Hello all,
Not so much a question just a story. Get in the car before, drive off out of the estate and I think to myself, "running a little rough today". Get onto a main road, open her up....nothing. Second gear, running like a tractor. Very odd. Carry on for 10 seconds and as the road inclines, the car...declines. Pull over, turn the engine off and checked for any fault codes. None. Start up, save thing. Really rough, rev and the entire car shakes. "This can't be good Adam" says I - but I can't stay where I am because I'm on a main road.
I initially think, Cam belt but then realise the car woulnd't go at all. So I turn into a side street, turn off again, no warning lights. Check engine temp, fine. I know all the fluids were ok as I checked them just yesterday. Give Dad a ring and ask, should I take it home? He says yes, so I crawled home at little more than 20 mph, sounding like the engine out of a Massey Ferguson and back into the drive with the car shaking like mad. Get out and can instantly smell rotten eggs. "The Cat!" I think. Nothing seems out of place so I rev the engine slightly and you can hear a rattle when you rev it.
Dad gets home and confirms my suspicions about the cat so the car is now parked on the drive, undriveable until we sort a cat out tomorrow. A shame as I'd done a full valet on it the other day!
Has anyone heard of the cats going so early on Focuses...Foci? Is it really that early or is 66k normal?
Cheers
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Adam
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Adam,
I always thought a sudden collapse of the catalyst would be uncommon due to their location at the front of the exhaust system, therefore they don't get corroded like the rest of the system does. How do you know it's the cat? Is there physical damage? It could be that a baffle has collapsed in the middle or back mufflers, causing a blockage and hence the reduction in power. But this wouldn't cause any problems at idle.
[GUESS MODE]
If you're getting fumes out the exhaust then I doubt there's a blockage, nor it's the cat that's causing it. As it's also happening at idle I would suspect an unrelated serious misfire problem.
[GUESS MODE OFF]
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Mike Farrow
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Your guess is as good as mine. I just smelt rotten eggs and assumed the cat as did Dad.
At idle, you wouldn't know anything was wrong. Touch the throttle and it judders quite badly. Rev it a little harder and it seems to go ok but when you move it's very, VERY bad. It jerks pretty much all of the time and there's very little power.
Add to this that I have to drive it to a garage a good 20 miles away tomorrow.
Looks like I'll be doing a lot of pulling over!
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Adam
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Sounds more like gasket/joint failure around front pipe area.Again just a guess??
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Steve
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That doesn't sound too good Steve!
I'm hoping to take it into the garage tomorrow so I'll report back tomorrow night.
Thanks for your replies,
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Adam
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On reading further.I doubt exhaust.Something else??.Will await your reply!
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Steve
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Doubt its an exhaust problem. Lack of power plus H2S smell (rotten eggs) points to unburnt fuel in the exhaust - suspect some kind of engine or engine-management fault. Possible over-fuelling or ignition fault.
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H2S smell (rotten eggs) points to unburnt fuel in the exhaust
I was thinking that's what rotten egg smell always was but wasn't sure, thanks for confirming!
We told you it was swallowing too much fuel Adam :-)
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Mike Farrow
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Uh-oh. I'm really not liking the sound of that!
I'd ask if it's ok to drive but I have no other choice getting it to this garage.
I should be taking it after Uni so I may have an idea later on.
I'll report back tonight.
Thanks again for help.
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Adam
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I've just taken it around the block and I'm tending to agree it isn't the exhaust. Now I'm not a mechanic but hear me out.
It's very bad when you move off - at around 1500 revs. Once you're moving it's still jerking.
However,
when you rev it up to around 3,000 you wouldn't think anything was wrong. At around 1200 revs in neutral it's quite bad though.
Now my thinking is, if it was the cat - or the exhaust blocked in general, surely it would be worse the higher the emissions - i.e. - the higher the revs?
I'm just guessing now and there's no point but I like to put ideas forward!
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Adam
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Now my thinking is, if it was the cat - or the exhaust blocked in general, surely it would be worse the higher the emissions - i.e. - the higher the revs?
Correct.
Any problem you have won't show up at 3000rpm because at that speed the dynamics of the engine prevent you feeling any vibration. I suspect the problem's still there at that speed though.
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Mike Farrow
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The car is fixed.
It was....
....the coil pack. A common fault apparently.
Many thanks for you help - very much appreciated.
Cheers,
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Adam
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Don't have the foggiest. I'm picking it up tomorrow so I'll find out the damage then!
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Adam
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It was.... ....the coil pack. A common fault apparently.
Curious, how can a broken coil pack cause problems all the time except at idle?
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Mike Farrow
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Got it back today Runs absolutely fantastic! They also solved the handbrake problem. Turns out the back brakes were sticking. I think we've found my fuel consumption problems!
Again, many thanks for the help. Very much appreciated.
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Adam
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When at idle there isn't much pressure in the cylinder at ignition time, so the air/fuel mixture is not very dense, therefore the resistance path to the spark is relatively low. There is also more time to build up the electrical tension in the coil. When the engine is called upon to work, ie throttle opened, more mixture, more pressure, more resistance and the coil cries enough. At higher revs, less time between sparks as well.
The last point, coil tension, I don't think applies as much with modern management systems.
Hope this helps.
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Thanks mjm - that's explained it clearly for me!
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Adam
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The dwell time (coil primary 'on' time) is constant in most modern ignition systems (hence they're termed 'constant energy' ignition systems). The main reason that HT fails under load is the higher cylinder MEP and gas density under open-throttle low-rpm conditions.
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I think you should all open up a "Backroom" chain of garages.
The knowledge on here astounds me sometimes.
By the way - thanks again!
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Adam
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Thanks, Aprilia, I thought I had read something about the constant current system somewhere, hence rpm is a little irrelevant.
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