1984 Esprit - Very poor acceleration HELP!

[ckalkhof]

Thanks for taking the time to look at my post. I have had my lotus (1984 model)for about a year now and have done the following:
1. Replaced the cracked wastegate adaptor with a new one (ouch).
2. Rebuilt the turbo
3. Full service (all belts, hoses,tuneup etc....)
4. Rebuilt the wastegate.
5. A ton of other stuff
The car has only 25K miles and still has one nagging problem (before and after the service):

Whenever I accelerate (either from 55mph or a dead stop) the car bogs down (stumbles)terribly and almost stalls. If I keep the revs up and slip the clutch I can get away smoothly. Some people have told me that this is related to the accelerator pump on the carbs? The carbs have never been rebuilt. Are there any tests that I could perform to confirm or deny the justification of a carb rebuild.

Again, thanks for taking the time out to give me a helping hand. I hope in the future, that I will be able to contribute to this forum with some of the things that I learned while working on my Esprit!

[lotusguy]

Thanks for taking the time to look at my post. I have had my lotus (1984 model)for about a year now and have done the following:
1. Replaced the cracked wastegate adaptor with a new one (ouch).
2. Rebuilt the turbo
3. Full service (all belts, hoses,tuneup etc....)
4. Rebuilt the wastegate.
5. A ton of other stuff
The car has only 25K miles and still has one nagging problem (before and after the service):

Whenever I accelerate (either from 55mph or a dead stop) the car bogs down (stumbles)terribly and almost stalls. If I keep the revs up and slip the clutch I can get away smoothly. Some people have told me that this is related to the accelerator pump on the carbs? The carbs have never been rebuilt. Are there any tests that I could perform to confirm or deny the justification of a carb rebuild.

Again, thanks for taking the time out to give me a helping hand. I hope in the future, that I will be able to contribute to this forum with some of the things that I learned while working on my Esprit!

Hi,

Sorry to hear of your trouble. Rebuilding the carbs may be the order of the day. But, don't overlook the simple stuff first.

1. Do a compression test. The resulting pressure is not necessarily as important as having all cylinders reading within a few PSI of each other.

2. Check to be sure fuel pump is in top working order and that you haven't got a fuel filter which is partially blocked.

3. Test fuel pressure regulator and associated vacuum hoses and vacuum solenoids for proper operation.

4. Check Carb Floats for proper height and weigh them to insure they are not leaking. 8gr. is the optimum weight.

5. Be sure that carbs are properly sealing with the intake manifold, that the rubber insulators (donuts) are not leaking (check for proper gap between carb spacers and manifold). Check that all plenum seals, vacuum lines are in good order.

6. Check to be sure that ignition timing has not been advanced too far. 28° is optimum, 30° max. After 30°, power drops off significantly.

7. Be sure that the proper air gap has been maintained between the stator and reluctor in the distributor.

8. Be sure valve timing is correct, if it has slipped a tooth, this could be the problem.

9. How good is your service history on the car? Have the Heads been milled? If so, 0.040" is the max. allowed to remain serviceable. After 0.040" has been removed, correct valve timing can no longer be established and the head must be replaced. (Extremely remote possibility, but I have seen it happen.

If, after checking all of the above the problem is not solved, then a carb rebuild is in order. Not a difficult job at all, about $125.00 in parts. Hope this helps. Happy Motoring! Jim'85TE

[maigret]

A useful tool for checking the carbs is the Gunson blue tune which is a glass top spark plug. Bought mine in the UK for less than 20GBP and discovered the accelerator pump wasn't 100% on the car I had at the time.
When correctly tuned the colour should be blue. Yellow indicates a rich mixture (remember the bunson burner from school?). When the accelerator pump is working correctly the colour should turn yellow when the pedal is stomped on and return to blue when held steady. If the flame becomes erratic or stays blue the the pump isn't working.
At the time the total cost of the repair was 15 GBP for the Blue tune and 5GBP for the part. Cheaper than getting a mechanic to look at it and I still have the BT 13 years later.

[lotusguy]

maigret said: A useful tool for checking the carbs is the Gunson blue tune which is a glass top spark plug. Bought mine in the UK for less than 20GBP and discovered the accelerator pump wasn't 100% on the car I had at the time.
When correctly tuned the colour should be blue. Yellow indicates a rich mixture (remember the bunson burner from school?). When the accelerator pump is working correctly the colour should turn yellow when the pedal is stomped on and return to blue when held steady. If the flame becomes erratic or stays blue the the pump isn't working.
At the time the total cost of the repair was 15 GBP for the Blue tune and 5GBP for the part. Cheaper than getting a mechanic to look at it and I still have the BT 13 years later.

Hi,

I also have the Gunsen 'ColorTune®' and have used it will good results (on other cars), but I would not recommend it for an Esprit owner.

The reasons for this are that the 'ColorTune®' is difficult to work with on the recessed head of the Esprit as well as the tool's inherent inaccuracy. Also, it does not do a particularly good job of tuning and balancing multiple carbs.

Because it is pretty dim, it's color can only be accurately gauged in a relatively dark space, and operating the car in such a confined space is unwise. Add to that the color determination is really very subjective and you can get spotty results.

The easiest and most accurate way to tune your carbs is to use a manometer such as the 'CarbTune II®' sold by EuroCarb in the UK. You can permanently mount the test ports on the carbs and cap them, such as I have done. Once this is done, carb tuning can be accurately accomplished in under 5 min.

This leads me to another possible cause in the problem you are experiencing, namely Carburettor. Balance.

On the Esprit, you essentially have one barrel of each carb dedicated to a single cylinder. If your carbs are not properly balanced, you can essentially be running on fewer than 4 cylinders. This may not seem the case, but a weak or improperly tuned barrel, can cause the cylinder it is assigned to to lag behind the others resulting in poor performance.

With a manometer, you first tune each barrel to it's counterpart on the same carb, and then, balance each carb to the other.

My advise, skip the 'ColorTune®' and apply the money saved to a manometer such as the 'CarbTune II®' (approx. $50-$60 shipped from the UK). You will have a more accurate and much more versatile tool. Happy Motoring! Jim'85TE