Request for advice, car won't idle

[John Vine]

#100:  Thinking more about this...

On an RB-equipped car (such as mine),

Throttle Angle Increasing voltage = 5.0v - Throttle Angle voltage:

Green trace = Throttle Angle
Blue trace = Throttle Angle Increasing

The values under the vertical pecked line are 3.23v and 1.77v respectively.

On a plenum-equipped car (that is, with anticlockwise TPS rotation), does the Throttle Angle Increasing panel show the same actual TPS voltage as the Throttle Angle panel?  And if so, do the voltages increase in tandem?

Could someone with such a car (James/aerobod perhaps?) possibly check this?

JV 

[aerobod - near CYYC]

Hi John, you are correct, the Throttle Voltage and Throttle Voltage Increasing are the same for the plenum system, cursor is shown at 3.74V for both:

[John Vine]

Thanks, James.  You're a star.

JV

[StevehS3]

Just reading up on this topic and I wondered if the first step in setting the idle should be ensuring the throttle stop is correctly set ie the opening at idle is correct before adjusting the tps to suit. I am referring to the standard single butterfly throttle with plenum. If the opening is isn't correct would the ECU be desperately trying to correct the idle with ignition advance (when the problem is too much/little airflow) and the mapping would be slightly out too as the throttle opening would be slightly different/incorrect. 

[aerobod - near CYYC]

Without remapping the engine, there isn't much leeway in setting the idle stop, Steve. It is an iterative process to check that the idle fuel trim is minimal (i.e. actual Lambda when warmed up in closed loop is as close to target Lambda as possible), idle speed is stable at target idle speed and Throttle Site is in the range of 0.0 to 0.4 (otherwise the ECU will not detect the engine being at idle). Throttle Site should also not be trying to dip below 0.0 voltage (indicated by the panel turning red and as such going into TPS failure mode).

The TPS has very slight adjustment in the slack of the holes to the tune of about 0.02V, so mechanically there is little leeway in the position the stop can be adjusted to that will meet the above criteria. Beyond that adjustment will require ECU remapping.

[StevehS3]

Thanks James. That all makes sense but it does seem a bit marginal and sensitive. I suppose that's because it doesn't have the standard Ford throttle, ECU and idle air control. Fortunately on my 310R it all seems ok so best not to tinker! 

[John Vine]

#105  Throttle Site should also not be trying to dip below 0.0 voltage (indicated by the panel turning red and as such going into TPS failure mode).

I didn't realise that was possible.  But another advantage of RBs perhaps, where the voltage decreases from idle.

JV

[AlastairA]

Thanks all - my car is being collected for PBC today and I have informed Caterham of the issue. They have said they will investigate and let me know the outcome - I'll report back here what they say and also see if I can glean some information about how they make initial adjustments of the TPS.

Best, Alastair

 

[Rich Goddard]

#108 Alastair, I'm very interested to hear what info you manage to get out of CC. 
 

Does anyone else with a Duratec (plastic plenum, standard locked ECU) find it impossible to permanently set their TPS/idle position to anything less than Site 1.0? By slightly slotting the fixing holes on my TPS, I can rotate it a small amount and get Easimap to temporarily show Site 0.0, but then every time I use the battery master switch to power-down and power-up it seems to reset and defaults back to Site 1.0.

Interested to know whether others with similar set-up have the same issue, or whether I’ve got a hardware or software problem.  Is it a standard default reset setting by CC?

After a LOT of trial & error, rude words and steep learning curve (thanks to threads like this) I've managed to get my car to start and idle from cold, but it's pretty lumpy.

[John Vine]

#109:  Did you manage to resolve the sticky butterfly problem you reported in #92? 

