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Discussion Starter #1
So this morning as I started up my 05 Elise to go to work the engine stalled as I rolled down the driveway. This is very unusual. Then, as I steered the car to be parallel to the road, it stalled again. The CEL did not come on. It started up very easy after each stall. I noticed as I drove in to work that the few times I was stopped at a light, the idle is rougher than normal. The engine runs perfectly at speed, doing my 60 mile drive into work flawlessly.

A few months ago, the engine ran rough and the CEL went on. That problem turned out to be a faulty gas cap. I replaced it with a proper sized aftermarket cap and the CEL went off. Now the rough running has returned, but no CEL.

Might this be the same problem returning?

And is it common for an stall to occur with no CEL? Might that indicate a deeper problem?

Thank you.
 

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Hmmm, that's an interesting problem. Normally when a vehicle dies without a CEL the problem is something physical/mechanical (not a sensor or parts controlled by the ECU) that has failed, the first things I'd check are fuel delivery and spark.

Normally when a fuel pump goes bad they fail suddenly and completely; since the car runs better at speed I'd say the fuel pump is probably not the culprit. That still leaves other items in the fuel delivery system: filters, fuel pump relay (multi-function relay unit), immobilizer, inertia switch, fuses (R1, 20 amp; R2, 3 amp), and the wiring that connects them.

Ignition issues could cause the problems you describe, but the failure mode makes it a little less likely as weak or failed ignition coil (or wiring) could cause this and not trip a CEL.

Another area that can potentially be a cause would be the Idle Air Control (IAC) valve. If these get dirty they can become sticky and not move freely to where the ECU has directed, this can cause rough or unstable idle speeds. Many times a bit of carburetor cleaner can clean them up easily.

I'll attach a copy of the colorized wiring diagram I made for the 2005 Elise in case you need it for your troubleshooting. Good luck and let us know what you find.
 

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my car used to stall or get a really rough idle sometimes when coming to a stop. i don't recall if this was cold-start related. at those times, no CEL would accompany the misbehavior.

i do know that the car has a special fuel trim for idle conditions that is only adjusted under certain cases. maybe it's worthwhile to let the car idle for 15-20 minutes (after warmup) in order to let the trim adjust?

edit: also, i don't think this is indicative of a larger issue. i think this is just a normal behavior for a Lotus. it's endearing, right?
 

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2005 Elise LSS Saffron Yellow
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I'm old enough with enough high performance vehicle experience that the idea of complaining if it dies but restarts easily when cold is kind of amusing. You've obviously never dealt with something with a big cam and one carburetor barrel per cylinder.

That said, transient cold start conditions are the hardest to tune for. Everything (MAP, MAF, RPM, ECT) is changing at once, the conditions now probably aren't anything like they were the last time the car was running (Baro, IAT, ECT, EGO) so saved data are mostly useless, the ECU is managing a lot of interdependent variables simultaneously without much independent feedback, and it doesn't last very long before the operating regime changes (HEGO heats up quickly, which allows closed loop).

A lot of ECU code I've seen uses closed loop idle data to 'seed' the cold start open loop tables. If the base operating conditions have changed a lot since the last few cold starts, or the car didn't spend enough time at idle during warm up last time it might not have good data for the open loop tables to get refreshed, which is what Obeisance mentioned above.

Obeisance has been through the code pretty thoroughly, and it's definitely not as polished as any major auto manufacturers' strategies from 5-10 years before the 111R (Fed) came out. There's a lot of 'this worked last time' (when last time was a significantly different case) and 'let's put a bodge in here to keep this bad thing from happening' about the code. It's not surprising that it's a little kludgy and tends to spit and hiccup, especially given the big ports (low port velocity at idle) and cams (the low cam is still bigger than most anything available on a production car before VVT appeared) these engines have. As Obeisance said, it's part of the sports car charm.
 

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Discussion Starter #5
i do know that the car has a special fuel trim for idle conditions that is only adjusted under certain cases. maybe it's worthwhile to let the car idle for 15-20 minutes (after warmup) in order to let the trim adjust?
^^^Thanks for the idea. I'll give that a try.
 

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Discussion Starter #6
Hmmm, that's an interesting problem. Normally when a vehicle dies without a CEL the problem is something physical/mechanical (not a sensor or parts controlled by the ECU) that has failed, the first things I'd check are fuel delivery and spark.

Normally when a fuel pump goes bad they fail suddenly and completely; since the car runs better at speed I'd say the fuel pump is probably not the culprit. That still leaves other items in the fuel delivery system: filters, fuel pump relay (multi-function relay unit), immobilizer, inertia switch, fuses (R1, 20 amp; R2, 3 amp), and the wiring that connects them.

Ignition issues could cause the problems you describe, but the failure mode makes it a little less likely as weak or failed ignition coil (or wiring) could cause this and not trip a CEL.

Another area that can potentially be a cause would be the Idle Air Control (IAC) valve. If these get dirty they can become sticky and not move freely to where the ECU has directed, this can cause rough or unstable idle speeds. Many times a bit of carburetor cleaner can clean them up easily.

I'll attach a copy of the colorized wiring diagram I made for the 2005 Elise in case you need it for your troubleshooting. Good luck and let us know what you find.
Thank you for the attachment, but that's way beyond my pay grade. I'm not able to work on this (or any) car. Maybe in the next life.

I'm hoping that a CEL goes on so that I can take it to the shop for a repair. I would hate to do so without the CEL because odds are nothing can be found.

We'll see how it goes.
 

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Have you ensured that the gas cap is correctly installed and tight?
 

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Are you sure there's gas in the tank? A hill will move fuel from the pickup. Happens... don't ask how I know.
.
 

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Engine Stalling

Hi, my 2012 Elise S used to stall intermittently. Most of the time of the stalls, there were no check engine light either. Most of the stalling would be in low speed situations ie carparks and coming to a stop sign.

After months of on and off and replacement of parts such as O2 sensor, fuel injectors, maf, etc which only helped for a few weeks and then stalling would start again!

It finally decided to stall one day so significantly ie at every stop light! and then threw up a CEL which was related to the maf sensor. As the Lotus mechanics had already changed the maf sensor, it was diagnosed as engine wiring harness being faulty. This was replaced and there has been no issues of stalling since. This is now at least 3 months of daily driving.

Can I suggest to pull out the connectors and use contact enhancers to see if it could be related to bad/old connectors? Hope my experience helps.
 

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Discussion Starter #13
Hi, my 2012 Elise S used to stall intermittently. Most of the time of the stalls, there were no check engine light either. Most of the stalling would be in low speed situations ie carparks and coming to a stop sign.

After months of on and off and replacement of parts such as O2 sensor, fuel injectors, maf, etc which only helped for a few weeks and then stalling would start again!

It finally decided to stall one day so significantly ie at every stop light! and then threw up a CEL which was related to the maf sensor. As the Lotus mechanics had already changed the maf sensor, it was diagnosed as engine wiring harness being faulty. This was replaced and there has been no issues of stalling since. This is now at least 3 months of daily driving.

Can I suggest to pull out the connectors and use contact enhancers to see if it could be related to bad/old connectors? Hope my experience helps.
Thank you very much for sharing this. I will use this information should I bring the car in for work on this issue. Again, many thanks.
 

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My first instinct is a small vacuum leak.

Assuming the behavior repeats.

I've had my car not want to start or stall, but not on a regular basis

If it continues I wold be more suspicious of an actual issue than an ECU glitch.
 

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To pinpoint vacuum leaks, attach a thin(ash) hose to gas/butane cartridge and move the tip around slowly.

To discern general area, ppl spray carb cleaner or other flammable stuff.
 
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