engine rpm lowering and/or stopping

[Pascal]

Hello ,

i already received some answers to my problem (through other topics) and I thank you all for that.
The difficulty is that the answers are pointing out different possible pain sources (not surprising) , and investigations are wide.

Here is the trouble :
When arriving at - for instance a stop signal - i lower speed and i declutch , then the idle decreases to 500 rpm or less, and sometimes engine stops.
It is really dangerous when i want to go again after the stop - simply beeing stuck in the middle of the crossroad with engine off.

Reading the LEC wiki and forum, i see several informations about the MAP , and the coolant temp sensor ... HJ2 (many thanks to you ! ) suggests also a possible air bubble in the cooling system.

my Elanscan says there is something wrong with MAP High, but i don't know the meaning ( there is a fault , value 4096, constant) .
Manifold pressure is measuring values (0,2 ...0,8 ...) , so it should not be a faulty sensor - and anyway i changed this sensor 2 weeks ago, with no result, no change.

The car is just out of a LOTUS SERVICE France and they did not see anything wrong.

Brit-Car-Nut says it could be a "bad fuel pressure regulator' ( special thank to you also !) , when others say it may be a vacuum leakage ...

so i am lost and search soemone who had the same trouble.

I join an ElanScan if someone has time to spend on it.
- on one log, we see the rpm lowering (car stopped) ,
- on the other one the engine stops when i am driving and just changing gear !!!
note that some info are missing on the logs because the speedmeter cable is out at the moment (this is another issue).

hopefully see some of you in YLD Ypres, (If M100 doesn't run, i come by bicycle with a Lotus sticker on, but i come !!!)
Pascal - France

[wayne]

Hi Pascal.

It could be a long shot...... I've not read your other posts and was unable to read the attached log file

I've recently been having problems similar. It started as RPM would drop really low when slowing down as you mentioned
and the engine would cut out. Sometimes the car would re start immediately other times maybe after several minuets.

The starter would crank over normally. Eventually I noticed that the instrument warning lights seemed a little dim and
before it cut out fuel gauge would slowly move towards empty. If I kept the revs high the car would run.

It turned out to be a bad connection on 1 of the 2 earth wires at the battery.
Connections now cleaned and re secured... Been running fine for the last few weeks

This may not be of help and you may have already tried it. but if not it would only take you 5 mins to take off the wires and clean them up

Regards

Wayne

[Pascal]

hello,
Checking the battery connection is something easy i am going to do immediateley, with few hope, as i did that some monthes ago already and it was before the problems, and i never see any light or jauge dim.

I have cleaned the CTS connexion this morning (it was good).
If the CTS is damaged, i would have bad informations on the ElanScan i guess ? I have proper informations ( temp increases, then fans switch on at 110°, then lowering at 82 °C ...)

i just come from a new 'test trip', seems to be worse and worse. Engine stops when hot, when lowering to idle.
The car 'farts' more and more under 2000 rpm.
i have a bit of black soot at exhaust that i did not have before.
Those two things are worrying me.

The engine at idle makes (to my ear) a good sound. if hot ( 80- 100 °C) just after a run , but it is sometimes not regular.

Otherwise , running on the engine when cold is perfect, and driving at higher than 2000 rpm is perfect.

The ElanScan shows that after a run , rpm decreases to 575 rpm and come back to idle or stops.

Thanks for any idea,
Pascal - France

[HJ2]

Hi pascal,


The sensor that switches the fan is not the same as the sensor that feeds the ECU!
Check the WIKI to find out which does what (both on the thermostat housing)

[Pascal]

Hello ...
HJ2 ... done.
the switch of the fans is a 'one wire", the sensor is more difficult to acceed to. it has two wires and a waterproof plug .
i have cleaned both, following the wiki advice.

Note, about the wiki : It is possible to clean this sensor plug without dismantling the CAS.
the sensor plug is secured by a 'plastic hook', , i curved a 1 mm steel wire to pull this hook, and opened it easily (if someone interested, i'll describe more).
It was clear Inside, but of course i took opportunity to clean a bit more, using 'contact pilot' and cotton swab. No change.

investigations continue ... Many thanks,
Pascal

[wayne]

Sorry that the earth problem did not help you Pascal. ( Thought it was a slim chance but worth mentioning as it has taken me longer than I would care to admit to finding the cause of my problem).

A bad CTS would defiantly give a lot of black soot in the exhaust fumes. I replaced mine when I first got my car. But it was showing a CEL light code 15? IIRC.

After ordering a new one from Isuzu. Upon further investigation It was just bad contacts. I ran a small bead of solder along the contacts and it cured the problem.

I still replaced it as the top plastic part was cracked. I think I kept the old one. I'll have a dig around for it later (just finished work and am off to bed)!
If I can find the old one. I would be happy to send It over to you if you pm me your adress. At least it would help you confirm or eliminate this as the problem.

Removing the CAS gives a lot more access and it is just 1 bolt to remove. If you do not want to reset the timing mark the position with a felt pen so as to align it in the same position.