JV

[Rich Goddard]

#110:  Yes I did, thanks John.   I gave it a thorough flush-through twice, getting rid of an accumulation of dirty oily gunk.  And as a result I've since installed the oil breather re-route (thanks to your other thread/parts-list on this) to the catch tank to hopefully avoid future oil deposition in the plenum.   While doing that I realised that the throttle blade only sticks when the blade is fully closed and comes into (light) contact with the housing....and I determined that with the idle stop screw set to a position which allows enough air flow for my car to idle (albeit in a lumpy way) it never fully closes and so doesn't make enough contact to stick....which I suppose is obvious really. 

[John Vine]

#111:  IMO, the blade should always return freely to rest firmly on the stop, and never stick at any point.  Could your throttle body be slightly distorted? 

Would swapping out the plenum/throttle body with a known good one help diagnosis?  I guess there are a few second-hand ones around following RB upgrades.  Maybe someone would be prepared to lend you one just for testing?

PS:  Glad the breather thread was a help. That little mod was getting on for 15 years ago, I guess.

JV

[AlastairA]

#109: Rich I will indeed report back what CC say about my car and whether they manage to make any improvement over and above my uninformed and amateur efforts.

One thing that struck me when I read your note was something that was reported by John Martin (aka purplemeanie) on his website - he went to a professional who (if I remember correctly) stated that sometimes the issue is caused by the ECU not be programmed with the correct Throttle Site 0 position. This was remedied by inserting the ignition key and turning ten times over from ignition positon 1 to 2 and back again. Apparently this causes the ECU to reset the throttle site position. I tried this on my car and it made no difference but I think my issue is more related to the throttle body being completely closed. However, I wonder whether this might be relevant to you? I can try to find John's blog page if that is of interest.

[aerobod - near CYYC]

There is no function in the MBE ECU that I can see that will do a throttle reset, Alistair. I think John's reset procedure is for a different ECU.

Looking at my unlocked MBE 9A4 ECU and trying to explain Rich's low TPS voltage at idle and Throttle Site initialising to 1.0, I think I may have found out why. As the car went through an upgrade, I think it has had a remap using features that Caterham don't seem to use in the standard map. I think it has been configured to use TPS % to resolve Throttle Site, with a lower than usual voltage (compared to the norm for Caterham) for the idle setting. These are the configs with the throttle Site set by TPS % that I have in my unlocked ECU with the feature disabled, notice the 0.28V default lower voltage for Throttle Site 0.0.

There is always the possibility that Caterham did a completely different map on some cars with the MBE ECU, but I think it is more likely that a custom map with custom features was used on Rich's car.

 

[AlastairA]

Thanks James - I am on a very steep learning curve here!! I re-read John's blog just to see if he references the ECU model, but I didn't see it any where. It is a 2019 420R kit though and for anyone who is interested, here is the relevant page (scroll down past the flat-flooring description) : Link

Cheers,

Alastair

[aerobod - near CYYC]

Hi Alistair,

It looks as though John's car would have an MBE 9A4 ECU. Unless Caterham has some specific features added, the latest Easimap software has no means of dynamically setting the TPS range when looking at the config for my 9A4 ECU. This could be verified on a locked ECU by comparing the TPS raw voltage with the throttle site at idle and full throttle with the engine switched off. If before a "reset procedure" and after it is completed a comparison is done, then the throttle site should change relative to the voltage. What the reset procedure may be doing though is clearing adapted fueling for closed-loop Lambda operation, which is nothing to do with the TPS alignment, but will have an effect on the engine idling when warmed up.

Overall the TPS voltage itself doesn't matter from a fuel map perspective, it is the throttle site that the voltage is mapped to that determines the engine fueling, so any mechanical adjustment (i.e. throttle stop or TPS rotation) should be made to get the throttle site to the correct value, as opposed to the voltage to a specific value.

