Unleaded Problems!!!!!

[andybharris]

I have a 1988 maestro 1.6l AUTO running on an s series engine 69000mls. The previous owner had fitted a new timing belt (not sure if the timing is out)
The problem i have is that the engine runs very very hot yet the guage only ever reads a quarter unless i am stationary then it reads half. when i turn the engine off it continues to run for a couple of seconds and makes a terrible fracas under the bonnet.
The problem is worse when using unleaded and an additive, it is almost non existent when i use LRP. I use the car 7 days a week and cannot always find a garage that sells LRP. Is this going to do untold damage to my engine if i use unleaded? Do i have to alter the timing to run on unleaded.
The motor runs like a dream until i switch off and then i get this embarassing problem.:banghead: Any Help greatly appreciated

[B18 GPC]

Unleaded with additive should be good enough .

i advanced my timing a few weeks back , on the dizzi , which gave me great running and performance and a few "chugs" of over run..

since i serviced the car the engine is pinking and runs naff but no over run , so need to set up the Co again and the timing - id imagne if its freshly serviced , with plugs , air and fuel filters { if fitted } are changed , run it to your local test station for an emmisions check , set it up about 2.5Co and Get them to set up the timing for you too....

£30 half hours labour , got to be worth a go? ..

In answer to your question , i'd look at timing ..

[E_T_V]

The timing is done electronically on the S series.

The 88 model won't be unleaded compatible though so you may suffer from valve seat recession after a while. I'd use diet unleaded plus an additive, or optimax + additive if you are feeling flush as LRP is pretty much non existant round here now. If you get valve seat recession then you can fit hardened valve seats when it happens or an unleaded compatible head.

The usual cause of running on (i.e. when you switch the engine off but it doesn't stop), is something wrong with the fuel sytem. It may be as simple as the idle speed it too high. However other common problems are split vacuum hoses, faulty carb diaphram valves and sticking ORFCO valves are all fairly common too.
If you have a search you'll find advice on how to check all of these and eliminate them as a possible cause.

[G Force]

I The problem i have is that the engine runs very very hot yet the guage only ever reads a quarter unless i am stationary then it reads half. when i turn the engine off it continues to run for a couple of seconds and makes a terrible fracas under the bonnet.
Any Help greatly appreciated


Hi Andy, it sounds like the reason for the running on when switched off is that the idle speed is too high due to the engine not getting up to full temp caused by a sticking thermostat. This causes the autochoke to stay on a little.

First thing to do is to fit a new 88 degree thermostat, this should slow the idle speed down.

If fitting the new thermostat does not cure the running on altogether then you will need to reset the idle and fast idle carburettor settings. Details howto do this can be found under the FAQ section on tuning the S series.

You should continue to use unleaded petrol + additive, and in the meantime while you fix the thermostat try switching off the engine in Drive, this should help reduce the running on.

Cheers Gary :)

[henocsr]

if using unleaded i would recomand that you use super unleaded and an additive, as the ron rating will affect the engine running as the ecu is programmed for 97 ron fuel.

[E_T_V]

The engine has a knock sensor built in which should take care of the timing adjustment. Super unleaded won't hurt of course but normal diet unleaded + lead replacement additive should work too.

[BenGMain]

if using unleaded i would recomand that you use super unleaded and an additive, as the ron rating will affect the engine running as the ecu is programmed for 97 ron fuel.

I'm not sure how much relevance this has, as I have an R-Series rather than an S-Series in my car, BUT...

I first used 'diet' unleaded and redex, then i found using super unleaded with the redex gave me a better MPG.

But now I use diet unleaded again, but with Castrol Valvemaster Plus, which has a 'built in octane boost'

...and with the difference in price between super and diet, I'm not paying so much fuel duty.

I think my logic is sound :confused:

[e692wtt]

Your logic is sound :thumbup: .

In my 1988 1600 (S-series) I use Morris Superblend Zero Lead (which doesn't have an octane improver) with 95RON 'premium' unleaded - but using 95RON plus Castrol Valvemaster Plus, while being slightly poorer value for money, made a great difference :) and costs a fair bit less than using 98RON fuel with an additive.

When using an unleaded additive, make sure it has the 'FBHVC' (Federation of British Historic Vehicles Clubs) 'mark' as this is a guarantee of valve seat protection that non-marked products cannot guarantee. CAstrol Valvemaster and Valvemaster Plus have FBHVC approval, as does the Morris Superblend stuff and also a couple of other products.

