Intermittent high / fast idle?

In article , Lester Burnham scribeth thus

Not at all..

Snipped a tad..

Only thing that -seems- it has much to do with it is elevated temperature. I've got an almost identical problem on the Audisaurus and when it was hot the other day it was almost up to 2000 RPM on idle and would not respond to the quick flick on and off of the ignition switch which clams it down to 800 odd..

I too have a replacement pattern e-bay idle valve and I sometimes wonder if that might be the cause..

I'm minded to clean out the original which was causing stalling and see if thats any different..

It does seem temperature related - and seems to be when the engine has got truly warm from running / driving a while, rather than just showing normal coolant temperature.

Turning off, then on, doesn't seem to help mine.

After a while of using the new one, I did wonder whether there was anything wrong with my original - at least anything other than needing a good clean.

I've not had any repeated instances of blipping the throttle driving the high idle even higher - I sort of attributed that to issues with the IACV.

I suspect you're right about where the problem is. The only thing I was thinking about, software wise, was that it may give me some clues as to what's going on when it does this.

The past couple of instances, there's not been the time to unplug the IACV, either I've been driving in places difficult to stop, and / or the revs have gone up to high, I was more worried about driving them down somehow.

As I mentioned in my reply to Tony, I think there might have been a minor problem with the IACV at one point - the blipping of the throttle when the idle was high, driving it even higher - which now doesn't happen.

In terms of an air leak, is spraying carb cleaner around vacuum lines a reasonably safe approach?

I personally avoid using carby cleaner around the lines so its not ingested causing other problems - its a savage solvent.

Oil is a good substitute or WD40.

Diagnostic software can only help where it has the data to diagnose. The ICV, for example, doesn't supply any such data.

FPWM.

This car's ECU can at least detect when it's disconnected, though - whether that's purely electrical (don't think so based on the symptoms) or perhaps affect on long term idle trim - with the IACV disconnected, the check engine light came on after 2 cycles of the engine running - reverse for plugging it back in.

Previously cars, where I've had to tinker, and at times unplug, the IACV, and there's been no warning lights.

I think where I'm coming from with the diagnostic software, is it seems to have a dashboard showing a fair few parameters - I was just hoping when it exhibits the behaviour, something looks different (not necessarily fault code producing, mind) to normal - and I think it allows some logging as well as real-time display.

From where I'm sat, the idle going up can only be a few things, really: sticking throttle / cable - should be physically visible, under the bonnet, and wouldn't account for the idle now slowly, but steadily increasing; IACV doing it - either because it's faulty, or because the ECU is telling it to; fuelling being increased for some reason (iffy TPS, or CTS) - but would have thought there should be error codes for that; induction leak - again would have thought there should be error codes for that.

Given the lack of error codes, one thing that's been haunting me about this, is somebody posting to a forum about the idle speed on a Mini (I assume the current one, not the original one), and it being raised because the ECU was seeing some issue with the alternator's output, and increasing idle to compensate. In that scenario, would you either expect there to be fault codes stored, or some other warning lights (battery?). I keep coming back to think about this, because I'm wondering whether there would be any other obvious symptoms, or software / codes evidence.

Yeabut how would the ECU know what -load- was on the alternator?..

Err umm .. Firmware upgrade;-!...

It wouldn't need to:

Engine running? System voltage low? Up the idle rpm a bit until voltage is OK.

Chris

Exactly - that's what I'm wondering about. And I do wonder whether anything would get flagged as an error.

Would account for the symptoms - increasing idle, as the increased idle seems to have got worse.

What I'm not sure about - because, largely, car electrics are still a bit of a mystery to me - is whether heat - perhaps especially high under-bonnet heat - could be a factor influencing how much the alternator was playing up.

I'm also wondering whether the OBD dongle and software, might at least give me some indications, reporting stuff in real-time, both when the engine is behaving normally, and when playing up.

Further update - perhaps some progress...

I got a chance to plug in my newly acquired USB thingmy (ELM interface - £13.95 from ebay, with some software - easyobd, I think it's called). Have to say, it's been worth every penny.

So I took my laptop and interface out to the car, connected it all up started the car. Idle was perhaps normal for cold, but didn't seem to drop, in fact slowly rose and started to race at 3k and climbing.

I had the software connected, and could see quite a lot of parameters, and inspect the output / readings of quite a few sensors. The coolant and air temperature readings all seemed very plausible and valid (coolant temp raising as you'd expect). Wasn't sure what to expect with some of the other sensors (02 for example, and there was 2 readings - the first showed an indication of running rich / lean - as did another reading on fuel trim).

There was readings for engine load (calculated), battery volts (presumably however the ECU measures that) and "Absolute Throttle Position".

When it was playing up - ie revs climbing and racing - nothing looked unusual, other than the revs - coolant temperature was rising as you'd expect. "Battery volts" didn't show any particularl change (on all readings and logs, seems to be somewhere between 13.9v and around 14.2v).

The one thing that struck me as slightly odd, from the very off (ie engine start at truly cold - not been started for about 3 days) was that the "Absolute Throttle Position" was ranging from somewhere above 7.0% to

Blipping the throttle, at this point, just pushed the revs higher. So I disconnected the IACV. Absolute Throttle Position value went to 0%, and then there was a code pending - no active code, mind, nor any MIL.

Monitored it like that for a while, and it largely behaved like it had done in other instances of disconnecting the IACV (ie just electrically by removing the plug). Looking at other measurements, the engine ran richer at this point (ie with the IACV unplugged).

