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Running problems on 98 octane

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DaveP

Enthusiast
Messages
147
Hi all,

looked through old threads to see if my question had been answered already, can't find anything though.

I've recently got myself a 1984 R4L which was running well on 95 octane fuel but since I put a tank of 98 octane in the other day it's started to die at low speeds, through town etc, seems to be ok at high revs though, have I bought dodgy fuel or do I simply need to adjust the timing? I've done 10 trips over 50km at reasonably high speed with no probs at all and this problem arose almost straight away when I filled up. Thinking I'll drain the tank, refill with 95 and give her a thrash around for half an hour.

Any advice would be much appreciated

Dave
 
Hi and welcome.

I switch from 95 to 98 in France and have never noticed a difference. There should be no need to adjust anything.

It does sound like a problem with the fuel. There's an outside chance of fuel vaporisation if you were on the limit before. Is your radiator cooling fan working? Mine dies in town on hot days when that's broken, but is fine on a run.
 
Hi Malcolm,

It's not overheating, actually gets a little hot uphill at 120kmh, but that's only fair really. It was a cold day by local standards when this happened and it started happening striaght away the next morning, idle has got lumpy too and then she needs coaxing to rev enough to pull away.

Looks like I'm the latest one to learn the cheap supermarket fuel lesson.

I'll do the drain/refill on Friday and post an update, might advance the ignition a tiny bit too.

Thanks
 
Malcolm, why do you switch from 95 to 98 in France?

We usually get cheap supermarket 95 petrol and the cars run OK. BTW not that cheap as it's 1.26 euros here. :(

DaveP, you must be peddling very hard to do 120 going uphill!
 
Rabbits and Red Herrings.

Hi All - Got to agree with our leader, I ran on 95 and 98 octane and it never made any difference - if it's not overheating then it's likely a fuel starvation/blockage or ignition issue. Sometimes running probs coincide with certain actions/habit changes yet are unrelated - very confusing and often creates megga grief - rabbit chasing/red herrings etc.
Gunge sucked up from the tank into the fuel system is a possible especially on our older cars. (Installing an after market in line fuel filter in the fuel line before the fuel inlet on the carb is a wise idea if you have'nt already got one.) In the past, water contamination in fuel at some 'older' garages caused havoc in the past - severe running probs :eek:, but in these 'modern' days it's much rarer/unlikely.
If the engine is 'hunting'/gutless at tickover+ check points/ sparkplug gap. Dodgy/failing coil when it warms up plays havoc - swop with a spare -cheap to buy and easily available/worth renewing anyway. Finally the carb - from memory there's a gauze filter on the inlet which could be restricting fuel - my memory is failing. It's much quicker/easier to eliminate ignition before you finally end up stripping down the carb.
Keep it simple or you'll end up with a lot of grief/unnecessary stripping /rebuilding - the 4 is very robust and legendary for it's ability to happily 'soldier on'/ keep going. ;)
Ouch Bleubelle :shock: - lpg conversion could be 'on the cards' for 'La Belle Blanche'. :smile:
 
Bluebell said:
Malcolm, why do you switch from 95 to 98 in France?
Click to expand...

I see 98 octane as a special treat for the poor neglected thing. Wouldn't try it over here as the price difference is much more than it is in France. Doesn't actually make any difference unless the car has pinking problems on 95 octane.
 
Yes, the 98 is only 3c more expensive.

Brian, I'd rather be paying 1.26 in deepest France than £1 in Leeds!

Malcolm, I know you were intending to dash over here to put a new head gasket on Blanche. No need now as she got so bad I took her to the local garage where they not only did the job but left her innards immaculately shiny and clean. Also sparkly new spark plugs, water pump, thermostat etc. She's like a different car.

But we will be pleased to see you if you can make it over here later in the Summer. At the moment it's 28 degs and wall to wall sunshine. :cool:
 
Hi Bluebell, missed you. Glad Blanche is all better now.
 
Well, Wing Commander, it's a long story. The roofer cut the telephone wire and France Telecom said they'd come and mend it but didn't say which month and then, because we had moved house, t'internet took another two weeks to transfer. Honest, m'lud.
 
Red Herring seems to be exactly the case Le Champ

Cracked the carb open, just to check before I siphoned 25 litres of fuel out, float chamber full of rust, cleaned it out and I'm back on the road. I suppose filling the tank to the brim must have shifted all the rubbish from the bottom. Always the most obvious thing isn't it? Off to pick up a fuel filter this afternoon. Would it be best before the fuel pump or between pump and carb? Bit low on coolant too which would explain the overheating, think I'll go the whole hog and chang oil and filters since I'm off work today.

I couldn't be more pleased with the little 4, I was going to buy an ami 8. Certainly wouldn't have had any problems at 120 kmh in one of those
 
I'm glad you've managed to get it all sorted, I think everyone was wondering what had gone wrong with your 4
 
Hmm, sorted and then very rapidly unsorted, similar issues carried on for a bit when I serviced the car and fitted the fuel filter. Then the car overheated very quickly. I checked all the inlet side gaskets and found no probs, then I noticed a bit of air in the fuel filter, tried allsorts to get rid of it (ending up with a mouthful of fuel at one point!) and eventually just fiddled with the idle adjustment a bit and gave the car a run, seems a lot better and the filter is air free, still fluffs a little at tickover, but what carb'ed car doesn't? It's 38 degrees again tomorrow, and I've got 50 kms to go to work so I should find out if the overheating is cured. Constant detective job these old cars.
 
DaveP said:
Hi all,

looked through old threads to see if my question had been answered already, can't find anything though.

I've recently got myself a 1984 R4L which was running well on 95 octane fuel but since I put a tank of 98 octane in the other day it's started to die at low speeds, through town etc, seems to be ok at high revs though, have I bought dodgy fuel or do I simply need to adjust the timing? I've done 10 trips over 50km at reasonably high speed with no probs at all and this problem arose almost straight away when I filled up. Thinking I'll drain the tank, refill with 95 and give her a thrash around for half an hour.

Any advice would be much appreciated

Dave
Click to expand...

I've noticed some rough running when using Shell fuels, no problems with others. I suppose it could have something to do with optimization for the new engine management systems. 98 octane should give a little more bang for your euro but I have no idea whether it's a noticeable difference.
 
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