Lotus Esprit S4, British Racing Green


My favorite car in my favorite color. Having owned it now for over 17 years, I encountered some minor issues over the years. If you also own an Esprit, I hope the information on this site helps you out.

As with all older cars, components will fail sooner or later. To aid in tracking down issues related to the engine management, ABS and SIR, I wrote a program (Espritmon) to retrieve information from the computers involved.

If you do not own the official testing equipment (i.e. a Tech 1 scanner with the appropriate ECM, ABS and SIR cardridges), Espritmon may be of use to track down the cause of a particular issue.

Drive carefully! 




Basic data

Model:                         S4

Year:                           1994

Colour:                        British Racing Green

Interior colour:            Tan

Upgrades / modifications:


Problems and solutions:




Email:                          ESPRIT@UAV.NL


Protecting my Esprit

My car was keyed twice, and from the second time I have AVI footage from my webcam (perhaps I will put it on this website in the future, but it makes Lotus owners rather aggressive when they see this footage). I was also considering a bomb-free shelter as a garage. However, when the other owner (F16) came back, I had to move.


Real-time engine data and performance monitoring capability

In December 2008 I decided to write a program to monitor the various engine parameters in real-time. I installed a DELL mini-inspiron in the car to plot and log the data.

The screendump below shows the basic screen layout. The current version is V6.3. The screen below is the main screen.




Translating the contents of the 3 fault-words into the error codes can be done by pressing the ERRORS button:



And to track down the possible cause of a ‘code 26’ error, the menu allows each of the solenoids to be switched on and off separately.



[Back to Top]

Delco Moraine Powermaster IIIA ABS status display

The ability to interrogate the ABS control unit (Delco-Moraine) can be toggled with the ABS button.



The hold and release solenoids can be activated using the buttons in the control panel.


[Back to Top]

DERM / SIR status display

And if you have problems with your airbag computer, Espritmon does decode the error codes (use the SIR button).


[Back to Top]

Espritmon download

For those Esprit owners that would like to try the current version of the software, here is a link, but DO READ the manual.doc before running the software.

And, be warned, I did not plan to write USER FRIENDLY software, I just needed a real-time monitor for some of the data and a basic replay capability.




If you think it is useful, consider mounting a small laptop to the roof with the display visible while driving (your display is now upside down). Start the software and hit the ‘c’ key. Now the display flips and you have an Engine Indication and Crew Alerting System in your Esprit ;-)

The picture below shows an early setup of the mini-laptop



[Back to Top]

BOV and SS clutch hose

Had these installed at van Sten Engineering http://www.vansten.nl/

Chip #3 from P.U.K. Esprit Racing

Bought it at: http://freudhoefer.de/lotus/esprit/

Performed the install myself, makes indeed a big difference. Glad I bought this one.

!! However !!

Since running this chip I noticed that the long-term corrections performed by the ECM using the BLM cells became significantly larger (especially cells 6 and 10, representing the RPM range between 2800 and 3600 and the pressure range from 0.8 to 1.2 bar). When analyzing the VE tables, I noticed a significant difference between the original VE table and the one in chip #3. Since chip #3 is derived from the S4s chip and the S4s engine has a slightly different design, it may well be that for the S4s the volumetric efficiency is indeed higher in that particular range, but this is not the case with the S4. I restored the VE table in chip #3 to the standard S4 one and now the BLM corrections are within the normal range again. 

Electric Chargecooler Pump from WCEngineering

Since my car had over 77000 km, the maintenance documents did not show that the impellor was ever replaced, I knew it hadn’t been for the last 43000 km, and reading the stories of various Esprit owners I decided that mine was probably close to the end of its life. Also, having seen how some disintegrated impellors looked, I wasn’t looking forward to having pieces of impellor in my chargecooler circuit. I bought the pump at: http://www.wcengineering.com/index.html

Performed the install myself, quite a job to get the mechanical one out. Since my S4 has a revised wiring harness I tapped into the relay box at the fuel pump relay. Oh yes, the pump I removed looked like this:

As can be seen, the impellor was still fully intact!

[Back to Top]

Larini Exhaust

Had this one installed at van Sten Engineering. Makes an enormous difference, especially since the previous exhaust may have been a bit clogged with pieces of the catalytic converter.

RS232 interface on ALDL (to hookup Palm 3 or laptop)

Built it from one of the schematics I found on the web and installed it in the car with an RS232 connector. This makes it easy to hookup the cradle of my Palm to read the basic data. Modified an existing RS232 application (for logging GPS data) into a simple mode 0 decoder (still need to add the other modes). The following picture shows the setup before being tucked away under the passenger console.

