Unknown serious engine fault - PLEASE HELP

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Unknown serious engine fault - PLEASE HELP

Postby JossElan » Wed 29.03.2017, 08:18

My Lotus has an intermittent engine fault which is not registering a fault code (with the paperclip test). It usually starts with a small judder* followed by the engine light coming on, the judders will then become more frequent and then the engine will start running rough. If I continue, it will really start cutting and juddering and the engine will start cutting out when I lift off the accelerator. Can anyone help!? :cry:

*the initial judders feel like a half-second loss of power and I get corresponding lurch forward.
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Re: Unknown serious engine fault - PLEASE HELP

Postby JossElan » Wed 29.03.2017, 08:20

I should also point out that sometimes the light will go off and it will run fine for a bit; if I'm driving at a steady pace.
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Re: Unknown serious engine fault - PLEASE HELP

Postby rip » Wed 29.03.2017, 09:23

Hi,

CEL coming on but not giving a fault code is unusual.
It does not sound like a major issue though. I would call something mechanical major such as the engine not turning or a massive oil leak.
I suspect a CAS fault although at the moment there is not much to go on.
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Re: Unknown serious engine fault - PLEASE HELP

Postby Giniw » Wed 29.03.2017, 11:46

Hi, if there is no recorded fault code after the engine stops and the CEL was on, couldn't it be an electrical problem with the ECU being not properly energized?
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Re: Unknown serious engine fault - PLEASE HELP

Postby Rambo » Wed 29.03.2017, 15:03

This may be a red herring.......

...but what exhaust system do you have on your car ? And are you on full boost when this juddering, lurching forward or power loss takes place ?

Just a thought :?
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Re: Unknown serious engine fault - PLEASE HELP

Postby clemo » Wed 29.03.2017, 17:33

Giniw wrote:Hi, if there is no recorded fault code after the engine stops and the CEL was on, couldn't it be an electrical problem with the ECU being not properly energized?



my guess too
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Re: Unknown serious engine fault - PLEASE HELP

Postby JossElan » Wed 29.03.2017, 17:46

Hi all,

Thanks for your replies so far. I've just had the exhaust changed. It was a Lotus original and is now a PNG Sports Exhaust; however, the fault has been present with both.
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Re: Unknown serious engine fault - PLEASE HELP

Postby Brit-Car-Nut » Wed 29.03.2017, 18:26

With no details or fault codes, I think you will waste less time and money if you take it to one of the M100 specialists for diagnosis.

The possible list of causes is quite long and without some understanding of the M100, you will most likely end up replacing a lot of un-necessary parts trying to figure it out yourself.

Then again, maybe you like a real challenge or funds tighter as mine...
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Re: Unknown serious engine fault - PLEASE HELP

Postby Rambo » Wed 29.03.2017, 18:33

Brit-Car-Nut wrote:With no details or fault codes, I think you will waste less time and money if you take it to one of the M100 specialists for diagnosis.

The possible list of causes is quite long and without some understanding of the M100, you will most likely end up replacing a lot of un-necessary parts trying to figure it out yourself.

Then again, maybe you like a real challenge or funds tighter as mine...


And if you go down this route you will need to update your location in your profile. Because without knowing if you live at Lands End or John o Groats we can't recommend your nearest M100 specialist or knowledgeable LEC M100 owner
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Re: Unknown serious engine fault - PLEASE HELP

Postby JossElan » Wed 29.03.2017, 20:43

Profile updated. I'm in between Marlow and Henley, Bucks.

Well, actually, right now I'm by the side of the road waiting for the RAC after trying to limp her home!!!!
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Re: Unknown serious engine fault - PLEASE HELP

Postby JossElan » Thu 30.03.2017, 08:32

I think its time for a specialist to have a look - Any opinions on Hofmann's in Henley, Steve Williams in Maidenhead or SGT in Taplow?
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Re: Unknown serious engine fault - PLEASE HELP

Postby Simon_P » Thu 30.03.2017, 10:04

First do some free diagnosis yourself

Check battery terminal connections
Check engine earth - wire and croc clips from the braid on the chassis to the plenum
Check CAS is tight and hasn't slipped.

