Help me out please... Stupid family Renault broken again...
Discussion
Funny how as soon as you get a bit of money saved, the b
d car goes and breaks itself...
We've got an 04 Renault Megane Scenic 1.6 vvc as our family car. Today my partner calls to tell me its running really rough and wont rev properly. Feels like its going to stall all the time. I'mat work at this time so just tell her to limp home an I'll look later.
I get home from work and have just been out trying to diagnose the fault.
It starts fine, on the button, but idles rough. The engine shakes like a bastid BUT, if you rev it whilst at stand still, it judders a little at the touch of the pedal but then revs perfectly normally. Certainly doesn't rev like its firing on 3 cylinders for example, yet it idles like it is.
Take it out around the block and it drives but is very low on power and loud, just like it's only firing on 3 cylinders.
So I get back, assuming a coil must be dead so pop the bonnet and one by one, unplug them to highlight which one is dead... None of them appear to be. Disconnecting each of the plugs either stalled the engine or killed the idle almost to the point of dying. The only other oddity I did notice was the sulphur smell from under the bonnet, pointing towards a Cat fault, but would a dead cat cause the above running symptoms?
Why would the car idle as if on 3 cylinders but when reved be fine, but reved under load act as if on 3 cylinders? Could a blocked exhaust cause this?
At the moment, my next plan is to give it to a garage to read the fault codes as the dash has lit up like a christmas tree. At least it will point me towards the fault. Any advice appreciated.
d car goes and breaks itself...We've got an 04 Renault Megane Scenic 1.6 vvc as our family car. Today my partner calls to tell me its running really rough and wont rev properly. Feels like its going to stall all the time. I'mat work at this time so just tell her to limp home an I'll look later.
I get home from work and have just been out trying to diagnose the fault.
It starts fine, on the button, but idles rough. The engine shakes like a bastid BUT, if you rev it whilst at stand still, it judders a little at the touch of the pedal but then revs perfectly normally. Certainly doesn't rev like its firing on 3 cylinders for example, yet it idles like it is.
Take it out around the block and it drives but is very low on power and loud, just like it's only firing on 3 cylinders.
So I get back, assuming a coil must be dead so pop the bonnet and one by one, unplug them to highlight which one is dead... None of them appear to be. Disconnecting each of the plugs either stalled the engine or killed the idle almost to the point of dying. The only other oddity I did notice was the sulphur smell from under the bonnet, pointing towards a Cat fault, but would a dead cat cause the above running symptoms?
Why would the car idle as if on 3 cylinders but when reved be fine, but reved under load act as if on 3 cylinders? Could a blocked exhaust cause this?
At the moment, my next plan is to give it to a garage to read the fault codes as the dash has lit up like a christmas tree. At least it will point me towards the fault. Any advice appreciated.
so if he cat had failed and was blocking the exhaust, could the car potentially drive so down on power that it acts as if it's running on 3 cylinders?
Your thoughts about the low idle make sense. I certainly doesn't rev on he drive like it's missing a cylinder, only when you put it under load.
Your thoughts about the low idle make sense. I certainly doesn't rev on he drive like it's missing a cylinder, only when you put it under load.
Yup to be honest from what my partner described on the phone I was a bit worried it may be the dephaser and knocked the timing out but having driven it, i'm not so sure.
It idles rough but as under powered as it is, it still drives smoothly. If the timing was out it would be misfiring and kangarooing all the time. Plus as said, on the drive it revs fine. I've driven cars with timing out even just a tooth on the crank out and it was nothing like driving this.
It idles rough but as under powered as it is, it still drives smoothly. If the timing was out it would be misfiring and kangarooing all the time. Plus as said, on the drive it revs fine. I've driven cars with timing out even just a tooth on the crank out and it was nothing like driving this.
Out of curiosity, assuming the car has one, if I were to remove the pre cat lambda sensor, making a large hole in the exhaust before a potential blockage, should the idle pick up now the gasses have a clear exit to escape?