[Back to Top]

Tilt sensor

In the Lotus Esprit manual, the description of the Trouble & Alarm codes indicates that code 33 signals that the alarm is activated through the tailgate switch, and that it uses terminal 16 on the ECU as the connection to the switch. Also, code 32 would signal the opening of the bonnet, the switch of which is connected to terminal 4 of the ECU. When comparing this to the schematics (sheet 25), there appears to be an inconsistency. The bonnet switch is connected in parallel to the door switches and all go to terminal 3 of the ECU. Terminal 4 is used by the tailgate and terminal 16 is not used. After opening up the alarm ECU, it appeared that terminal 16 is connected using a pull-up resistor, but there is no wire on the contra connector. So, there is at least one free input to the alarm system! I acquired a tilt-sensor and hooked it up to terminal 16. It works!

New VDO speedometer

In June 2007 I installed a new VDO speedometer. For the S4, the number of pulses per km that needs to be used for correct calibration is 4000. The scaling on the new speedo is a bit awkward, with digits every 30 km/h and tickmarks every 5 km/h it is harder to read than the previous one (digits every 20 km/h and tickmarks every 10 km/h). Also the filtering applied seems to have a rather long time-constant so when decelerating to a certain speed it is much easier to use the digital readout (in which I do not filter the speed).

[Back to Top]

Bluetooth interface

To get rid of the cable between the laptop and the ALDL-RS232 interface I installed a RS232-Bluetooth adapter (Brainboxes BL-830). Now I will be able to use other PDA’s (no longer the old Palm III) that do not have an RS232 interface.

Digital Turbo Boost Indicator and Quad driver monitor

Recently build a digital turbo boost indicator using an absolute pressure sensor and an Atmel ATTiny 26 processor. Also added an interface to show the output state of the two quad-drivers of the ECM (had been experiencing some code 26 warnings). Installed the display and the LEDs in an aluminum panel.


[Back to Top]

Problems and solutions

Headlight pods

Some evening, while the car was parked, it suddenly began to raise the headlight pods in a stepwise fashion, making a tac-tac-tac sound.

As a quick fix, I removed the pod delay module and installed a jumper which maintains all functions except the pod delay (see picture). So, the pods raise when you switch the light on, put do no raise when you just briefly flash.


It turned out that one of the two SMD transistors in the pod delay module allowed a small current to leak through (after a couple of hours) which continued to increase. This charged the capacitor and caused the relay to engage (after some more hours). After having replaced the SMD transistor with a normal one (didn’t have the SMD part), the pod delay module worked ok again.

The failed SMD transistor in the pod delay module, until now the smallest part that failed in my Esprit.


[Back to Top]

Failure of speedometer

On one of the hottest days this summer the needle of the speedometer suddenly started jumping around. So I had to remove the instrument panel.


After having opened up the speedometer it appeared that the ring with the magnet that is connected to the rotating shaft had slipped about 1.5 mm, providing a bit of play and making contact with the axis on which the needle is connected. After having locked the ring in the right place, the speedometer worked ok again.

Meanwhile I noticed that in my S4, the orange-brown wire from pin 8 at J2 of the ECM runs all the way to the binnacle, so should a replacement with an electronic one be needed, it should be a straightforward install.


[Back to Top]

Alarm not functioning

When I bought the car, the previous owner (3rd owner) did not know it had an alarm (standard on the S4 as far as I know). It appeared that the 2nd or 1st owner had a remote door opening device installed, but had this directly connected to the motors controlling the locking mechanism (so not using the existing CDL, which was no longer present in the car). After having acquired a CDL module and bringing back the system in its original state, the alarm worked again. After figuring out how the remote door opening system worked (WAECO MT350) I integrated it with the CDL, so now everything works together.


[Back to Top]

Cat stuff in the exhaust

The car didn’t run very well, it lacked performance and it got worse and worse. These are some of the pieces that we found after disconnection the exhaust from the Cat.

Amazingly, with what is left of the Cat it still passes the MOT requirements!


[Back to Top]

Fuel leak

A strong smell of fuel in the cabin and after inspection I noticed it dripping onto the engine. The O-ring turned out to be the culprit


[Back to Top]

Secondary injectors suddenly active

Recently, the Esprit started running very poorly. It turned out that sometimes the secondary injectors became active without the ECU commanding them.

Currently solved by disconnecting one secondary injector, still need to figure out the real cause (already replaced injectors, cable, ECU).


[Back to Top]

2010: sandblasting of links, new bushes, recored radiator, new springs and dampers

Some of the parts after sandblasting and recoating


Rear suspension with the new springs and dampers                                      Front suspension


[Back to Top]

HiSpec 6 pot calipers and 32cm front discs

Installation of the new brakes (kit from PNM Engineering)


Looks better than the previous ones!


[Back to Top]

Brembo calipers and 30.4cm rear discs


[Back to Top]