flak monkey
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| posted on 19/5/10 at 05:24 PM |
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Weird idle problem
Took the car down to Atspeed in Essex on monday and now runs like a dream other than a minor idling problem which is a little irritating! This is by
no means their fault, I was well aware of it when I left and I knew it was something I was going to have to play around with.
Been playing around with the cold start tonight as we couldnt do this on the dyno. Seems to start and run fine when cold, didnt need much adjustment.
Will continue to play around tomorrow.
I cannot get it to idle properly when hot though. If you leave it idling for any length of time it will go from being too rich (12afr) to too lean
(18-20afr). If you keep it running and dont adjust anything it goes between the 2 about every 2 mins or so. When running rich it idles nice and smooth
+/-50rpm from target with no spark correction. Once it goes lean however it runs too slow, lumpy, misses and whacks in loads of spark correction as
you would expect from running so slow. After a while it usually stalls and then is a pig to restart as it continues to run lean once restarted.
I tried opening the throttle a little with the stop and then bringing the speed back down with ignition and it didnt seem to help. Also tried closing
it a little, and again it didnt help.
I had a hunt around all the corrections and didnt find anything which could affect it. Basically air temp and coolant temp corrections are all zero
when it plays up.
Any suggestions would be greatly appreciated! I have also been in touch with Colin at Atspeed and Andy at Omex. Colin saw the same problems on the
dyno on monday.
Any ideas?
Sera
http://www.motosera.com
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maartenromijn
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| posted on 19/5/10 at 05:35 PM |
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What engine do you have?
This might help you out: http://www.btinternet.com/~madmole/Reference/Idle.html
BLOG: http://thunderroad-super7.blogspot.com/
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flak monkey
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| posted on 19/5/10 at 05:46 PM |
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Its a duratec
The one thin that has made me think from that link is the crankcase breather...
Its not attached to anything at the moment and I wonder if there is a valve in there somewhere....
Off to have a look if I can get to it!
Sera
http://www.motosera.com
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flak monkey
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| posted on 19/5/10 at 06:48 PM |
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Well, and I say this cautiously, that seems to have helped.
What I thought was just an elbow in the breather was actually a PCV. Removed its internals now so it can breathe properly.
So its been running all this time with no crankcase ventilation. Oops!
It does seem to have helped and hopefully now I can get my idle tuned up properly when its cooled down again tomorrow (everything gettin rather
warm)
Thanks for the inspiration!
Sera
http://www.motosera.com
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MikeRJ
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| posted on 19/5/10 at 07:16 PM |
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Another thing to beware of is electric cooling fans cutting in and out and pulling the system voltage up and down. If the voltage compensation in the
ECU isn't set correctly this makes quite a difference to fuel delivery at idle when you have narrow injector pulse widths.
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robocog
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| posted on 19/5/10 at 08:53 PM |
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Heat soak on the air temp sender?
I guess easily monitored with a laptop and can of freeze spray at the ready
I know MS as std does overcompensate air temps and last REALLY hot day we had I was co-incidentally driving back from somehere and things got pretty
thin and weak and noticed a certain ammount of "surging" till speeds picked up and the temp sender saw some vaguely cooler moving air
Mounted sensor in a rubber tube to try and isolate it and keep it well away from the ally backplate and did get some exhaust wrap, but not fitted that
yet
I won't know if its helped untill we get another summer ;-)
Is your sensor into a chunk of ally that could be getting heat soaked?
I know you have ditched MS and gone over to the side with telephone support but still worth checking
Regards
Rob
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austin man
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| posted on 19/5/10 at 09:41 PM |
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do you have an air bleed into the inlet manifold ?
Just had to do this on the 2litre zetec turbo ticks over briliantly now. also had to fit one into a standard injected zetec
Life is like a bowl of fruit, funny how all the weird looking ones are left alone
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flak monkey
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| posted on 20/5/10 at 06:56 AM |
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Took the car for a run ths morning and its definately still playing up once its hot.
Very difficult to restart and keep running reading 18-20AFR on the dash at idle.
