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Discussion Starter #1
Hi Folks.

Hope I have more luck with suggestions on this query than on previous ones for my Clio, none of which has inspired anyone to put fingers to keyboard! Strange - there's usually so much help here.

Since we bought this Scenic July 2010 it's been a poor starter. It's been looked at several times and the following things have been done:

All pencil coils replaced
TDC sensor replaced
New air filter
New spark plugs
New cambelt, water pump (not related to starting problem, just needed doing)

It takes numerous turns of the starter to fire and then is 'lumpy' until the accelerator is blipped. This is usually accompanied by a strong smell of petrol. Once this is out of the way, however, it runs pretty smoothly and sounds fine.

Compression has been tested - within tolerance on three cylinders, about 15% down on the remaining one.

No coolant in oil or blowing into coolant.

It's just a feeling, but I have got the impression that it starts better on a cold, frosty morning than a warm one.

If I re-start within a minute or two of stopping it usually fires within a couple of revs, whether the engine is warmed up or not.

Could the air inlet temperature sensor be faulty?

Could an injector be faulty?

Can't afford endless trips to the garage for hit-or-miss diagnostic work and anyway the car's been on analysers several times in the last few months and no obvious faults have been found - no fault codes.

Any ideas anyone - all suggestions (clean ones) gratefully received!

Thanks.

Oh - and if you could take a look at my Clio queries I'd appreciate it - just search for threads under my handle. Cheers.
 

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Pull the spark plugs and check their colour and if they are of equal colour.

The smell of petrol sounds like the engine is overfueling for some reason or unburnt fuel is entering the exhaust.:)
 

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Discussion Starter #3 (Edited)
Well, that's been done before - when I decided to change them. One plug is slightly oily and darker than the others. My guess is that it's from the cylinder with the reduced compression, as I've posted before.

Ditto the smell of petrol - but how can you tell if the engine is overfuelled? I would say that the smell of petrol comes from the engine turning over 5-10 times without firing, so unburnt fuel is being squirted into it and thence the exhaust and that's what smells. Don't get any backfiring, though.

All in all it's a mystery and a tedious one. I suspected the air temperature sensor because if the ECU thought the ambient air was warmer or colder than actual, it might be allowing too much/too little fuel through the injectors at start-up. As I said, it certainly starts better on a cold and frosty morning.
 

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The engine coolant temp sensor has a greater influence on the fuel mix during starting - has it been checked.

It may also be worth double checking the wirng connections to the TDC sensor.

Have you any idea of what figures were recorded in the compression test?:)
 

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Discussion Starter #5
No, the coolant temp sensor hasn't been checked - interesting thought, though - do you have any figures for resistance etc?

I don't have the compression test figures unfortunately, but they were carried out by a garage recommended by the local member of the Federation of Engine Re-manufacturers, so I am reasonably confident they were kosher.

In addition, I have treated the system with SteelSeal in case there *was* a head gasket leak and also cleaned the engine's combustion train with EcoTek Powerboost, which seems to be well-recommended by some people who ought to know, in case injectors and/or valves/valve seats were dirty/gummed up. I think the engine runs more freely but the starting problem remains.

Do you have, or know where I can find, resistances for the pencil coils, so I can test them as well?

Thanks a lot.
 

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Excuse my ignorance my experience is limited to diesel engines but could it be air entering the line somewhere? This could explain the smell of pertrol and the lumpy initial running as everything else seems to be fine. Certainly diesels perform have these symtoms with a small air leak.
 

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Discussion Starter #7
Re: 02 Scenic 1.6 Auto - *still* reluctant to start!

Can't comment on the possibility of air in the line as I don't know enough about the subject - maybe someone else does?

In the meantime, the saga continues.

Today I tried replacing all the pencil coils with the new green top Valeo "4th generation" units that are supposed to be better made and more reliable. Two were brown tops and two were grey. I also changed the spark plugs *again*, this time to NGKs to OE spec.

On taking out the Bosch Super 4s which have only been in place a few months, I found that they all had oily threads but clean brown tips, while one plug was actually dripping oil! The tip was the healthy brown of good ignition but the whole plug was wet - I am sure it was oil, not petrol - I had to grab a rag to wipe the oil off. It was the No.1 cylinder, at the flywheel end.

So, forking out 70 quid on new coils and plugs made absolutely zero difference, apart from eliminating them as the possible cause, which is partly why I did it. The engine, which was semi-warm, still takes numerous turns to start firing and then does so, but very lumpily for a few seconds, as usual, then it evens out and runs smoothly. Still get occasional hesitation/misfiring under acceleration, however.

Just to re-cap: TDC and ECT sensors have been replaced recently, as both have been suggested as possible culprits, to no avail. Soon I will have an engine composed of replacement parts, at enormous cost!

I'm planning to take out the fuel injectors next and see what state they're in.

There's something weird going on in my engine and I suspect it's not good. Car's just reached 80k miles. I would get rid of it but being a bankrupt no-one will lend me the money to buy something better!

Anyone got any ideas? Leaky valves?

Getting desperate now!
 