Is it ok when cold ? and then deteriorates when hot
Only happens under load?
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Re: Unknown serious engine fault - PLEASE HELP

Postby JossElan » Thu 30.03.2017, 12:06

Thanks Simon,

I'll have a look at these tonight.

Simon_P wrote:Is it ok when cold ? and then deteriorates when hot
Only happens under load?


It tends to begin after a couple of minutes, usually after applying load but not full boost, and then develops to full cutting-out over the next 5-10 mins; however, sometimes the light will go off again and I can drive for extended periods - although by this stage I'm nursing the car and diving as steadily as possible; keeping the revs below ~3k. After I broke-down last night it would start but then cut-out after 1-2 seconds; however, I waited for an hour and then it started fine and I drove the rest of the way home (very gingerly!).
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Re: Unknown serious engine fault - PLEASE HELP

Postby Danevansgolf » Sun 02.04.2017, 09:10

If I was you i would either change the spark plugs or when the engine is hot, take the plugs out and see if there are any cracks on the ceramic parts. Plugs only cost a tenner. I've had a similar problem, which turned out to be the plugs, which had hairline cracks in them. Only found them when I took them out hot, and the cracks were visable. Good luck
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Re: Unknown serious engine fault - PLEASE HELP

Postby JossElan » Fri 21.04.2017, 00:45

Update: Just taken it to my new local specialist (SGT, Taplow). They struggled to get the car to communicate with the Élan scan but finally got a Code 34 - MAP sensor fault. They've ordered a replacement (~£200) and I'll provide an other update when it's been fitted.

Thanks for all your advice
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Re: Unknown serious engine fault - PLEASE HELP

Postby muley » Fri 21.04.2017, 08:17

Pleased to hear that progress has been made.

£200 seems a bit steep, IIRC I paid about £20 for mine. Listed as for a VOLVO something or other.


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Re: Unknown serious engine fault - PLEASE HELP

Postby Brit-Car-Nut » Fri 21.04.2017, 14:02

The MAP sensor is a standard 2BAR unit used in a lot of cars, mostly GM influenced. The most common aftermarket part number is Standard Motor Products AS4. Prices vary wildly but it is most important to make sure you are getting the 2BAR version as there is a 1BAR part that basically looks the same and the electrical connection will work. The best way I found to be sure is to make sure the connection area key is RED/Orange in color.

I found some on eBay for $15.00 a while back.

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Re: Unknown serious engine fault - PLEASE HELP

Postby muley » Fri 21.04.2017, 17:30

JossElan wrote:Update: Just taken it to my new local specialist (SGT, Taplow). They struggled to get the car to communicate with the Élan scan but finally got a Code 34 - MAP sensor fault. They've ordered a replacement (~£200) and I'll provide an other update when it's been fitted.

Thanks for all your advice


FWIW, they didn't need to struggle with Elanscan, they could have used a paperclip.


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Re: Unknown serious engine fault - PLEASE HELP

Postby JossElan » Tue 25.04.2017, 01:01

The paper clip test wasn't generating a fault and even the Élanscan took a few attempts to connect. More importantly, I've been done up like a right kipper!!! They ended up charging me over £400! Don't think I'll be taking my car back there again. There was another (red) Élan there too, apparently with the same problem. Wonder if they got shafted too!
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Re: Unknown serious engine fault - PLEASE HELP

Postby clemo » Tue 25.04.2017, 09:13

JossElan wrote:The paper clip test wasn't generating a fault and even the Élanscan took a few attempts to connect. More importantly, I've been done up like a right kipper!!! They ended up charging me over £400! Don't think I'll be taking my car back there again. There was another (red) Élan there too, apparently with the same problem. Wonder if they got shafted too!



Well the good news is you are back on the road .
If you initial diagnostic of unknown serious engine fault had have been the case then you could have been thousands down .

SGT though ... one to remember (or forget)
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