Also search the forum for "stumble" i saw several threads only a few for your years but they all seemed to point toward fuel related issues, pumps and injectors.
you might try resetting the ECU by disconnecting the battery for a while.
Ditto on the stumble!! You can smooth out the stumble a bit by swapping out the cam gear on the auxiliary side and buying the green dot pulley. Contact your local serviceman if you are not so inclined. Ralph at RS Motorsports in NJ did mine, and it was a nice upgrade. Also...I believe you need do something with the throttle jack solenoid and the EBPV (exhaust back pressure valve). Plugging up one, and disconnecting the other. Just having a brain fart right now on which is which..
Also....go on the Esprit Fact File site ( non Flash version ) and find your way into the index area. You will then be able to pull up a wide array of information regarding the Esprit. Expand and read the “Components” and “Troubleshooting” sub categories.
Here is an excerpt taken from the index and may give you insight into your issue.
”Why does my Esprit engine rev so high when I cold start it?”
Many people panic the first time they start certain 4-cylinder Esprits with the engine cold. Usually (but not always ) the RPMs climb rapidly to 2,500 or higher. Relax. This is normal behavior. In order to meet federal emissions regulations, the Esprit engine management system contains two components called the Exhaust Back Pressure Valve (EBPV) and the Throttle Jacking Capsule. The purpose of these two items is to bring the catalytic converter up to operating temperature as quickly as possible. This is done because converters don't work well at removing pollutants from exhaust gasses until they are warmed up.
In the simplest terms, this is what occurs: When the engine is being cold-started, the engine management computer (ECM) sends a command that closes the EBPV. This valve is located within the exhaust pipe, at the union between the rear of the catalytic converter and the pipe going to the muffler (silencer). Closing this valve essentially blocks the exhaust, trapping heat which causes the converter to warm up more quickly. While the EBPV is closed the ECM is referred to as running in "open loop mode".
The problem with closing the EBPV is that it has a tendency to cause the engine to stall. If you have seen the movie Beverly Hills Cop, you undoubtedly have heard of the "banana in the tailpipe trick". In order to prevent the engine from stalling, the ECM also sends a command to the Throttle Jacking Capsule which causes the throttle plates to open up (similar to pressing the accelerator pedal). This causes the RPMs to rise and prevents the engine from choking itself. Note You can force the ECM to drop the idle by quickly and briefly stabbing the accelerator pedal at least halfway.
After approximately 2 minutes, the ECM switches to "closed loop mode". It sends the opposite command to the EBPV to force it to open, and tells the Throttle Jacking Capsule to stop holding the throttle open.
The problem with the whole concept of EBPV / Throttle Jacking mechanism is that if you attempt to drive during this warm up cycle, the car will perform like crap because the exhaust is blocked. Furthermore, because the EBPV is spring-loaded to remain normally closed, any failure in the system (like a disconnected vacuum line) will cause the car to drive terribly. Due to this, many Esprit owners have chosen to wire EBPV to remain constantly open, or have removed the valve altogether. To help prevent the annoying high RPMs (which are much louder once the EBPV is wired open), many have also removed or disconnected the Throttle Jacking Capsule. There is nothing wrong with doing this. Remember, this mechanism is only there because Lotus needed it to meet EPA laws in the USA. In fact, when Lotus built the Esprit GT3, it also removed both these components. They were able to do this because the GT3 was never intended for the USA market. Besides, removing these items also reduces vehicle weight which is part of the Lotus religion.
Refer to Technical Service Bulletin #3 for more info on this topic.
Also....here is a link to the green dot pulley....
Hope this helps
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