filter
- cleaned TPS with carb cleaner and taken Brianmooores advice drilling the bottom to release any gunk (there wasn't any)
- test TPS (ok) and set up correctly so clicks at throttle stop
- new throttle housing and AFM gasket
- new air filter
- checked for air leaks (visually and using carb cleaner)
- checked rocker cover is tight and no air leaks

What am I missing? Someone in one of my previous threads suggested valve clearances which I'm not competent enough to do. But is this likely to cause the problem I've described? I'm really struggling here and my next thoughts are:

- replace HT leads
- replace blue temp sensor (even though it tests fine)
- replace air intake boot (even though it doesn't leak)
- use the car as a boat anchor

[Martinaston]

Quote"- test TPS (ok) and set up correctly so clicks at throttle stop "

Clarify that please

[Neil_uk7]

The TPS shows continuity at throttle stop and variable resistance after that up until WOT where if I remember correctly it shows open circuit a few degrees before completely open throttle. I used an article of the pelican thread to check it.

I forgot to mention I've replaced the spark plugs, and checked the C101 and C192 plugs and their all ok. If I disconnect the idle control valve electrical plug the problem all but disappears hence I replaced this thinking it was the problem but it's still there.

[Martinaston]

Is it an auto ?

[aeberbach]

"valve clearances which I'm not competent enough to do"

You did all the rest, you can do clearances too. Really! Get a good guide, follow it carefully, no problem. You don't even need special tools and you probably already have a set of feelers if you gapped your plugs.

Pelican article:
http://www.pelicanparts.com/bmw/techart ... Adjust.htm

In my opinion the article makes the eccentric adjustment look harder than it is. Once you see it in front of you it's obvious. You don't need the BMW adjuster tool just any metal rod fine enough to fit in the hole. I think a 3mm allen key works?

Your TPS operation sounds right. One thing I would check is the electrical measurement at the ECU connector, verifying that the connection is OK all the way to the ECU, not just at the pins of the idle control valve itself. I discovered a connector issue on my car this way although the ICV itself was fine. What does the car do if you pull the ICV plug off while it is idling - anything? If your ICV is working idle will change.

On the idle speed issue - has anyone messed with the air bypass screw maybe (right side of the throttle body) and adjusted the mixture without the benefit of a gas analyser?

[Neil_uk7]

One thing I would check is the electrical measurement at the ECU connector, verifying that the connection is OK all the way to the ECU, not just at the pins of the idle control valve itself.

This is one thing I haven't tried - everything else electrically seems in good order so I doubt I'll find fault here but will certainly check.

If you pull the ICV plug off when it's idling, nothing happens except when it comes off idle stop it revs smoothly upwards from about 900rpm and the lost rev range is all but restored. So basically I can fix this problem by unplugging the ICV!

Unfortunately yes someone has messed with both the throttle stop and AFM so I've set the butterfly as best as possible leaving a 0.015 gap I believe between the plate and the housing. The AFM screw however is wound all of the way in. Winding it out to make the mixture leaner doesn't really help matters.

No it's not an auto Martinason

[Martinaston]

Then you should not be getting an increasing resistance at the TPS.
Auto is a 4 or 5 pin round plug TPS.
Manual is a 3 pin flat plug TPS.

With the manual 3 pin TPS you should get continuity at one of the pins when the throttle is closed.
Continuity at the other pin when the throttle is wide open.
(Can't remember which way round the pins are)

The "click" should occur just as the throttle starts to open by a gnats chuff, that breaks the continuity (circuit) of the first pin and turns off the ICV.

[e301988325i]

leaving a 0.015 gap I believe between the plate and the housing. The AFM screw however is wound all of the way in. Winding it out to make the mixture leaner doesn't really help matters.

No it's not an auto Martinason

Have you had the idle co2 set on a garages gas analyser yet? Describe how you've set the 0.015 (inches?) TB gap?

[aeberbach]

"The AFM screw however is wound all of the way in"

Oily black spark plugs? Step 1 is to take it to a friendly garage and get the tuning that requires a gas analyser done, I'm going to do this myself once I get the head back on and can drive it again.

