Cold start stalling

[scc.131.fe]

Mine did this for the first time today. Got half a tank of fuel in and haven't filled up since I last brimmed it a week ago.

Started perfectly on the second attempt. Interesting it also threw an error code and a check engine light. Plugged the code reader in, see attached.

Car had sat for a week since last start (not on charge and last use was a 55 mile drive) Cleared the codes and now all fine again.

Having built and mapped more than a few cars in my time the syptom seems to fall inline with the fuel pump not priming before start, and therefore not having fuel rail pressure to fire the initial injector priming pulse which is typically much longer than the pulse fired during running. You'd expect the pump to prime either when the drivers door is opened or closed (my old RS4, M140 and others have done this and you can hear it) or when the start button is pressed just before it cranks. This would also explain why it starts ok on the second button press as the fuel rails then have pressure and normally in a stall situation the pump would re-prime along with the priming pulse being delivered - and this kind of falls inline with the 'work around' where they are suggesting turn on the ignition and wait a few seconds before a second press to start.

Either way, if my thoughts are correct (which they may well not be as I don't know the exact set up in the Emira, yet) it would be software and not fuel related.

View attachment 51443

Good details! Anyone have a guess as to how rail pressure could be low on start without setting a P0087, P008A or similar code?

 

[Tobiasz17azs]

93 cold start , sometimes stall. 91 gas no problem .

 

[SSJAR]

I have had the cold start issue happen twice to me. The first time I have no idea what the conditions were and everything was fine after I turned the car off and then restarted. Yesterday, I jumped in the car, put the car into neutral (not using the clutch) placed my foot on the brake, and started the car. This was prior to the screens finishing their boot process. The car stuttered a bit and I immediately turned it off and it then restarted with no issue.

Also, I typically don't lock my doors, I say this because sometimes if they are locked and I unlock I can here some "things" going on in the car...

Based on some of the comments in this thread I got to thinking about the fuel pressure and I am by no means an expert so just trying a couple different options to determine what is happening. I use OBD Fusion to monitor the car when I drive. The fuel rail pressure at idle is about 50psi. On start up the readings go up to 90-100psi before coming right back down. Also, not sure how fast the bluetooth OBD reader is, so I could be missing some values as it is not updating quick enough.

The bluetooth adapter I use remains powered on constantly, I typically unplug it to not drain the battery, but I left it in to do some testing. This morning I went out and before opening the doors I connected my app to the OBD reader and the fuel rail pressure was at 32.6psi. I waited for the screens to start up and I did not see it jump up until I started the car and everything was normal. I shut the car off and even several hours later the fuel rail pressure was at 52.2psi.

I have attached some screenshots and I am going to keep testing different scenarios which might take a few days. What I am curious to see is if the car sits for a longer period of time, will that fuel rail pressure drop below 32.6 psi and if it does, when I get in the car does it jump up prior to hitting the start button on its own? For example, does pressing the clutch in or applying your foot on the brake send a signal to the fuel pump? Does waiting for the screens to fully boot give the fuel rail pressure time to rise? If I don't see any of those variables I will see if I can recreate a stuttering start and then look to see what the fuel rail pressure is.

Anyway, sorry for the long post and if you have any ideas or values you think might shed a light on this open to suggestions.

 

[NicolasB]

It's been probably over a year since I mentioned it is likely a low fuel pressure issue at startup. I had a car with this problem 25 years ago. Lotus had things pretty well dialed in with the Evora, then they went and tried to make it better and really failed.

 

[nimbus]

Whatever the underlying mechanical reason, it is definitely ECU related.

There was a group which purchased JUBU ECUs a while ago, and while that caused its own problems, one thing that stopped was stalling when cold.

It's probably related to some emissions tuning which aftermarket ECUs won't be obsessed with.

 

[EmiraHK]

Whatever the underlying mechanical reason, it is definitely ECU related.

There was a group which purchased JUBU ECUs a while ago, and while that caused its own problems, one thing that stopped was stalling when cold.

It's probably related to some emissions tuning which aftermarket ECUs won't be obsessed with.

While I agree that it is likely an ECU issue, more specifically an emissions tuning by Lotus resulting in different fuel tolerances, I think that many (including myself) have found changing the fuel used has helped in resolving the issue.

I have raised this issue to Lotus multiple times over the past year, but they have not once come back with a definitive answer, only to say "please update your software to the latest". Since I have not had the issues since switching fuels, I have not bothered to follow up since.