The air temp correction doesnt cut in until MAT of 60deg as it was causing other problems.
It could be something to do with the battery voltage compensation I guess. Once its properly hot the fan runs permanently (on at 88 and off at 82) so
it could be that.
Annoyingly I cannot find any battery voltage correction data for the Siemens Deka IV injectors I have fitted. 
Sera
http://www.motosera.com
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atspeed racing
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| posted on 20/5/10 at 07:24 AM |
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I think as we have both checked everything that could effect the mixture, perhaps you should have the induction system checked for leaks with an evac
smoke tester. This will find any leak in the induction system in minutes.
there must be a local garage somewhere near to you that would be able to do this, if you cant find anyone, drive down to us on Saturday and we will do
it for you straight away.
I dont think this is a software problem.
Alan
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NOTE:This user is registered as a LocostBuilders trader and may offer commercial services to other users
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flak monkey
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| posted on 20/5/10 at 07:32 AM |
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Thanks for that - I'll have a hunt around tonight and see if I can find any leaks anywhere.
Could it be the injector battery compensation?
The current values in the map are:
10v 119
11v 96
12v 78
13v 65
14v 54
15v 45
And from what i can find on the interweb the correct values for my siemens dekas are:
10v 92
11v 76
12v 64
13v 52
14v 41
15v 31
Which are considerably lower? I would have thought this would tend to make it rich though?
 
Deka spec sheet
[Edited on 20/5/10 by flak monkey]
Sera
http://www.motosera.com
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atspeed racing
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| posted on 20/5/10 at 08:22 AM |
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Dont get to complicated. Always start at the start!
We have never had this problem before and when you concider the amount of cars we do!
Get the induction system EVAC tested first as this will find any leak. You might be suprised just how many leaks you have.
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NOTE:This user is registered as a LocostBuilders trader and may offer commercial services to other users
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flak monkey
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| posted on 20/5/10 at 08:32 AM |
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Ok will do.
There is only 1 joint between the butterfly and the valve and thats where the throttle bodies meet the head. Will check everything is tight tonight
and go from there.
There's always one odd one - and its usually me!
Sera
http://www.motosera.com
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MikeRJ
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| posted on 20/5/10 at 08:54 AM |
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Are you running closed loop control?
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flak monkey
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| posted on 20/5/10 at 08:57 AM |
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No its all open loop now. No EGO correction at any point 
Sera
http://www.motosera.com
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graememk
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| posted on 20/5/10 at 11:09 AM |
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maybe this problem has always been there hence why the megasquirt wouldnt work....
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flak monkey
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| posted on 20/5/10 at 11:13 AM |
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Nah there is definately a problem with the old megasquirt. Phil at Extra EFi is testing it at the moment and I had a message last night saying that it
had just started playing up on the bench tester.
Oddly, I never had this problem with megasquirt, it always idled ok.... When I changed everything over I didnt disturb anything like the throttle
bodies/injectors etc.
Sera
http://www.motosera.com
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flak monkey
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| posted on 20/5/10 at 11:59 AM |
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Had a little more of a play over lunch time.
The problem doesnt start when the fan kicks in. Its maybe slightly worse, but only by around 0.3AFR.
I struggled to start it from 20deg but this is probably down to my cold start settings.
Once warm the AFR was around 12.5 when running well and 15 when running poorly. Again seems to switch between the 2 every few minutes.
Sera
http://www.motosera.com
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flak monkey
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| posted on 20/5/10 at 05:44 PM |
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Thats it, i am officially pi55ed off with this now.
No airleaks that I can find - like I say theres only one joint and thats got new gaskets fitted and the bolts are tight.
It always idled ok with the measquirt, no problems at all. Nothing mechanical has been disturbed. Now it wont idle properly or start when hot, or keep
running when hot when initially started for a few minutes.
There are no corrections affecting it in the ecu that I can see.
It goes from bein too lean to too rich every few minutes, never quickly.
None of the readings from the ECU are odd and none of them change when the problem starts. The speed drops and the ecu adds some ignition to try and
bring it back up.
