Engine Check light on - Under Deceleration?

[igreenrover]

Hi Guys – I’m back again.


I have a “small” problem with my 89 SE.

I drove From Manchester to LeMans this weekend, and ‘cleverly?’ put some injector cleaner in the car before hand. After about 75 miles the Check Engine light started to come on when gently lifting off the accelerator and slowing slightly (at around 70mpm). After about 5 - 10 seconds the light goes out.

I filled up in France and then had no problems for the entire French side of the journey (350 miles). On return to the UK last night, it started again! I can’t see any obvious problems, all temperatures and pressures appear fine and no strange noises.

Any ideas,?
Does my Esprit no longer like the UK?

Thanks,
Gareth

[cnh1990]

Assuming that you have the Delco equiped SE. The fuel is drawn from right tank and connected to the left tank via a balancer line. When injector cleaner or sometimes gas stabilizer used it may confuse the sensors and the computer that regulate the fuel and ignition. Some people dump in cleaner into one tank and sometimes it does not mix well.

Run your fuel to near empty and fill with your normal brand of fuel. After you are fairly certain that most of the injector cleaner is gone, reset the computer by disconnecting the battery or pulling the fuse for a while.

I like to do it after the car is put away for the night or the first thing in the morning as the engine is cold.

Idle the car till the fans kick on. Then go for a drive. The computer will learn the the new fuel setting and after a 30-100 miles it should be back to normal. Also use the A/C once in while during the learn phase to make sure the idle is correct with the A/C on.

Good Luck,
Calvin

[igreenrover]

Thanks for that Calvin, I will be just about out of Fuel by weekend so will give it a try then.

Gareth

[cnh1990]

Also one other thing could be happening. Many years ago I vaugely remember a problem I had that gave a similar symptom.

If you have a fuel system that is leaking air, it could also cause a symptom very close to what you describe. A fuel cap left off, air leaks from hoses off the tank neck or the tank balancer line/charcoal canister line that is rotted apart. The Esprit has a closed fuel system and for some reason if it is running with the fuel system open I have seen such a problem with the check engine light with a error code of I think 24 which is VSS (vehicle speed sensor). I checked and tested the VSS and it was fine. As soon as I fixed the air leaks the problem went away.
Good Luck,
Calvin 90 SE

I suppose there is a possibility that your car no longer likes English fuel that has been taxed so much.






>> Edited by cnh1990 on Friday 20th June 14:09

[swedishsurgeon]

The check engine light glowing slightly around 70 mph has me wondering. There are two types of codes stored in the computer. The first being "soft" codes... these are trouble symptoms the computer sees and records them and the light will go out. It should keep a count every time the fault occurs. The second is a "hard" code... being a permmanent failure in the system. The light will stay on steady all of the time whilst driving. Anytime you get a check engine light, you should see what codes are stored before you erase them to know what is going on. Our practice is to read the codes, clear them and see if they come back and then we look into them should they return. If you short two terminals in the ALDL with a paper clip, you can get a "blink code" from the light but to do this you must know what terminals to connect. Spend a few quid and have it scanned, find out what the code is, write it down, and have it erased. I recall reading in my Lotus shop manual not to run certain things through the fuel system. Most injector cleaners will not hurt fuel systems, but they can freak out the O2 sensor. The method I learned to reset GM computer systems is to disconnect the negative terminal on the battery, hold the key to crank position for 10 seconds, turn the key back to off and reconnect the terminal.

Good luck,
Robert

EDIT: I forgot to mention that these chemicals can kill an O2 sensor.

>> Edited by swedishsurgeon on Sunday 22 June 03:53

[igreenrover]

Well. The engine check light persisted in coming on randomly - 100 miles nothing, then back again. So I had a look at the stored fault codes, it listed the following!

1. VSS Sensor
2. Throttle position sensor
3. MAP Sensor

Is it likely for these to all develop at the same time? Prior to 4 weeks ago the light had never been on. Is there any easy way for me to check these?

(I couldn’t find any fuel system leaks although a vacuum leak appears to have developed around the interior heating system).

Thanks & ??

[cnh1990]

Check the charcoal canister connections. You may have to remove the tank cover to see if the hoses are rotted away or to check the condition of the check valve under the right hatch gutter.
Calvin 90 SE

[Robert87hci]

A bad MAP sensor could trigger the Vehicle Speed Sensor
{VSS} and the throttle body position switch. You would need to tap into the computer with a scan tool and read the parameters of the sensors. In the trade, I've replaced more MAP sensors than TPS and VSS componets.
Check the vacuum line at the MAP sensor. Does the other end of the vacuum line from the MAP sensor go to a ported vacuum switch? This switch screws into a coolant passage and usually has three vacuum ports. Since my car is a CIS system, I don't have any of that,
and basing my thoughts on similar systems I have seen.
Do you have the OE repair manual? It may help however when I have a problem, it's never listed!
Good luck,
Robert