Renault Megane 1.6 - power loss. - davemar
I've recently had an HT coil replaced on my Megane (1.6 RTe - '98 8v version) after it packed up, along with a new cat after that got destroyed too. Since then the car was running perfectly for a couple of hundred miles, but now its decided to lose some power. It feels like a 1.0l diesel, barely out-accelerating HGVs, and can't get past 4000rpm in 2nd on the flat. It seems to idle OK, so it doesn't feel like a misfire (i.e other HT coil dying).

I've also noticed it's a little noiser than before, possible air leaking type sounds, so I'm suspecting an air leak. But on a quick inspection this morning (on a hot engine - so not much touching things!) the hoses around the inlet seemed OK, nothing obvious.

Any ideas what it could be?

Renault Megane 1.6 - power loss. - M.M

Here is an updated version of a reply I made earlier in the year about a similar problem

Try the cheapest option first.....Remove and examine the rubber vacuum hose from the inlet manifold to the MAP sensor on the bulkhead. Check for splits that may only show up when you bend the hose.

I've had two of these to replace on Megane's. This pipe is quite stiff and short, at certain engine positions the split would open and ruin the MAP input/mixture.

It was happening the most when you were drifting through town at low revs and then tried to pull away, you know how that makes the engine rock on the mounts. Once you had reached a cruising speed the split stayed closed and all was well.

Another symptom was them sounding like they were missing on one cylinder at idle.

They drove so badly at times you could have told the customers they needed hundreds spending but in reality a few minutes and 200mm of small bore hose cured it.

Get a small screwdriver or knife and lever off at the ends, they are only a tight push fit.

On the two I dealt with the hoses looked perfect at rest...the cracks were on the insides of the 90 deg bends and only opened up as the engine rocked in running.

Also has yours had the modified valve cover gasket? They had problems with these leaking oil into the plug wells. It caused oil and muck to build up that could cause misfiring. The Renault updated item is under a tenner and easy to fit.


Renault Megane 1.6 - power loss. - davemar
Thanks for those tips, I'll check that hose tonight. I've just had another listen to the engine and when I blip the gas you can certainly hear more noises than normal, but there is also some funny deep burbling sounds as I come off the gas.

I don't appear to have any oil leaking from the gasket, however my friend's Megane (which I just used as a comparison) had traces of oil around the valve cover and a fair amount sitting on top of the inlet manifold tubes, so it looks like he's got that fault with his car. As least we've helped someone else's fault so far!
Renault Megane 1.6 - power loss. - doctorchris
Our Megane had the hose problem MM diagnosed, but when the car was only just over 1 year old the plug leads needed replacing as they were causing a misfire. These are quite expensive as Halfords listed replacement does not fit.
Renault Megane 1.6 - power loss. - Adam Going (Tune-Up)
Hi Dave,

Comments on MAP sensor hose very valid - have also come across a small brass restrictor inside the hose at the manifold end on some Renaults, and the hose had collapsed around the restrictor internally !

However, that aside, from your despcription of the fault, had you not already had a new Cat, I would have said "blocked Cat"!!
This could still be the case (not all that is new is good) or it could be a blockage further up the exhaust (possibly even debris from the old Cat). Inlet manifold vacuum is a useful guide - if vacuum drops away as revs are gently increased to around 3.5k it is an indication of possible restriction. In severe cases you may find that disconnecting the Oxygen Sensor and removing it (ECM will cope with this for test purposes)releases enough back pressure for perfromance to be restored or at least improved. This still does not tell you exactly WHERE the blockage is, and progressive removal or replacement of exhaust may be necessary.

Regards, Adam
Whatever is rightly done, however humble, is noble.
Renault Megane 1.6 - power loss. - davemar
When driving home the other evening, the power suddenly decided to restore itself, it felt like whatever was blocking the power suddenly become unblocked. Still, I decided to check things over when I got home.

The MAP hose was fine, but I found my exhaust manifold had a crack in it. This probably wasn't the cause of the significant power loss, but may have explained some of the noises. Anyway that should be easy to fix. But I didn't have time to give the inlet side of things a good look over. I'll certainly investigate this brass resistrictor, that sounds plausible. All the hoses I looked at seemed fine.

Renault Megane 1.6 - power loss. - davemar
I further checked various hoses connected to the inlet manifold and they all seemed fine, no splits or restrictions.

I tried patching up the crack on the exhaust manifold which seemed OK for a while but I suspect it didn't hold up. It was always going to be a short term fix while I track down a replacement part. I'm still lacking some power but I suspect this is down to the exhaust leakage now. There is certainly a little extra exhaust rasp and a lack of power at the top end. I ought to remove the exhaust system to double check no crap has ended up in there.


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