Help! Elan Turbo with bad cough

[newtonlad]

Hi All, my 1991 Elan turbo has been running fine for the last 5 years of ownership. It runs fine and ticks over OK, but when I take it for a run it starts misfiring, when warmed up, and cutting out when stopped at lights etc and it seems to be gradually getting worse. If I floor the accelerator it stutters for a few seconds and then revs like buggery! I have renewed the plugs, leads and coils in the last two years. The pleasure I had from driving it has evaporated, as it is an embarrassment to drive in traffic. Does anyone have any ideas where to start for an old man?? Thanks in advance.

[Dave Eds]

Does the engine management light come on? Any fault codes showing via the paperclip test? Can you smell fuel?

[newtonlad]

Hi Dave, yes, the orange engine light comes on when it cuts out, and there is no smell of fuel. I havent done the paper clip test yet, as I would have to get the car out of the garage, and storm ARWEN is raging outside at the moment.

[Rambo]

So what's stopping you? You can do the paperclip test in the garage

Code 41 or 33 ?

[lotusflasherman]

Hi Dave, yes, the orange engine light comes on when it cuts out, and there is no smell of fuel. I havent done the paper clip test yet, as I would have to get the car out of the garage, and storm ARWEN is raging outside at the moment.

I'm going from memory but I believe the Check Engine Light is always on with Ignition On and engine not running, it's part of the bulb check arrangement - somebody will have to check that for me because the battery is out of mine as it's been on SORN since the start of Covid, and I might be talking out of my .. err..."exhaust pipe" ..

[lotusflasherman]

If it runs OK when cold and then starts to play up when warmed up/hot it's possibly the Coolant Temperature Sensor. The CTS tells the ECM the engine temperature by being supplied with 5V from the ECM which monitors the voltage coming back from the thermistor and adjusts the fuel ratio accordingly. For a cold engine the thermistor has high resistance (8kΩ in iced water = 0°C) and low resistance when hot (185Ω in boiling water). When the CTS has failed it will have gone open circuit, so high resistance, and the ECM will continue fuelling for a cold engine even when it's warm.

The CTS is screwed into the thermostat housing which has 3 sensors. Rad Fan thermal switch is in the boss beside the top hose and towards the cam covers are the Temp Gauge Sender which has one wire, beside it is the CTS which has an oval connector and the 5V supply wire and the voltage signal wire. CTS is more difficult to get at but that's Sod's Law in action.

Because the CTS produces a range of resistance in normal service it will not always cause an Error Code or CEL light when it goes awry. (At cold the CTS and Mass Air Temperature Sensor are compared and if wildly different code 14 or 15 sent, but air temperature hardly changes on your journey, coolant temperature does.) It's worth checking the cold and then hot resistance with a multimeter before buying a new one. They are available from SJSportscars but you won't get much change from £100.

[Saltire]

If it runs OK when cold and then starts to play up when warmed up/hot it's possibly the Coolant Temperature Sensor. . . . if wildly different code 14 or 15 sent, but air temperature hardly changes on your journey, coolant temperature does.) It's worth checking the cold and then hot resistance with a multimeter before buying a new one. They are available from SJSportscars but you won't get much change from £100.

This happened to me recently. CEL went out on startup, but came on regularly after I’d covered about 4 miles, and there was a flat spot as big as the Nullarbor on acceleration. Paper clip switch (I have one in the glovebox permanently wired in) showed a 1-4 code. I managed to get a new CTS from Simon_P of this parish, and subsequently acquired a couple of spares just in case. They were much less than £100 each though.

The manual says to remove the cam angle sensor to reach and replace the CTS, but I managed to get at it with a wobble socket on the end of a long extension bar. If you replace it, DON’T overtighten; it’s a tapered thread and you’ll ruin it if you do.

Good luck!

[Rambo]

Did you manage to carry out the paper clip test yet newtonlad?

[KenS]

Can anyone confirm that a standard 'TX3' CTS (about £5 on ebay and £1.90 at Rockauto) is equivalent to the Lotus part? The Rockauto site gives equivalents to the TX3 as 12146312 and the resistance spec for that compares fairly well when considering the tolerances :

The Lotus spec from the Engine management manual:

CTS spec.JPG

Is this good enough?

size.JPG

spec.JPG

[muley]

..or this?
https://www.ebay.co.uk/itm/383582473736

[newtonlad]

Hi Guys, it never rains but it pours! went to take the car out of the garage only to find the battery was flat!! so, having disconnected it to charge it up overnight I understand I will have lost all the stored diagnostics. Started it up this morning, ticking over fine, until cooling fans cut in, {between half and threequarters on the temp. gauge} removed glove box ready, but I have to go to Bristol today, so checks will have to wait. I have sent an E-mail to there's only on f in Geof Smith to purchase an interface, but he hasn't replied. Thanks for all the useful info you have posted. There is definitely food for thought. I have looked at the position of the sender in the thermostat housing and my first thought was "what did the designer of this car have against mankind"? Like most men on the planet an extra 2 to 3 inches would have made all, the difference {to the car obviously for access}. Thanks again Tony.

[Rambo]

If you have a garage, invest in a CTEK battery conditioner, or something similar. Your battery will always be in tip to condition and ready go go. Money well spent.

If you don't use a battery conditioner beware that your battery will discharge enough over about 10-14 days to not start the engine. Particuarly important over these cold winter months to have the battery in good condition

[newtonlad]

Hi Guys, took the Elan out for a 28 mile run this morning, 1 degree C, and sods law it performed impeccably, no coughs or splutters! left it tick over on the drive until fans cut in, and then drove it again when hot, no problem. It's a head scratcher. Maybe leaving the glove box off helps.....! And no, I didn't disturb the ECU or associated wiring. I will have to wait until it plays up again. Ps. E5 petrol £1.59'9p a litre?? someone taking the urine or what??!! Thanks again to the gents who replied with fault remedy suggestions, much appreciated.

[MackieRM]

If it runs OK when cold and then starts to play up when warmed up/hot it's possibly the Coolant Temperature Sensor. The CTS tells the ECM the engine temperature by being supplied with 5V from the ECM which monitors the voltage coming back from the thermistor and adjusts the fuel ratio accordingly. For a cold engine the thermistor has high resistance (8kΩ in iced water = 0°C) and low resistance when hot (185Ω in boiling water). When the CTS has failed it will have gone open circuit, so high resistance, and the ECM will continue fuelling for a cold engine even when it's warm.

The CTS is screwed into the thermostat housing which has 3 sensors. Rad Fan thermal switch is in the boss beside the top hose and towards the cam covers are the Temp Gauge Sender which has one wire, beside it is the CTS which has an oval connector and the 5V supply wire and the voltage signal wire. CTS is more difficult to get at but that's Sod's Law in action.

Because the CTS produces a range of resistance in normal service it will not always cause an Error Code or CEL light when it goes awry. (At cold the CTS and Mass Air Temperature Sensor are compared and if wildly different code 14 or 15 sent, but air temperature hardly changes on your journey, coolant temperature does.) It's worth checking the cold and then hot resistance with a multimeter before buying a new one. They are available from SJSportscars but you won't get much change from £100.

My friend got this Elan with issues when warmed up. Hope it's just the coolant temp sensor. We'll check if it also throwing a code soon after we installed the suspension from 4Wheelonline onto the truck and cleared the garage.