(mine is an auto but has the three pin ICV connector)

[Neil_uk7]

Ok to answer a few responses
Martinaston:

Then you should not be getting an increasing resistance at the TPS.

Yes it is a manual - I tested my TPS according to these instructions and it tested ok

With the throttle closed there should be continuity between the inner and one of the outer pins
With the throttle partially open there should be no continuity between any of the pins
With the throttle fully open (about 7 degrees from it’s end) there should be continuity between the inner and the other of the outer pins

As a quick check if at least the idle switch is working you could disconnect the connector with the car idling. The idle speed should rise when you do this.

e301988325i

Have you had the idle co2 set on a garages gas analyser yet? Describe how you've set the 0.015 (inches?)

The co2 has not been set on a gas analyser and could for all I know be all over the place although it did go through the MOT a couple of weeks back. I used a set of feeler gauges between the throttle body housing and butterfly to set the TB gap.

aeberbach:

Oily black spark plugs?

Nope - had new plugs a few months back. One of the originals was oily but only because it had no gap!

Thanks zoners for the ideas but I can't help feeling something is definitely faulty. Even if the mixture is out, I doubt the car would rev freely and perfectly from 1500rpm up to red line with no issues. There is a little hesitation when I first put my foot on the throttle but other than that - a ok.

[e301988325i]

If the butterfly is being held open 0.015" or 0.4mm from the housing then this is your problem, it's letting too much air through. Set it with a bit of normal A4 paper, so that you can move the paper freely pushing and pulling, then reset the TPS.

Then get the idle co2 set, the car is supposed to run at 1%, 3% is the MOT limit, potentialy quite a difference!

[Neil_uk7]

Will check and adjust the butterfly again today, but I have previuosly tried setting the butterfly using the A4 paper method but no luck. I did wonder if the TPS was at fault but it's just a switch right? It works or is doesn't. Is there any chance dodgy HT leads could be causing this problem? And how would I test my HT leads?

[clipper]

I've posted this before and been crticised for suggesting that people should mess with it but to me it seems very unlikely that a properly set up and running engine would have the AFM screw wound right in.

Mine was set like this (seemingly to try to mask the effects of an air leak). Once the engine was "good" I had the CO2 set at my local garage (they told me that they had wound the screw back out a long way) and all is still good.

If you haven't yet had it set up properly I can't see what harm you could do by winding the screw ot a few turns to see what happens. At least you know how it is now and can easily put it back if it doesn't help.

[Neil_uk7]

THanks for the suggestion clipper - been there done that! In fact I'm running out of ideas to try. When I backed off the AFM to make the mixture leaner, the car began to run lumpy. I agree that a properly setup system probably should not have the AFM mixture screw wound all the way in but until I can find the problem which is being masked it's the only way the car will run.

[clipper]

Well going by that the car doesn't appear to run overly rich at tick-over with the AFM screw wound right in, it would seem likely that air is getting in somewhere too. I know you say you've checked for leaks but something's wrong somewhere.

What happens if you take off the oil filler cap when idling ?

[Neil_uk7]

Oil filler cap off when idling and the revs drop - as I would expect.

When I acquired the car, it was ticking over at around 1400rpm at idle. The previous owner (or someone) had wound the throttle stop in so the TPS was doing nothing (well it never reached idle map). Once I removed the TPS and cleaned it out, I could then reset it to click at idle. But ever since then I've had problems. I've tested the TPS again today and sure enough, continuity at throttle closed, throttle wide open and nothing in between - text book.

Now out for a burn and to fiddle with a few things see what I can learn.

[e301988325i]

Will check and adjust the butterfly again today, but I have previuosly tried setting the butterfly using the A4 paper method but no luck. I did wonder if the TPS was at fault but it's just a switch right? It works or is doesn't. Is there any chance dodgy HT leads could be causing this problem? And how would I test my HT leads?