Just thinking of simple ways to diagnose this rather than paying £££ at a garage for them to plug it in...
Just thinking of simple ways to diagnose this rather than paying £££ at a garage for them to plug it in...
MysteryLemon said:
Out of curiosity, assuming the car has one, if I were to remove the pre cat lambda sensor, making a large hole in the exhaust before a potential blockage, should the idle pick up now the gasses have a clear exit to escape?
Just thinking of simple ways to diagnose this rather than paying £££ at a garage for them to plug it in...
If you are not in a particular rush buy an OBD2 tester off Ebay and plug it in yourself. Or try to buy one locally.Just thinking of simple ways to diagnose this rather than paying £££ at a garage for them to plug it in...
I've only fixed one car with a collapsed cat and it was a very strange set of symptoms. It was so long ago I can't remember how we came up with the idea it was the cat. But as you say, started on the button, rough idle and a wierd low power feeling without a definite missing cylinder.
We pulled thhe cat off and smashed the insides out and it was fine after apart from a not very nice howling from the hollow cat chamber.
We pulled thhe cat off and smashed the insides out and it was fine after apart from a not very nice howling from the hollow cat chamber.
Old school: Pull the plugs and see if any are damp with unburned fuel or black.
A cheap Bluetooth OBD reader is very handy for DIY car diagnostics (assuming electrical/sensor related issue) - get yourself one. They're less than a fiver on eBay http://www.ebay.co.uk/itm/V2-1-ELM327-OBDII-OBD-2-...
A cheap Bluetooth OBD reader is very handy for DIY car diagnostics (assuming electrical/sensor related issue) - get yourself one. They're less than a fiver on eBay http://www.ebay.co.uk/itm/V2-1-ELM327-OBDII-OBD-2-...
MysteryLemon said:
996TT02 said:
Methinks you are going to end up in the penny wise, pound foolish trap.
A blocked exhaust doesn't require a car to be plugged in to tell me so. A few bolts and I'll know whether it's blocked or not.A banana in the exhaust won't do that.
Your call, but you are on here asking for advice, perhaps you should try what you are suggesting first then if you are determined to do so? Then take it from there? Seems a lot easier to just plug something in FIRST. But that's just me, I'm weird like that, doing things logically.
996TT02 said:
"...my next plan is to give it to a garage to read the fault codes as the dash has lit up like a christmas tree."
A banana in the exhaust won't do that.
Your call, but you are on here asking for advice, perhaps you should try what you are suggesting first then if you are determined to do so? Then take it from there? Seems a lot easier to just plug something in FIRST. But that's just me, I'm weird like that, doing things logically.
But a failed cat would cause lambda reading faults which would light the dash up (it's flashing "check emissions").A banana in the exhaust won't do that.
Your call, but you are on here asking for advice, perhaps you should try what you are suggesting first then if you are determined to do so? Then take it from there? Seems a lot easier to just plug something in FIRST. But that's just me, I'm weird like that, doing things logically.
I also don't have the ability to just plug it in first and see. I would rahter diagnose and fix the fault without paying a penny to a garage. I've diagnosed problems on and repaired faults both mechanical and electrical on ever car I've ever owned without the need of a computer to tell me where to look.
Pretty sure I can rule out the coils/sparks as unplugging them one at a time would highlight a faulty one of either.
the failed cat/blocked exhaust idea makes sense in my head to a point and again can be diagnosed with a few bolts I'll try tomorrow. Plus the car stinks of sulphur after running for a min or two. This wouldn't happen unless the cat was at fault surely?
Dephaser pulley worrys me but as said, the symptoms aren't as you would expect. If it was failing and taking the timing with it (as it would) then the car would be misfiring and drive lumpy. It doesn't, its smooth but underpowered.
Edited by MysteryLemon on Thursday 15th January 22:03
Edited by MysteryLemon on Thursday 15th January 22:17
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