Fault code 41 left after clearing 33, 41, 42 and 54

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Fault code 41 left after clearing 33, 41, 42 and 54

Postby C3LOS » Fri 28.04.2017, 19:49

As I brought my car out for the season, I noticed on WOT that I am getting an intermittent misfire/stumble....roughly around 4000rpm in second or third gear. What I mean by intermittent I mean once or twice in a 30 mile run. The engine light tends to come on and off but have always thought that is the air fuel sensor inherent issue all leans have.
Checking for codes got 33, 41, 42, and 54.
I cleared them and rechecked and all was clear. I then ran the car at idle instantly getting an engine warning lamp.
So rechecked for codes and got 41.
I recently had the head skimmed and a new cam belt fitted (by Paul Matty sports cars) and have done around 500 years.
Have checked around the edge bay for anything obvious but all looks good.(note my car is a 92 SE without an O2 sensor)
I have seen a few threads on chipping the ECU, but have no idea how to check for this, but as far as I know it isn't chipped, plus others have mentioned plug gaps, running higher octane fuel, or even cracked spark plugs.
Any thoughts on where I should go next?
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Re: Fault code 41 left after clearing 33, 41, 42 and 54

Postby Simon_P » Fri 28.04.2017, 21:05

I had the same thing about 490 years ago.

Most likely Code 41 and an intermittent stumble is the HES giving up. At some point the light will come on permanently and you will be in limp home mode (max 4000 rpm)

Its an old problem and consequently the write-up is in the depths of LEC from another era.
See here http://www.lotuselancentral.com/repair/cas.htm

There is a relatively cheap HES replacement kit available from Lotus the instructions for which are in the Wiki under Cam Angle Sensor.

You will see from the write-up that the new HES has a flying lead so you will be able to tell if you have the original fixed HES or the newer version by looking at the CAS.
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Re: Fault code 41 left after clearing 33, 41, 42 and 54

Postby C3LOS » Fri 28.04.2017, 22:22

Thanks! Good we'll be the root cause of the problem.
Would this be the cause of the other codes too?
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Re: Fault code 41 left after clearing 33, 41, 42 and 54

Postby Simon_P » Sat 29.04.2017, 06:34

Often one fault code will cause another. 41 and 42 often go together.

The question is what actually caused them. Since the head has been off it could be any number of things.

Check the plug connections. And check the earth 2 groups screwed to the O/S end of the plenum.

After that it is down to maintainance how old are the HT leads? Plugs, etc As you mention someone found a cracked plug caused codes another found a corroded HT lead end.

Next unplug the battery to reset the ecu. Then check the Base timing and set the Idle (follow the correct method)

Now you have a baseline, drive the car to see if you get any codes. Chances are not, but if you get 41 and the HES socket is on the CAS rather than a lead the probability of HES failure is high.

One of GeoffSmith's interface cables will allow you, or someone here to read the ECU with Elanscan.
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Re: Fault code 41 left after clearing 33, 41, 42 and 54

Postby C3LOS » Sat 29.04.2017, 09:07

Simon, thanks for the info.
Have checked earthing and plugs, all looks good the the leads are old.
Have reset the ecu, filled it with high octane fuel this morning and took it for a drive and code 41 is still there.
In fact the engine light is now tending to be on more times than not.
Checked the Hall sensor and it is the old one, so looking like that's the culprit.
Will let you know when it's been swapped out
Thanks for your help
Carl
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Re: Fault code 41 left after clearing 33, 41, 42 and 54

Postby C3LOS » Fri 19.05.2017, 22:45

Finally got the sensor replaced and she is running like a dream! Though broke 2 of the 3 bolts when trying to remove the CAS cap. Bugger! After 25 years they had welded themselves to the aluminium casting!
Thanks for all the help resolving the problem!
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