I've had the exact same problem nothing between idle and 1250rpm, my TB was open too far, closed it a bit problem inproved, my BBTB doesn't help. TPS is just a very simple switch, but checking it's function at the ECU socket pins is the real test if persistent problems occur.

HT leads are not causing this, any problems they cause would be apparant at all revs, they are incredibly durable, unless they are pulled on by a muppet to remove the spark plug caps. Their resistance can be measured and checked against a known value 5 or 6k ohms IIRC do a search for it.

[Martinaston]

You keep saying the TPS clicks at idle, its not the click when the throttle closes thats important.
Its the click as the throttle opens.
It HAS to be set to switch off the ICV as the throttle starts to move by a fraction of a degree.
If its set too far away then you get a flat spot.

Its best done with the throttle body off the manifold. the throttle stop screw should be set so you can just see some light through the edge of the butterfly. Don't bother jamming bits of paper or feeler guages in there. The idea is to stop the butterfly jamming when the two bits of metal expand at different rates as the engine warms up.
Once thats done then set the TPS.

[e301988325i]

You keep saying the TPS clicks at idle, its not the click when the throttle closes thats important.
Its the click as the throttle opens.
It HAS to be set to switch off the ICV as the throttle starts to move by a fraction of a degree.
If its set too far away then you get a flat spot.

Its best done with the throttle body off the manifold. the throttle stop screw should be set so you can just see some light through the edge of the butterfly. Don't bother jamming bits of paper or feeler guages in there. The idea is to stop the butterfly jamming when the two bits of metal expand at different rates as the engine warms up.
Once thats done then set the TPS.

I agree with what you say about the TPS, but the throttle was set slightly open at the factory using a special tool to place the ICV in the middle of it's operating range.

[Martinaston]

That will have to be best guess then, unless you know how they did it ?

[e301988325i]

This is Brian.M's knowledge regurgitated; He doesn't know the diameter of said tool either.

They fitted a fixed diameter tool in place of the ICV which replicated the middle of the ICV's range, then adjusted the throttle stop (and AFM I guess) to get the revs and mixture correct, then replaced the tool with ICV.

Doesn't make sense to me, why not just electrically set the ICV to mid postion, anyway that's neither here nor there?

[The_Diddler]

I have a very similar problem with my b25 engine.

Starting from cold, car very lumpy, couldnt rev it, it would cut out, this went away when warm, however when driving all seems fine under power, when cruising at a constant speed car again seemed lumpy and hesitant.

Swopped over blue sensor first of all, car was already warm, first difference i noticed was when cruising all the lumpyness had disapeared it became nice and smooth when at a constant speed.

Left car for a couple of days, started again and the same problems when cold arised, very lumpy and wouldnt rev until warmed up.

I was going to try the TPS next, how exactly do you set it up properly, what do you need to do.

If OP wants i can start another thread if required

[Martinaston]

This is Brian.M's knowledge regurgitated; He doesn't know the diameter of said tool either.

They fitted a fixed diameter tool in place of the ICV which replicated the middle of the ICV's range, then adjusted the throttle stop (and AFM I guess) to get the revs and mixture correct, then replaced the tool with ICV.

Doesn't make sense to me, why not just electrically set the ICV to mid postion, anyway that's neither here nor there?

ICV was probably nowhere in sight, Probably done on a bench with just the throttle body and an air/vacuum pump.

[Neil_uk7]

e301988325i:

my BBTB doesn't help

Sorry but I'm still a noob and feeling my way a bit. Whats a BBTB and do you know which pins I need to test at the ECU?

In reference to your comment concerning HT leads, I did notice today that it seems a little hesitant across the rev range under acceleration unless you really boot the throttle. Not sure if this has any bearing on the condition of the leads but will do a search for the resistance measurement and test them tomorrow (hopefully they're duff and the problem will be sorted)!

Martinaston:

Its the click as the throttle opens. It HAS to be set to switch off the ICV as the throttle starts to move by a fraction of a degree. If its set too far away then you get a flat spot.

After resetting it all again today it does exactly what you describe it should.

