Renault Clio, 1994 M, 1.4RT, 56,000 miles, main dealer maintained. Owned from new.
1) Every morning when I go to work, within half a mile of starting, the engine will always stutter once. Doesn't happen again, is fine for the rest of the journey. Same happens in the evening on the way home. It's been like it for about a year and a half. You can almost predict where on the road it will happen. I replaced the distributor and rotor arm at Xmas, so can't be them. Could it be the HT leads? They are still the originals, i.e. nearly 10 yrs old. If so, why does it only do it once per journey. Car mostly used for short journeys - could it be that?
2) When you pull up at a junction, the engine is always slow to return to idle - first drops to 1500rpm, then slowly to idle (around 850rpm) rather than drop directly to 850rpm. Any clues as to why?
Drives fine apart from these 2 annoyances!
Thanks for your input!
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Sounds to me like the ECU reducing the enrichment as the engine warms up, but doing it too suddenly or by a large amount. Can usually just detect it on an engine running correctly.
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I would suspect the connection to the temp sensor or the sensor itself which may explain why the tick over picks up. This could still be a plug lead problem although the fault is so short lived I doubt it but still recommend you check the resistance of all HT leads. They should be about 2.5 K ohm per foot if one is faulty due to heat and corrosion at the plug end it will have risen to way over 10K ohms.
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The slow return to idle is normal. The stutter could be the change from open to closed loop of fuelling system, ie the point at which the management system goes from a programmed fuelling mode on warm up to where the sytem becomes controlled by the various sensors including the oxygen sensor. A dose of Forte Gas Treatment and a few longer runs may clear it by making the oxygen sensor switch more quickly and accurately. A professional diagnosis may be needed.
Andrew
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Finally managed to buy some Forte Gas Treatment, kind of hard when you are a member of the public!
Added a bottle of it to a full tank and have used about half the tank of fuel including a 60 mile dual carriageway journey when I kept it in 4th at about 4800rpm.
Problem of stuttering once per cold start journey is still there though at the moment.
1) Does it just take a little longer for the Forte Gas Treatment to work or is it worth me trying it at a higher concentration, i.e. a whole bottle to half a tank of fuel?
2) How easy is it to replace the oxygen sensor - does one end just go into the downpipe and the other plug in somewhere?
Just trying to eliminate the obvious or fix it myself before donating large funds to a garage.
Btw, rotar arm, distributor cap and HT leads are all about 6mnths old.
Thanks.
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Now the weather's warmer than when you first posted, does the point at which the stutter occur come earlier (indicating it's related to how fast the engine warms up)?
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Spot on Vista1100.
Now it is warmer than when I first posted, the point at which the stutter occurs definitely does come earlier in the journey.
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Well, I would suspect that it may be when the engine switches from open-loop to closed loop, and its happening before the oxygen sensor is hot enough to switch rapidly enough to keep engine running smoothly (i.e. without large mixture fluctuations). Two possibilities:
1. EGO sensor is bad (perhaps heater is not working properly) - most likely. Or maybe problem in heater feed circuit?
2.Temp. sensor is over-reporting engine temp so ECU is swithcing to closed loop a bit prematurely.
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Sorry to sound stupid, but what is the EGO sensor? Is it the same as the oxygen sensor?
Is there anything I can do?
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Sorry, EGO = Exhaust Gas Oxygen
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Spoken to Forte technical support and they recommend using the Gas Tratment in a higher concentration for a very high direct hit, trying 1 bottle of gas treatment to 1/4 to 1/2 tank of fuel, allowing this to run through and then add fresh fuel to the tank and assess the vehicle.
As I've got a bottle left I'll try this first, if not investigate the EGO sensor as suggested. Anyone know roughly how much a replacement for a 1.4rt Clio is?
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New sensor shouldnt be more than £50-60, buy a Bosch from a Bosch agent if Renault want shedloads more. Coolant temp sensors notoriously unreliable so may be worth investing around £15 and a few minutes to fit.
Usually apply the Gas treatment as a concentrate ie one bottle to a nearly empty tank followed by another bottle to a tankful.
Andrew
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