I have increased the plug gap (stock is 1.6mm) and its not made any difference at all.
Oh and to top it all its due an MOT in a couple of weeks and it needs to idle properly by then!
Bloody thing.
Sera
http://www.motosera.com
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atspeed racing
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| posted on 20/5/10 at 06:39 PM |
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I know it isnt convenient to return back to us, but the offer is open for you to do so, no problem. We as a company pride ourselves on our work and
our reputation thrives on this.
You are more than welcome to visit us on Saturday morning and we can see what we can do for you.
Perhaps call us and confirm you are going to be here.
I have gone through the map and i cannot find any possible explanation within it to cause the strange problem you are experiencing.
- colin.
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NOTE:This user is registered as a LocostBuilders trader and may offer commercial services to other users
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40inches
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| posted on 20/5/10 at 07:05 PM |
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This may or may not sound stoopid, have you tried it without the bonnet on? If your setup is still as in your photo archive, with the filter behind
the manifold,and the tubing running under the manifold, may be heat soak? I had a similar problem on a tin top, the temp of the tubing was over 100c.
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flak monkey
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| posted on 20/5/10 at 07:30 PM |
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Happens with or without bonnet. Air temp constant at 55deg and coolant at 92 when ticking over for long periods. No changes when running well or
poorly. It happens at lower temps as well though. From coolant temps of 60deg upwards I would say.
I had it running for a few mins with it relatively stable, but seems just a fluke as without changing any settings its back to the variation.
OK a little more info...
The swing from lean to rich is consistently 65-70seconds
The swing from rich to lean is consistently 55-60seconds
This is without fail - times taken from timer on ECU.
I cant help but think its something electrical/ecu related as its so consistent in the swings and like i say the problem wasnt there with MS.
I also removed the dump valve and plugged vac line just to eliminate it - no difference.
Colin - getting down sat is not possible I am afraid, the 250mile round trip is a bit much. This isnt anything you have done, as you know it was doing
this before it came down to you. I was really hoping to be able to speak to Andy at Omex but he is away until monday.
[Edited on 20/5/10 by flak monkey]
Sera
http://www.motosera.com
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sebastiaan
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| posted on 21/5/10 at 07:30 PM |
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Hi David,
Why does the MAT correction only come in above 60 degC? The difference between 15 and 60 deg C is 15% in air mass! ((273+60)/(273+15)=1,15)
This means that, all else being equal, the AFR will also vary 15% without the MAT correction doing anything about it! This seems like a fairly sure
way to get possibly very damaging detonation. Depending on the control strategy employed, it could also have something to do with your idle problem.
Also, can you run the thing in closed-loop, and if so: why aren't you? The sensor isn't there for nothing....
Sebastiaan
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flak monkey
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| posted on 21/5/10 at 07:42 PM |
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It was over correcting and making it go lean at higher MAT like when sitting in traffic.
Under power the MAT is pretty stable at 25-35deg.
I know the theory says you need to remove quite a bit of fuel at higher temps but I always found MS took out too much fuel as well. So its safer to
run no MAT correction at higher temps as its less likely to randomly go lean...
Sera
http://www.motosera.com
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sebastiaan
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| posted on 21/5/10 at 08:25 PM |
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That just means you are not measuring the charge temperature correctly... OEM software often has a model that predicts the density of the trapped (in
the cylinder) charge, as that's also dependent on the temperature of the inlet system after the MAT sensor and a whole bunch of other
parameters.
If the theory doesn't correspond with practice, that does not mean the theory is flawed, just that you are not applying it correctly. 
Anyway, the above is all fairly arbitrary if it is possible to have the engine running in closed-loop. Is this possible?
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sebastiaan
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| posted on 21/5/10 at 08:27 PM |
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quote:
Originally posted by flak monkey
So its safer to run no MAT correction at higher temps as its less likely to randomly go lean...
I thought you said it only kicked in ABOVE 60 degC? I'm not trying to poke holes in your story, just trying to help solve the problem.
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