Engine idling too fast, running rich, no fault code!

[garymb]

The engine warning light is on and the engine is idling at high revs. When driven the exhaust is popping and banging much more that usual and my sense is that it is running very rich.

However when trying the paper clip trick with the ALDL there is no fault code. Even more surprising though, I don't even get the 1,2 code to indicate it has entered diagnostic mode. The warning light just stays solid amber. This is worrying as I'm guessing this might mean the ECM might be screwed. The car has the stock ECM, and no mods.

This problem has happened intermittently a few times recently, seeming to clear itself after 10 minutes of running-- but now seems permanent. The car will go reasonably well, though not as fast (no misfires) but a bit sluggish which I put down to the rich mixture.

I could buy a new ECM from SJ but if damage to the ECM it has been caused by some other problem presumably the new ECM might be also be affected. And of course I'm reluctant to replace it until I'm sure that is where the problem lies...

Do the ECMs have a finite life? Is there an possibility of moisture causing a problem (recently drove in a deluge)?

Any thoughts?

[ailwyn]

Change/check your Coolant Temp Sensor (CTS).

--Edit, just re-read your post... does sound like a duff ecu

Is there anyone close to you that can swap ECUs to check that it's at fault?

[garymb]

Change/check your Coolant Temp Sensor (CTS).

--Edit, just re-read your post... does sound like a duff ecu

Is there anyone close to you that can swap ECUs to check that it's at fault?

That would be good. Has anyone else had the ECM just fail.?

Mines a 1990 model so it would be about 18 yrs old.

[Dave Eds]

Gary - get in touch with DaveT as he is near you and may have spares from CJD or you could try the ECU from his current car

[garymb]

Hi

Thanks for your advice and help.

I've decided that I'm pretty certain it's the ECM, and if not I'm going to need one soon anyway or at least a spare.

Managed to source one from South West Lotus Centre for £150 + VAT. They say that they are getting increasing numbers of Elan and Esprit owners asking for these after about the 15 yrs period, so they obviously begin to degrade eventually.

They have over 40 in stock (non-cat turbo) if you need one.

Anyone have any hints or tips for fitting?

[Enright]

It's recommended to disconnect the battery while doing the job.

You might find it worth doing that anyway, just in case it resets it.

It's very odd that your car is still able to run and yet won't produce any fault codes - I wouldn't have thought that a partial failure of the ECU was possible.

[garymb]

it does seem odd that it should be able to run (albeit not that well).

Just started it again this morning and there was no warning light. Switched off and re-started and there was the warning light, it was idling too fast but I still couldn't get an error code afterwards. I did try disconnecting the battery yesterday for a few minutes to see if I could get it to re-set. I'll try again but for longer and let you know, but I'm guessing a minute or so should be enough...

[Enright]

Just an obvious one - do you wait for a few seconds between turning the ignition from the "dash lights on" position to cranking the engine?
You need to hear the fuel pump finish priming or it does tend to p!$$ it off a bit!

[GeoffSmith]

Certainly sounds like the ECU - have you checked all the connections to make sure they are all good?

BTW, I wouldn't mind an ECU to play with so please don't throw it out - I may even be able to repair it.

Presumably the SW Lotus ECU comes with a memcal as it states non-cat turbo. I've recently been talking with Dermot on LEF about memcals as the limphome hybrid is Lotus specific, so it doesn't bear thinking about if these start failing.

[garymb]

Just an obvious one - do you wait for a few seconds between turning the ignition from the "dash lights on" position to cranking the engine?
You need to hear the fuel pump finish priming or it does tend to p!$$ it off a bit!

Yes, I usually wait for the fuel pump to finish whirring before cranking the engine

[garymb]

Certainly sounds like the ECU - have you checked all the connections to make sure they are all good?

BTW, I wouldn't mind an ECU to play with so please don't throw it out - I may even be able to repair it.

