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Discussion Starter #1
I had a search on the topic and didnt come up with much at all.

I have a 06 exige with '10 sc kit inc ecu etc

all has been running well for 15k, just seems to be getting worse now.

If I start the car in the am it will catch fine but the idle is too low for 10 seconds or so and then seems fine, warm or hot start its normal. Once it did stall but started first next attempt.

Id say the idle is around 700rpm at cold, maybe 650...

Any thoughts, cheers.

Ian
 

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Mine is doing pretty much the same since last summer.

I think it is related to the fuel pump not priming fuel correctly before cranking the engine on a cold start.

There is a sequence with the keyfob for the alarm system and I think this is causing the problem.

Make sure you can hear the fuel pump well pumping before starting the cold engine.

You can do the procedure twice to make sure the fuel pump worked 2 times and then start your engine and see if the first 10 seconds is idling better.

Mine seem better when doing this.

Otherwise it look like my engine was running on 2 cylinders for the first 5-10 seconds and very low RPM then going back to normal after.
 

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Discussion Starter #3
Mine is doing pretty much the same since last summer.

I think it is related to the fuel pump not priming fuel correctly before cranking the engine on a cold start.

Make sure you can hear the fuel pump well pumping before starting the cold engine./QUOTE]

Thanks, that could be it, i'll try letting it prime twice. cheers
 

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Discussion Starter #4
It doesnt seem related to the fuel pump as I can hear it prime and I wait, then hit the start button. Still sounds like it runs on 2 cylinders for several seconds then settles... If I immediately turn off and start again it starts fine and healthy.
 

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It is not related to the sparks plugs also.

I did change mine for those iridium NGK recommended by BOE and nothing changed .

When I do make sure my fuel pump do his cycle before a cold start, my engine is not idling on 2 cylinders anymore.

But it is idling low at 1000 rpm like if the engine was already hot.

It look like if the ECU had lost his choke function memory for cold start. :scratchhead:

I'm on my way to get a torque300 tune next month so I'll see if it will correct the situation.

Before my car had a higher idle speed when cold ; I'm pretty sure your car have lost this function too.
 

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Discussion Starter #6
Yes its like it has lost the choke, but its 25deg celcius here in the am and it always clears after 5-10 seconds so its not the temperature i dont think. I am taking it in for a service soon as its due for more than just oil/filter changes, Ill let them sort it out. cheers
 

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Let me know if you're dealer put the finger onto the problem.
 

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My Elise did this from the time I got it. It did it on the Stock tune, the BOE NA TorqueTune, and on the Sector111 Katana2 tune. I installed a fuel surge tank/pump and the problem went away so I think there might be something to the fuel priming issue noted above. I am now running the BOE Torque250 Katana tune, but that went in after the surge tank fixed the problem.
 

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Discussion Starter #9
Will do NoFear99, Thanks Nickshu, is does seem to be a priming type issue or at least it could be. If I tap the starter button once to turn over the motor but not enough for it to catch and then hold it to start it starts crisper and idles normally it seems... goes in next thursday, I will post up what they found.
 

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Will do NoFear99, Thanks Nickshu, is does seem to be a priming type issue or at least it could be. If I tap the starter button once to turn over the motor but not enough for it to catch and then hold it to start it starts crisper and idles normally it seems... goes in next thursday, I will post up what they found.
Have you been to the garage today ?
 

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Discussion Starter #12
Well the garage didn't find anything unusual and wanted the car overnight which I couldnt do this time. Currently I am using a start procedure which is simply to tap the start button twice then press and hold, starts normally then. Thoughts>?
 

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Mine has been doing the same thing. 05 with BWR supercharger. Only on cold start I have to hold slight throttle for 10 seconds then it starts to purr with no problems. If I go to the store come back out fires right back up no issues.

I replaced spark plugs
Cleaned MAF censor
Checked battery connections
Listened and confirmed priming is happening (even tried doing the cycle multiple times before pressing start button)

Any success or ideas?
 