After a bit, I wondered what would happen if I plugged it in again - would the engine start to race, or would it just settle. So I did - idle dropped to somewhere in the normal region (a little over 900). And stayed like that. And Absolute Throttle Position remained at 0%. Engine behaved perfectly, even in response to blipping the throttle.

Thinking that I'd only termporarily "tricked" the ECU into thinking everything was OK, I saved the current log of readings. And turned of the car. I started it again, switched on the software to watch all the parameters (it would be pretty much well warm by this point), again idle in normal(ish) range (a little over 900 - I perhaps would have expected around the 850 mark, but 900 and a bit is considerably more normal than 1500 rising to 2k and beyond), absolute throttle position still 0%, calculated engine load perhaps lower than previously.

Not wanting this to be a fluke, I saved the current log of readings, then turned off. Gave it a few seconds, then turned it on again, and started monitoring - exactly the same - pretty normal idling (low 900s), absolute throttle position still 0% and unchanging unless I moved the throttle pedal, everything looking normal, no problems, no pending codes, everything looked (as far as I could see) normal.

A few hours later, I drove the car for a fair while, some local movements, then a reasonable run of around 30 minutes. Everything seemed to behave as normal - no high idle, no issues at all that I could see. After being parked up for a couple of hours, made a return journey of about 30 minutes - same again, everything seemed normal and fine.

So concluding from that, I could only think that some learning of the idle was needed by the ECU (after all, I'd reset it a few times by either removing the ECU fuse, or by doing so with my code reader) which makes me wonder, could it possibly be a required step to plug in the IACV (or a new one) after letting the car idle a bit, and then idle trim is established?

That's how it looked from monitoring it, and it's behaviour for the rest of the day. Any comments or feedback on that theory welcome - either way.

Problem is, that sounds a little strange to me, and I've had instances where I thought it had all gone away / been fixed, only for it to return with a vengance some days later.

Still, at least I have something of a trick that seems to keep it running fine for a while, if it happens again.

Thanks for your patience, if you're still reading this!

You can't get an indication of anything other than the correct mixture with the engine hot. That's all a narrow band lambda sensor can tell you. And the mixture will be rich while the engine is warming up.

Well there was 2 different metrics - one of them was "Short Term Fuel Trim Bank 1" which seemed to flip / flip between being lean and rich most of the time - 'cept when the IACV was disconnected, then it seemed to show consistently rich (the first O2 sensor seemed to largely be congruent with this reading, too). When it was plugged back in again, it went back to being largely lean, with the occasional flip / flop to rich.

I don't know how accurate the gizmo and / or software is, but it was just a curious thing, really, unplugging the IACV definitely seemed to have a bearing on it running rich. That said, other than being something to note of interest, I don't think that particular finding adds much to either the problem diagnosis, or resolution of it - but as it related to the IACV being (electically and physically) present, I wasn't sure if it had any bearing.

Well measuring the volts might not be the most accurate method to determine the load on the alternator the amps would be the way to go but either way I somehow have doubts this is causing the problem concerned;!.,..

Its quite possible that you might have a duff joint somewhere around that un plugging and re plugging the IACV lead may well be disturbing which will be OK for a day or two or three or more. Such is the way of modern electric's..

I have read about this ECU learning but it seems that the ECU might be learning the wrong things..

Anyways I expect that a garage doing the same job might be finding this just as awkward to fix except that its often very useful to have spares around to swap out just in case you might have a duff new one, and I've seen that in other applications more than the once;!...

Keep us all informed of progress!...

As I said, the system wouldn't *need* to know the "load" on the alternator; it just wants to know that the battery is not discharging. Pretty much all ECU's get voltage feedback anyway, so it's a trivial bit of software to give added security.

Providing a feedback to the ECU giving the current in the charging system would be expensive and pointless.

I also doubt that it's anything to do with the OP's problems, especially as it's unclear as to whether has car has such a system.

Chris

Given every ECU is connected to the car electrical system, it's fair to say it will know the voltage. ;-)

Most ECUs will alter the injector opening time to compensate for a varying

As IMHO is having the ECU control the alternator. It's quite capable of doing so itself. As they have been doing since first introduced.

The fact that it is supplied by the car's system doesn't automatically mean that it will "know" the voltage in the sense of being able to detect what the actual voltage is.

Indeed. By virtue of the trivial piece of s/w I mentioned.

Are you saying that systems that have better control of battery charge by using the ECU are not a good thing? If so, I'm afraid I disagree strongly.

Systems like Ford's Smart Charge have significantly improved battery life, and likewise reduced the chances of being stranded with a flat battery. Again, there is very little cost. Existing sensors are used for things like temperature monitoring. There is one extra wire to the alternator. The rest is done in software.

The actual regulation is still done in the alternator; you can remove the single extra wire to the alternator and it will still charge.

What's not to like ;-)

Chris

Pointless. Except to tie you into Ford spare parts.

The batteries on both my cars are over 7 years old. The one on the SD1 -= which sometimes isn't used - has gone flat a few times too. It's a no name far east one from the local accessory shop. The BMW one Bosch.

And as we all know software means perfect? ;-)

All rather OTT for a simple lead acid battery.

How does it do that? Many non-OEM alternators are available for my Focus...

The battery on my last Focus was 10 years old, and still starting the car in all conditions.

Absolutely not. Smart Charge is one of Ford's better ideas.

Chris