...should be set so you can just see some light through the edge of the butterfly.

Like this?


e301988325i:

They fitted a fixed diameter tool in place of the ICV which replicated the middle of the ICV's range...

I've read somewhere that a hole drilled with a 1/8 drill bit can replicate the tool (roughly) but this still yielded no joy.

Thanks The_Diddler for your input to the thread - I'm happy to continue with this one and see if we can kill two birds with one stone. I haven't replaced my blue temp sensor as it tested according to measurements I read of here:

http://www.rickk.net/i/drive/bmw-e30-32 ... nformation

This may also help you set up your TPS etc.

[Martinaston]

Yeah thats pretty much all you can do with it.
I noticed you said you changed the ICV, have you cleaned it with a carb cleaner spray ?
It may be just as lazy as the original.

[staley_turbo]

Have you checked timing? and crank sensor? just some other thoughts..

[Neil_uk7]

Not checked the timing - don't have the equipment. Where's the crank sensor? What should it read? (resistance/voltage?)

[staley_turbo]

You dont realy need any equipment. Just check the timing marks.

And check for dirt or anything bent on crank sensor. Should be on the front of the engine above the pickup ring near the aux belts.

[e301988325i]

my BBTB doesn't help

Sorry but I'm still a noob and feeling my way a bit. Whats a BBTB and do you know which pins I need to test at the ECU?

Big Bore Throttle Body

In reference to your comment concerning HT leads, I did notice today that it seems a little hesitant across the rev range under acceleration unless you really boot the throttle. Not sure if this has any bearing on the condition of the leads but will do a search for the resistance measurement and test them tomorrow (hopefully they're duff and the problem will be sorted)!

It's not completely unheard of, plenty of 2nd hand sets available, BMW parts only I'm afraid. New = £120

Its the click as the throttle opens. It HAS to be set to switch off the ICV as the throttle starts to move by a fraction of a degree. If its set too far away then you get a flat spot.

After resetting it all again today it does exactly what you describe it should.

...should be set so you can just see some light through the edge of the butterfly.

Like this?


That to me looks a little bit too open, but it's hard to tell TBH, what's the gap?

They fitted a fixed diameter tool in place of the ICV which replicated the middle of the ICV's range...

I've read somewhere that a hole drilled with a 1/8 drill bit can replicate the tool (roughly) but this still yielded no joy. [/quote] Have you tried this? You havn't set the mixture, or tappets so I wouldn't dismiss it yet.

[Neil_uk7]

e301988325i:

That to me looks a little bit too open, but it's hard to tell TBH, what's the gap?

The width of one side of a torn envelope! The throttle stop could be wound in another 1/4 turn and I'll try this but much more and it'll be closed. Doubt there'll be much difference - after all I'm missing about 700rpm or more.

I've tried the hole in the penny trick but no luck.

The throttle does feel much more responsive with the AFM screw wound all the way in. Will try testing the leads this weekend before I go further. Getting very demoralised now ...

[e301988325i]

The AFM mixture screw will only really have any effect at idle and very small throttle openings, which is what your having problems with. . . I don't know which pins on the ECU socket, search may bring up an ECU socket diagram, the 3 rows of pins are only numbered at one end, so you have to start counting which is a trifle fiddly!

[Neil_uk7]

So a bit of an update - I've checked the s/history and the cambelt was changed only a few thousand miles back so I'm going to assume the timing is good.

e301988325i:

I don't know which pins on the ECU socket, search may bring up an ECU socket diagram

Not yet found an ECU diagram to test the TPS at the ECU but hopefully will this weekend.

I've backed off the throttle stop 1/4 turn - any further and it'll be closed tight; still no difference.

HT lead test has resulted in the following:

6.06K/ohms
5.58K/ohms
5.50K/ohms
5.51K/ohms
5.83K/ohms
5.75K/ohms

Coil lead tested bang on 2K/ohms. Now in a different thread elsewhere willnz tells me they should be 6K and the coil no more than 1.2K. Have I found my fault? Willnz - if your watching?