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Request for advice, car won't idle


CtrMint

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Guys,

Last night I went out for a run, ended up coming over the mountain road pretty quick.  Then pulling away at a set of lights in Onchan I stalled and struggled to start the car, I could only get it to run with plenty of throttle reving.

I've tried to start the car this evening and just won't idle after the initial fire.   It sounded to me like it wasn't attempting to idle at the normal 1k to 900 rpm.  I've readjusted the adjuster on the throttle cable, and its brought idle back up and the car now starts and runs as normal, a lumpy idle until warm.

Is this likely to be a simple case of the throttle cable adjuster winding itself out from the vibration of the engine at high load,  which was as a result of a quick drive?  I noticed the rubber sleeve was forward of the threaded section?  Does that help prevent this?

Common issue?

Or should I look for something else, like I say I think it is fixed, just want to be safe than sorry.

Sorry if its obvious.

Just add to this if you let the car drop before 1k, it stall pretty quickly, something its not done previously.  I've taken the battery off now, as I've seen previous comments about the ECU/throttle stop and map, not that I've altered that.

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That could explain the problem, but it is more likely that the throttle stop locking nut came loose (may have also dropped off) and the screw backed out, best to put a bit of blue locktite on it. By adjusting the cable you got the throttle back to the right position, but it really needs that bit of slack that you had in it to ensure the throttle stop defines the idle position.

 

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The throttle stop nut is there and is certainly finger tight, I'm very cautious about messing with it so didn't touch it.

You are correct, the throttle position is now sat above the stop, at idle which is ~1k.  Sounds like I need to raise it a bit and then reconnect the battery.

 

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Yeah, will order tomorrow.  I guess the Easymap will show me any other sensor values out of range or bad etc.

This situation is a bit weird, it's not the first time I've driven the car quick.  When it stalled last night it refused to start initially, not sure if I flooded or something trying to get it going we traffic behind. 

The engine does sound normal, once running, so I'm not too concerned, also oil pressure is great too.

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Yes, lots of good info with Easimap. You can also do logging of all the available sensor and ECU parameters, take the car on a run with a laptop in the passenger footwell or on the seat held in place by the seatbelt, recording the data. With my unlocked ECU (I replaced the standard Caterham one to get easy tunability), I've even done some ECU re-mapping on the road from the passenger seat while my son drove the car to my orders. Your OBD/CAN port should be under a large rubber grommet in the angled panel below the dash. On my left-hand drive car it is on the drivers side, not sure if this switches side for RHD cars.

I'm running Easimap on Windows 10 on my cheap garage laptop at the moment, but the software will run on a Windows virtual machine too - most data analysis I do is on the more powerful Linux workstation I have with Easimap on Window 10 on VirtualBox on Fedora 30.

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I'm going to install Windows 10 on tin using a Macbook Air, I've currently got it running under Virtualbox but its a little slow and for a 20 quid license I may as well go native, rendering the performance of the Air.

My personal preference is Ubuntu with KDE Plasma 5, so much so I've replaced my MacOS on a 27" iMac.  I'm my professional world Debian is always the preferred OS, and Ubuntu is just that little bit easier on the user.

I've been looking into building my own shift light system and data logger.  I'm not a fan of the shift lights sold by CC, it seems large and a bit 1980s looking.  My aim is to use a Raspberry Pi as a SoC, then use a GPS hat, OBDII usb reader,  displaying data on a small OLED screen.  I also wanted to pick up the RPM feed, though I'm, shall we say trying to get the courage to interfere with RPM tacho feed.  I've also lost a little interest due to the apparent non-standard nature of the ECU, so we're told.

That's all a bit of an aside from the original post.

I've just been back out to the garage, having let the car cool completely.  

I reconnected the battery, tried starting it again, and it's back to being reluctant, just won't idle  Sounds temperature related.  

 

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  • 4 weeks later...

Having sorted the leaky radiator through replacement I managed to get out in the car this evening and found it again wanted to stall.  It's still idling poorly and as a habit of stalling when pulling up to a stop.  I thought I'd solved this.

I've not managed to source the MBE cable yet, at 140GBP it's pretty expensive.  

I already have what  I believe is a CAN Bus to USB cable in the form of one of these;
https://www.evoscan.com/evoscan-gps-obdii-cables/details/13/1/performance-vehicle-pc-diagnostic-interfaces/openport-13d-usb-obdii/mutiii/ssmii-datalogging-cable

I can't find anything specific on the SBD MBE cable, but I'm assuming its a similar CAN bus style cable, although there is a box of tricks.  

Does anyone know a little more about the MBE cable?

Thanks

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Physically the MBE cable with CAN to USB converter is the same as used in OBD II implementations, as is the connector. The problem is that it doesn't use the OBD II protocol that would be expected by most automotive aftermarket software and conversely the aftermarket OBD II to USB cables will be outputting OBD II packets that the Easimap software is not expecting.

You could probably write your own device drivers to use an aftermarket cable to output the proprietary packet payload in the CANbus messages that Easimap and the MBE ECU are using, but MBE haven't published any documentation on their packet protocol, as far as I know.

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Ctr, once again, I don’t think you’re finding anything unusual. My R400 was like yours sounds when I built it in 2016 and I’ve heard of many the same. 

In the end mine was set to idle at 1200 and it used to hunt around at that, and still wouldn’t idle until it had run for a minute or so. 

The solution for me was to fit RBTBs and have it set up properly; I’m not suggesting you do that (though I found it well worth while!) but I’m sure you can find a way to have it sorted better than it is now. 

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Minty, I too have the same "problem" if you can call it that. New 420r last year, factory built. It's never idled from new so on start up I just throttle it a for a minute or two and all is fine. 

Funnily enough, I have experienced it wanting to stall after high revving then coming to a halt. I mentioned it to Oakmere when in for a service but it's still the same...

I've learned to live with it. No big deal.

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Limitless, yes mine has started that too, it wants to stall after moderate to hard running and not for long either.  It never did this before.  Up to 2500 miles the engine ran faultlessly, yes I had problems with the rad fan and other challenges.  But the engine always ran fine, now the sudden change is a bit weird.

The TPS seems secure and so I can't see how that has moved. I'm wondering if its the 02 sensor, with the amount of brutal overrun bangs that come through the exhaust, might that have killed the 02 quickly?  Googling some of the symptoms for a dead 02 sensor certainly sound similar.

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When the lambda failed on my K it wanted to stall at junctions when the revs drop and it struggled to pass the MOT. I plugged a ODB reader in and it told me the heater had failed in the lambda. Swapped it out and it ran perfectly as before.

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I'm no expert, so please take my response with caution, and I'm currently googling etc.

But as I understand it, disconnecting the lambda should force the car into its closed loop state.  If so, and if the lambda is at fault then the car should improve its idle etc.  If it doesn't then it might point to an issue elsewhere such as the TPS etc, suggesting the lambda is fine.

The other option is to buy the MBE cable and watch the value in Easymap which I believe should oscillate between two values, sorry can't remember what.  From my research I believe the ECU has to keep changing the mixture slightly to permit the O2 to determine the difference between ambient and that in the exhaust.  Well that's my understanding.  If the value is static or way out then it would indicate the O2 at fault.

May be someone with more knowledge can add some more here?

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