[aerobod - near CYYC]

One thing that has always been a best practice is to set Throttle Site for idle to be between 0.0 and 0.4, but just looking through the configuration options, the Throttle Site below which idle is deemed to be occurring is actually configurable. I think the way to determine what Throttle Site Caterham has set to determine whether it should apply idle conditions can be probed by showing the "Idle Speed Status" Panel, then increasing the throttle position until the status changes to showing the engine to not be in an idle state. This is the info it states about the Idle Speed Status Panel:

'This is a bit field which reports if idle speed control is happening and if not why not. Only if all bits are zero will idle speed take place. The eight bits are defined as follows from left to right: Not Used; Not Used; Not Used; Delay After Start; Road Speed Too High; Engine Speed Too High; Pedal Position too High; User Disable'

Any mechanical idle adjustment should also be done with the "Target Idle Speed" panel showing to ensure the correct value is attained and the actual engine speed is within a few RPM of that value, otherwise the idle can hunt around the target value.

If the Throttle Site can be increased to a higher value than 0.4 and the ECU still shows an idle state, then there is more flexibility to change the throttle stop or TPS position.

[StevehS3]

James, assuming the idle control is achieved by the ECU adjusting the ignition timing to maintain the target RPM, I have been wondering whether setting the throttle stop should be done with an eye on the ignition advance (so that the ECU has a good working range of ignition timing adjustment to achieve the target RPM and with a reasonable amount of airflow). Although, I note what you said earlier about there being little leeway with the throttle stop position in any case.

[AlastairA]

Thanks James - so helpful.

John has kindly agreed to lend me his MBE cable should CC not diagnose or fix the issue - in which case I'll follow your instructions and recommendations. It'll be a few weeks until I see my car again though (PBC, IVA, Registration etc etc)!

[Rich Goddard]

Interesting new information James. (Well, new to me anyway)

However, I've just plugged my ECU in and been into Easimap 6 and I can't find the "idle speed status" or "target idle speed" panels so I think that may be because my ECU is a locked 992 unit. 

[aerobod - near CYYC]

Re #120, Hi Rich, have you set the mode to "Advanced" as opposed to "Basic"? Click on the Profile at the bottom right, then select Advanced Mode. Here are the SBD instructions, if my instructions are a bit confusing: https://www.sbdmotorsport.co.uk/app/uploads/2021/06/Easimap_6_Basic_to_Advanced_User_Instructions.pdf

That being said, I looked at the most recent 992 ECU files I have in my Easimap install (992ac80b.ec2 from Dec 2009) and it didn't have the Idle Speed Status Panel available when I loaded the file to Easimap on my PC, I'm not sure if there are any more recent files available or if they will have the function, either, as SBD doesn't seem to have archived EC2 files for the 992 for download.

[aerobod - near CYYC]

Re #118, Hi Steve, there are ignition advance defaults for idle speed setting in the 9A4 ECU, my unlocked ECU has the minimum ignition idle advance set to -15 degrees (ignore the -40 degrees target advance, it is only used if there is an Air Control Valve) and an ignition-only idle control strategy:

My idle is generally stable at 1,000RPM +/-10RPM, with not a lot of variation in the ignition advance, -8.5 +/-2 degrees is the typical variability:

[John Vine]

#121:  I've just looked at my version of Easimap (R76) and the latest 992ac80b.ec2 file (with Advanced Level 1 profile), and there's no Idle Speed Status panel that I can see.

JV

[aerobod - near CYYC]

Re #123, Hi John, I just looked back through old ECU files, it looks like the feature was added to the 9A4 ECU in version 9A4ad19b on 20 Jul 2009.

Although the latest file date I have for 992ac80b is 11 Dec 2009, the actual last feature update time in the file is 7 Nov 2008 (Observed in Windows Explorer in the 'Description' Field). I don't think the 992 ECU had any later version than 992ac80b, as far as I can see, so this very useful feature is not available on the 992 unfortunately. The interesting thing is that my 2012 car had a 992 ECU loaded with 992ab94k, which has a date stamp of 24 Oct 2006 in it.

[AlastairA]

Just had feedback from my PBC at Caterham Gatwick. The engineer confirmed that a small tweek was required to the TPS to prevent the engine from hunting in a cold start. He also let me know that Easimap was used and that the base map always needs tweeking a bit.

Hopefully this just confirms all the excellent knowledge and advice provided on this thread - thanks all.