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I've had this issue for a while now as well and a Fuel Surge Tank didn't solve the problem. However we believe we've tracked it down to a bad check valve in the fuel pump as fuel pressure drops slowly from the fuel rail when the car is turned off. Apparently the check valve prevents the fuel from draining back into tank and maintains fuel pressure. We are going to try and put an inline check valve close to the pump to see if it solves the problem. Will report back once I get one installed.

Cheers,
Zoomby_U
 

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I purchased a '07 Exige with 5700 miles and it has always had the 'stumble' problem for 7 to 10 secs.
I'm convinced it is as zoomby_u suggests. The fuel is draining out of the fuel rail over time and needs to be replenished on cold start. The reason I believe this is once I pulled the car out of the garage to wash and experienced the 'stumble'. I moved it 10 feet, washed and pulled it back in the garage 30 mins later. Started without stumble.
I'm not sure what to do about it as I don't know replacing same fuel pump will solve the problem long term. I'm anxious to hear back from zoomby on inserting a check valve.

For now, it's annoying, but doesn't prevent me from enjoying the car.

Larry
 

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Whenever I have stored mine for awhile, I just turn the key and wait till after I have heard the fuel pump cycle, then I turn the key off again,then back on, and then once the fuel pump has cycled, I start, never a stumble, regardless of how long I have stored it.

Actually, before I even do that, if it has been months since I have taken it out, I take the fuel pump fuse out and turn the vehicle over a few times to try to sling a little oil about, then the above "procedure" heh
 

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My car just started to develop this symptom. 2005 VF1 s/c 28K miles. It all started when number 1 coil went bad. After 5 seconds of blahp blahp blahp the idle surges then returns to normal. Again after running only a minute and restart, it is fine. I will try the double click start to see if it makes a difference. Fuel pressure is stable and short and long term fuel trims are good and no lean codes even after sustained high speed pulls on back straight. Check valve could be a possibility but would need to locate that. Thanks Tommy
 

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I called my local Lotus dealer (Denver) and asked about the stumble problem. The service manager said, "Oh yeah, they all do it. By the time you get your set belt in place it'll be ready to go" Argh.......not the right answer.

I asked if there were any tech bulletins from the factory and he said no. Dealer isn't interested in digging any deeper into this problem. Disappointing.

I called BOE and the guy I talked to hadn't heard about the problem.Surprised. I think they might have a business opportunity, if they could put some engineering minds behind it.

Appears most think it's an annoyance but not worth spending any serious time on.

I also joined the "ToyotaNation" forum and put the question to the 2zz-ge guys. Several responses, but didn't seem to know of the problem with their motors. All they could offer was Lotus uses their own ECU programs.

Larry
 

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Larry, it all may be just TADTS. As I have an aftermarket setup and tune this my be a result of a cold start initiation sequence. If it does not hinder performance I can live with it. Hell its Halloween maybe its just a LOTUS curse. Hahaha Yes I know it is frustrating but you do not want bigger issues. Tommy
 

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This thread started more than a year ago, but for many, the problem persists. In my experience, this nuisance condition has two typical causes.

Many fuel injection systems have a check valve somewhere (or sometimes more than one) to keep the system near operating pressure when it is shut off. The check valve may be a stand-alone item, built into a fuel pump, or it may be built into a pressure accumulator (as in some Bosch systems). If this check valve leaks, fuel typically returns to the fuel tank. I’ve had fuel pumps with integral check valves fail where the pump still pumps but the check valve won’t hold pressure.

A second cause is leaking injectors. Pressure on the fuel rail is held in check by a closed injector, but the injector can slowly leak down into the intake manifold. Not only does this result in loss of fuel pressure, it also creates an over-rich condition on startup that will cause rough running until the excess fuel is burned or exhausted. I have replaced “perfectly good” fuel injectors several times and eliminated this problem, only to have it return 6 - 12 months later if the vehicle sits for two or three days. I’ve given up on fixing otherwise serviceable slowly leaking injectors . . . the cost isn’t worth it to me.

Glen
 
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