[andybharris]

When i said previous about the temp gauge only reading below a quarter the engine feels terribly hot and the bonnet extremely hot to touch. Surely if the thermostat was stuck open then this would make the engine colder. is there anyway of checking the temp guage is accurate at a specific temperature:o

[G Force]

When I said previous about the temp gauge only reading below a quarter the engine feels terribly hot and the bonnet extremely hot to touch.

Hi, I hear what you are saying;) , but with your other symptoms, and if there are no other physical signs of overheating, (coolant leaking from expansion tank cap, cooling fan on etc.) I would be inclined to believe the gauge and put the heat down to the extra heat generated by the auto transmission. If you feel that the engine is overheating, I would first check that the cooling fan works by shorting the two wires together on the rad fan switch located on the side of the radiator. If the fan is working run the engine stationary on a fast idle to see if the fan comes on when the gauge reads around 3/4. This is normal and you can more or less rule out the engine overheating.

Surely if the thermostat was stuck open then this would make the engine colder.

Yes this is what I was alluding to, as the symptom you describe when the gauge reads a quarter when driving and then reaches half way when stationary is a very common description of what happens when the thermostat sticks open. This condition is also often accompanied by a higher than normal idle speed due to the auto choke staying on a little, which also can result in the engine running on when switched off.

is there anyway of checking the temp gauge is accurate at a specific temperature:o

You can check the fuel ecu's response to the coolant temp sensor defaults, if you pull the coolant sensor plug off of the sensor in the thermostat housing the temp gauge should read a quarter. If you short the wires in the plug together then the gauge should read over 3/4 and the high temp warning light should flash.


Cheers Gary:)

[andybharris]

The Auto choke has been diabled/removed, it runs on a manual cable choke. if i stop the car in Drive it is perfect. probably Because the idle speed is lower and the engine will be laboured because of trying to propell the car forward i presume, i shall change the thermostat this weekend, i also have a sump gasket to renew and i may apply some new underseal Cheers Andy

[G Force]

The Auto choke has been diabled/removed, it runs on a manual cable choke. if i stop the car in Drive it is perfect. probably Because the idle speed is lower and the engine will be laboured because of trying to propell the car forward i presume,


Andy, because the autochoke has been disabled then changing the thermostat won't help the running on I'm afraid. If the thermostat is sticking open then it could even run on more in theory.

However if the thermostat is sticking open then the temperature gauge will read correctly once you fit a new thermostat.

Many cars get converted to manual choke because of problems with the temperature gauge or running problems, that are either too expensive or too hard for the garage to solve. I expect that this is what has happened in your case.

The ECU that controls the autochoke also drives the temperature gauge, so the gauge still relies on recieving accurate engine temperature information from the sender unit and that the fuel ECU interprets that information correctly, even though the choke has been converted to manual choke. Your temperature gauge problem may be caused by either the engine running cool or the gauge recieving wrong information.

It is possible to convert the gauge to work from a standard type of sensor and bypass the fuel ECU if you do a search there is detailed info on how to do this, if the thermostat is not the cause of the problem. One thing I don't like about this conversion is that it does not allow the programmed ignition ecu to recieve correct engine temperature info anymore.

The fact that the autochoke has been disabled, I suspect the reason you are experiencing running on is due to the idle speed set too high or an excess of carbon build up in the combustion chamber. If slowing the idle speed does not help then I would just keep switching off in D untill such times you decide to convert the cylinder head to run unleaded.

Hope this is helpful but any questions just ask.

Cheers Gary :)

[BikerGran]

I run my 1.6 auto on ordinary unleaded with Castrol Valvemaster. Tried it with the super unleaded but it didn't seem to make a difference. The odd thing is that it actually seems to prefer the ordinary Valvemaster without the octane booster.

I've had running on problems but usually associated with faults in the vacuum system - leaks or pipes come off. It does it a bit anyway but I always let it idle in 'drive' for a few moments then switch off in drive, seems to do the trick.

[Jullian_browne]

hello
mine to runs cool when driving and then get up past middle when standing
trying to suss out why?

[E_T_V]

Faulty thermostat. Its stuck open and so overcooling the engine when on the move, but gets up to normal temperature when stationary.

[BikerGran]

Just to confirm I had exactly the same problems with temp gauge which were solved by replacing the thermostat.