Thanks in advance for any assistance with the problem I'm about to describe.
Been through quite a few possibilities already so will give as much background as possible.
This will be a long opening post and I apologise for that but it'll hopefully save time in the long run as I wont have to waste people's time replying with "Already done that" etc.
Assume a certain level of car 'know how' but not specific Renault knowledge.
Car is my wife's 2004 Megane II 2.0 petrol 6 speed CC.
Started causing problems when getting a little warm and would stutter before cutting out. Would restart immediately and without problems, even whilst still coasting after cutting out. 10 minutes later same thing would happen. Eventually stopped running completely once warm (except on tick over) and even whilst cold there is a pause before revs pick up if throttle is pressed too quickly. Slow throttle application sees the revs rise without a problem. The very moment the car is started for the first time on any given day it will run perfectly for the first five or so seconds. Then the pause before revs climb will gradually get worse.
Passed it to the garage I usually use for remedial work and they instantly said Catalytic converter blocking up/breaking down. Others said the same. I was reluctant to go down that route so (with some help from this forum as a visitor) I cleaned up the Crank Position Sensor (front of bellhouse looking at radiator). I tried a new MAP sensor. Cleaned up the throttle body/MAF and all other sensors I could get to. No difference. Checked all the air intake tract for issues and nothing. Tried running it with airbox disconnected (air straight into throttle body) - no difference.
At this point everyone I had previously asked was, of course, telling me to just get on and cut the bottom off the cat, clear it out, then once proven it was a cat problem fit a new one.
Against my better judgement I did that. Car now has a completely gutted cat and... no improvement.
Changed the in tank pump. No difference.
Tried running with the fuel filler flap wedged open a little. No difference.
Cleaned all the plugs (very black from engine running too rich). No difference.
Checked all plug leads for signs of shorting. Nothing. All coil packs look to be clean and the plugs were evenly black as opposed to one or two which would have given me a clue.
Now. As far as I can see there is no fuel return to tank on this car? It has a closed loop system? Could there be something faulty within this which is causing the system to pressure up and force too much fuel through the injectors?
Is there a cold start device / enrichmnent control somewhere and perhaps the engine is stuck in cold start mode?
Best way I can describe the massive pause before revs climb by the way is an old carb' car with no air filter on and the mixture whacked right up. Stab the throttle and there is a huge gulp of air before the revs catch and climb.
Honestly - this car is killing me. Words cannot describe how grateful I would be for a tip off or clue that leads me to the solution. I'm not against buying new parts for it but don't intend to keep buying things based on possibilities. I prefer to clean parts up first to try and locate the issue and if there is an improvement then I will renew without hesitation.
Sorry for the massive post.
Been through quite a few possibilities already so will give as much background as possible.
This will be a long opening post and I apologise for that but it'll hopefully save time in the long run as I wont have to waste people's time replying with "Already done that" etc.
Assume a certain level of car 'know how' but not specific Renault knowledge.
Car is my wife's 2004 Megane II 2.0 petrol 6 speed CC.
Started causing problems when getting a little warm and would stutter before cutting out. Would restart immediately and without problems, even whilst still coasting after cutting out. 10 minutes later same thing would happen. Eventually stopped running completely once warm (except on tick over) and even whilst cold there is a pause before revs pick up if throttle is pressed too quickly. Slow throttle application sees the revs rise without a problem. The very moment the car is started for the first time on any given day it will run perfectly for the first five or so seconds. Then the pause before revs climb will gradually get worse.
Passed it to the garage I usually use for remedial work and they instantly said Catalytic converter blocking up/breaking down. Others said the same. I was reluctant to go down that route so (with some help from this forum as a visitor) I cleaned up the Crank Position Sensor (front of bellhouse looking at radiator). I tried a new MAP sensor. Cleaned up the throttle body/MAF and all other sensors I could get to. No difference. Checked all the air intake tract for issues and nothing. Tried running it with airbox disconnected (air straight into throttle body) - no difference.
At this point everyone I had previously asked was, of course, telling me to just get on and cut the bottom off the cat, clear it out, then once proven it was a cat problem fit a new one.
Against my better judgement I did that. Car now has a completely gutted cat and... no improvement.
Changed the in tank pump. No difference.
Tried running with the fuel filler flap wedged open a little. No difference.
Cleaned all the plugs (very black from engine running too rich). No difference.
Checked all plug leads for signs of shorting. Nothing. All coil packs look to be clean and the plugs were evenly black as opposed to one or two which would have given me a clue.
Now. As far as I can see there is no fuel return to tank on this car? It has a closed loop system? Could there be something faulty within this which is causing the system to pressure up and force too much fuel through the injectors?
Is there a cold start device / enrichmnent control somewhere and perhaps the engine is stuck in cold start mode?
Best way I can describe the massive pause before revs climb by the way is an old carb' car with no air filter on and the mixture whacked right up. Stab the throttle and there is a huge gulp of air before the revs catch and climb.
Honestly - this car is killing me. Words cannot describe how grateful I would be for a tip off or clue that leads me to the solution. I'm not against buying new parts for it but don't intend to keep buying things based on possibilities. I prefer to clean parts up first to try and locate the issue and if there is an improvement then I will renew without hesitation.
Sorry for the massive post.
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