To remove the CTS I purchased a set of deep sockets (sorry do not remember the correct size that fitted). You do not loose much coolant when you remove it).

[HJ2]

Did you also remove the temp. sensor from the housing and clean the thread? (the sensor ground so to say)
Still, the Elansan report would make me look in the MAP direction as it reports 'constant high'

[Pascal]

Hello,

i have taken the MAP sensor out (not easy to do that ! ) , all its hoses out, also the plug elbow, , open the elec plugs and improved contact... , and the 'MAP High' message has now dissapeared !

I also took out the Brown sensor on the left side, cleaned hose and contacts ...

HJ2 you were likely right from the beginning ( and i have to speak to Lotus service who charged me 230 euros to do that job two weeks ago ...).

but the problem has not changed ! i loose the idle and still have the engine stop. Now, i had the yellow light "on" two times , one minute lasting, after boost ride.
My ElanScan now says " fault : 1 " and it is "VSS" (first one in the list) , what is this VSS ? didn't find yet "VSS" in forum or wiki.

At least happy to make a step forward.

Regards,
Pascal

[HJ2]

Variable Speed Sensor perhaps?
I believe it is in the dashboard, taken from the speedo. Perhaps a bad grounding / contact?

[Pascal]

Hummm ...

I have a speedo problem ... if 'VSS' is taking an information at the dashboard speedo and sends it to ecu, then this could create the problem.

can you or someone confirm what means " VSS fault '' ?

At low speed, when i read 50 at the speedo, my GPS says 35 km/h and the needle vibrates a lot.
When reading 70 at the speedo, GPS says 60 and needle does not vibrate anymore.

Faster : always + 10 km/h. I can survive with this if it doesn't bother the ecu.

Pascal J-4

[HJ2]

The offset between speedo and gps is normal
The bouncing speedo is your problem mate!

I believe i had the same problem a while ago, but cannot remember...
I adjusted the speedo cable at the gearbox end (see wiki) and found a problem at the dashboard end, making the cable slip. Adjustment cured it, a time consuming but pretty straight foreward job.

While you are in there under the dash, check grounding of instruments as well!

Looks like you can make it to Ieper after all.
Goodluck!

[Pascal]

Hello,

M100 seems to work better now ( no MAP problem anymore !) but still farting/ poping a lot at 1500/2000 rpm.
More and more i would say.

Some smoke ... I called my local experienced mechanics, he changed his schedule to help me and M100 is in his hands this evening and tomorrow.

He told me he was a bit anxious about my valves... this may be a serious issue.

Till now , i have read on the forum that we have a strong and reliable engine , i don't know about the valves.
Smoke, poping , timing loosing ... does it smell bad ? Some experience about this ?


I shall be in YLD anyway, eventually painting by hand my 4x4 Mazda in English green and yellow !

Pascal France.

[HJ2]

Haha!
A painted elan, that would be a first...

I don't believe it has anything to do with your valves. You would hear it immidiately. Don't spend mony taking the engine apart my friend!

Do you still have engine warning light?
Also i would start with setting the base timing as per wiki!!!

[HJ2]

Do you have an O2 sensor?

[Pascal]

I would say no O2 sensor (i cannot look, the car is not here this evening but ...) :

- it is a 1991 model, it seems according to wiki that this sensor came later.
- reading my service manual of 1991, i see no reference to an 'O2 or 'oxygen sensor.

my mechanics says i have a crack in the exhaust pipe he is going to weld (first elbow) , not sure this can be the cause of the trouble but at least it doesn't help.

Pascal

[Brit-Car-Nut]

Maybe the mechanic also meant valve timing, not the physical valves?

[Gazza]

I had similar problem. Stick it in service mode and adjust the revs to 800-1000 under the bonnet.
In service mode mine was only 400-500 but ticked over at 900 and cut out when stopping.

Gazza

[Pascal]

Hello,

one additional information, my mechanics told me that a common fault is due to a small motor or actuator that controls the idle (the air intake valve) , i search for the exact name of this part in the wiki and manual.
Maybe ' secondary throttle vacuum actuator' ??? He showed me a spare (from an Audi) , it looks like a small motor with a shaft to push the valve.
He says that it is anyway wise to replace it after 22 years on any cars so i search for a cross reference, do you know ?

Otherwise, welding the crack of the exhaust seems to improve the smoothness of the engine and decreases poping.

base timing not yet adjusted. it seems to be a bit messy to do it for a non mechanics ???


I shall test more tonight.

Pascal

[HJ2]

As stated before, start with base timing, as this is your reference for everyting.
It is not messy, but very easy, and is described vert thouroghly in the wiki

Good luck.

[Gazza]

Try what i said first. I had this problem for ages until someone told me. Do a search for rev idle or similar. Real easy to do. My car ticked over at the usual 1000rpm but slowing down or stopping the car would just cut out because the revs used to drop rapidly.
In service the tick over was all over the place as low as 400. Simply adjust them by the screw, take it out of service mode a tick over was same as before but didn't drop when braking.
Think Ray D was the man who helped me by posting and has posted it a few times since