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Re: 02 Scenic 1.6 Auto - *still* reluctant to start!

Could be worth doing a compression test i suppose.
Has the fuel filter been changed?
 

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Discussion Starter #9
Compression was done - see earlier in the thread. Three cylinders found to be within tolerance and one about 15% down.

Haven't checked fuel filter - yet! Just had a look at the Haynes manual - looks like a fun job (not). Can I do it with ramps or does it need a pit/lift, d'you reckon?
 

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You say one cylinder was 15% down on the compression test. That tells you nothing without the actual figures. Plus a dry followed by a wet compression test would be more informative.

The £70 spent on coils, etc may have been better spent on a proper diagnosis.

There should be no oil down the spark plugs so I suggest you get that aspect investigated.:)
 

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Discussion Starter #11
Noted - but I felt these two areas needed to be eliminated properly because the lumpiness/misfiring is symptomatic of ignition trouble.

I presume that investigating oiliness on the plugs will mean taking the head off or at least the valves and I just don't have the money for that and don't feel confident of doing it myself, so it will have to remain a mystery for the time being.

I had an east end friend who could arrange for an unwanted car to be 'stolen', taken 'down the docks' and torched. I think this car qualifies for that special treatment!
 

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Noted - but I felt these two areas needed to be eliminated properly because the lumpiness/misfiring is symptomatic of ignition trouble.

I presume that investigating oiliness on the plugs will mean taking the head off or at least the valves and I just don't have the money for that and don't feel confident of doing it myself, so it will have to remain a mystery for the time being.

I had an east end friend who could arrange for an unwanted car to be 'stolen', taken 'down the docks' and torched. I think this car qualifies for that special treatment!

The oil leak could be something as simple a leaky cam cover gasket.

Paying someone to do a decent diagnosis may have you saved you money rather than embarking on a replacement parts spending spree.:)
 

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Discussion Starter #13
It hasn't been quite that simple, I'm afraid. When we booked the car in to have its cam belt and water pump changed we asked the garage (which had good local recommendations) to investigate the starting problem.

They replaced two pencil coils and, after I told them about a recommendation from this forum that the TDC sensor could be to blame, replaced it. None of that made any real difference and that garage didn't suggest any other avenues to explore.

That added £300 to a £360 bill.

Next came the compression test - £40

I replaced the spark plugs - £18

Most recently our local mechanic, who only charges £15 per hour but comes highly recommended (wish we'd known about him before cambelt change episode) changed the other two coils as he said one was open circuit and that as they operate in pairs it was best to change them both. - £50

So quite a lot of money has been spent on abortive diagnostic work already and I only decided to change the coils again because they were two different pairs - brown and grey tops - and because these pattern parts have such a poor reputation for reliability. As the spark plugs were cheap and numerous people had posted here that it was best to stick to OE plugs, I felt it was worth changing them at the same time.

Here's the thing: if you're not an expert mechanic yourself (and I'm not), how do you know who is going to do a proper diagnostic investigation or indeed what constitutes such an investigation?

How can anyone tell if the cam cover gasket is leaking if it's not coming down the outside of the engine?
 

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Discussion Starter #15
Hi Dan.

I'm at the A*s*-end of the universe :d: lovely north Norfolk!

The car is indeed driveable and I use it most days - have no choice - but I worry about continually squirting doses of unburnt fuel into the cat and of course the starting problem is an additional strain/load on the starter motor and battery.
 

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Discussion Starter #18
Well, just had the fuel injectors out and they look clean and identical. Checked their resistances and they were all spot on, so whatever the problem is, it doesn't appear to be fuelling.
 

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Discussion Starter #19
Been in to another garage today but nothing untoward found in diagnostics. Garage suggested a leak test be done on the engine and sent me down the road to a specialist, but although they do engine rebuilds, they don't do leak testing.

Discussed the matter with them and they felt it was unlikely to be a mechanical problem - more likely over-fuelling and/or some weird electrical problem that could be impossible to trace.

So, unless anyone with a Scenic of the same vintage and engine has come across this problem before, I think I've come to the end of the line.

It was suggested that the best answer to my problem was to get rid of the car!
 

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Discussion Starter #20
Well, have given up on trying to solve this - no-one seems to be able to get to the bottom of it - so am trading the wretched car in for an 08 Kia Cee'd with 20k on the clock and four years of its warranty remaining.

I do like my Scenic and will miss its comfortable ride and versatility but Renault reliability issues are just too much to live with.

Oh, and at the weekend our Clio let us down *again* and had to be transported home after refusing to re-start following refuelling. Breakdown guy thought it might be the TDC sensor. It was p*ss*ng with rain and we had gone 13 miles into a 180 mile journey. So back home to get the Scenic which, although it hates starting, runs fine once it's going and managed the 500-mile weekend without any other problems.

Ok, it's only got 50k on the clock and it is 12 years old, but my 18-year old Suzuki Vitara never, ever, fails to start and never misses a beat. And the Clio's aircon has stopped working (not pressure) but can't face (or afford at the moment) the cost of having it fixed.
 
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