Presumably the SW Lotus ECU comes with a memcal as it states non-cat turbo. I've recently been talking with Dermot on LEF about memcals as the limphome hybrid is Lotus specific, so it doesn't bear thinking about if these start failing.

Yes, I assume this comes with a memcal (I assume it all comes in the steel box) I did stress to SWL that this is a non-cat turbo although I'm not sure I entirely follow you Geoff-- is the memcal where the limphome data is stored (pardon my ignorance)? Definitely wont throw the old one out and provided that it definitely proves to be duff I'd be happy to let you play with it Geoff-- especially in the light of the fact you've helped me out many times

[Rambo]

£150 + VAT.

Pity you weren't at Donny this year - SWL were flogging them for £125 cash and no Vat. From memory they were only £100 the year before because Dico was thinking of getting one

[RayD]

Is it worth trying the engine in service mode ( put the clip in while the engine is running) I wonder? Just to see how smoothly it runs, or not, and what revs it's doing.

Ray

[Monty]

£150 + VAT.

Pity you weren't at Donny this year - SWL were flogging them for £125 cash and no Vat. From memory they were only £100 the year before because Dico was thinking of getting one

I got Dico one last year at stoneleigh for £100 no vat

[GeoffSmith]

Yes Gary, the limphome is plugged into the memcal which is plugged into the ECU which is then fitted with seals. The ECU is identical but the memcal determines which engine/setup it controls.

[garymb]

Is it worth trying the engine in service mode ( put the clip in while the engine is running) I wonder? Just to see how smoothly it runs, or not, and what revs it's doing.

Ray

Yup, I tried that-- it made no difference. The odd thing is that although it's idling very fast both (with the clip in and out) it's runny pretty smoothly-- no misfires, but very rich I think. The exhaust pops and bangs like mad if driven.

[garymb]

Yes Gary, the limphome is plugged into the memcal which is plugged into the ECU which is then fitted with seals. The ECU is identical but the memcal determines which engine/setup it controls.

thanks Geoff. BTW I checked the connections-- at least the immediate connectors (the 2 blocks) and they seemed fine. Also left the battery disconnected for about an hour but it didn't re-set anything.

New ECU on the way tomorrow (at an inflated price it seems!) Still I hate being off the road in this weather and it's cheaper than the £400- odd I was expecting. Fingers crossed that it sorts the problem.

[RayD]

Is it worth trying the engine in service mode ( put the clip in while the engine is running) I wonder? Just to see how smoothly it runs, or not, and what revs it's doing.

Ray

Yup, I tried that-- it made no difference. The odd thing is that although it's idling very fast both (with the clip in and out) it's runny pretty smoothly-- no misfires, but very rich I think. The exhaust pops and bangs like mad if driven.

Gary,
In service mode it shouldn't be idling fast.
It needs adjusting to 950rpm. When the clip is removed it should stay the same.
Ray

[garymb]

New ECU fitted tonight and test driven. Problem appears to be sorted.

Geoff I have an old ECU for you to play with

Thanks all for your help.

[jon3929]

Am I glad to have read this conversation.........

I have a 1990 Elan which appears to have developed exactly the same fault this morning.

I started it up this morning, left it idling for about 5 minutes while I locked the house up etc etc, and shortly after pulling away the amber engine management warning light illuminated. I carried on, observed no symptoms, car drove quite normally. Then whilst queing in a bit of traffic it was idling high at 1500 rpm, shortly afterwards it cut out and wouldn't restart.

I scratched my head, thought about it, and couldn't see anything obvious. When the RAC pitched up we tried it again and it started without hesitation, although a very strong smell of petrol - quite obviously running very rich. With it idling again and jabbing the throttle quickly it was puffing black smoke and the light came on again very quickly.

I havent ever had any reason to investigate fault codes or much of the topics in discussion below, but, its all sounding very similar. I was thinking about ELanScan as a starting point, but I'm not so sure now......

What do you reckon? best course of action.......

Much appreciated, newbie Jon.