Automotive

Misfire/cat damage - how quick?

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  • Oct 18th, 2015 1:22 pm
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[OP]
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Dec 8, 2010
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Misfire/cat damage - how quick?

Ok, so I did something stupid. You live and learn, looking for some advice.

Car was running rough, cleaned MAF sensor which I thought helped/fixed. Went on a trip, realised part way through that car was still running rough. I should've turned around there and then, oh well.

Continued on to destination - car is rough going up hills in highest gear but seems ok if you put foot down a bit. No CEL at this point.

Arrive at destination. Do research on phone, figure it's probably ignition coil - car has 4.6l Ford V8.

Two days later, start car to go home - thanksgiving holiday Monday - CEL flashes then goes solid. Silly me didn't realise *flashing* is the worst. Drive home, pull codes - cylinder 7 misfire plus P0316, misfire on start.

Car hasn't moved since but did 230km with CEL on. Again, you don't need to tell me I'm stupid for having driven the car, I've worked that out.

Car's a Crown Vic. Reading around, it seems there will be an O2 sensor code if I'd trashed the catalytic converter - right or wrong? Car was struggling uphill before any CEL came on.

Also, looks like my car has dual dual cats (two pipes, each have two cats) - if I have trashed something, will I likely have only trashed one pair, or both? It's single exhaust pipe if that matters.

New coils are on their way. I guess when I put one in and clear the codes I'll see if I still have low power.

If I don't replace the cats, presumably I can still drive around town? Car doesn't get much use anyway. Any downside to driving it assuming the cat isn't completely clogged?

I don't need to pass an etest, though obviously don't want to pollute. Presumably the non-NY/CA cats will do for here?
12 replies
Deal Expert
Aug 22, 2011
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Ottawa
Who cares about the cats, just go with straight pipes.
If changing the coils, clears the CEL, you have no problems for the next etest.
Deal Fanatic
Aug 15, 2015
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ON
If you did cause any damage it will be only on the cat connected to that missfiring cylinder . Other side will be fine.
Member
Aug 25, 2011
284 posts
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Toronto
What makes you think you damaged your catalytic converter?
Can you be more clear about struggling to go uphill?
Was your car low on power overall?
Or was it more like you felt your engine stuttering/misfiring?

If your engine is stuttering/misfiring, it could be either fuel injector, spark plug, or coils. You could try swapping the injector or spark plug with another cylinder to see if the CEL follows the that part. like, swap cylinder 7 & 8 injectors. If CEL then reads cylinder 8 misfire, then you know it's the injector. You can also do a visual check of the spark plugs to see if they have fouled.

If your car is down on power overall, it could be the sign of a plugged catalytic converter. Certain cars come with ceramic cats instead of metal. If you have ceramic pre-cats, any excess oil and fuel in the exhaust can foul the ceramic, causing it to disintegrate and plug up the main cat down stream.

But yes, start with fuel injectors, plugs, or coils first.
Member
Aug 25, 2011
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Toronto
vkizzle wrote:
Oct 17th, 2015 5:48 pm
Who cares about the cats, just go with straight pipes.
If changing the coils, clears the CEL, you have no problems for the next etest.
Not necessarily. If the mechanic/service advisor can smell that you are running catless(and it's noticeable), he can fail you even without any CELs.
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Aug 22, 2011
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gotrice111 wrote:
Oct 18th, 2015 10:30 am
Not necessarily. If the mechanic/service advisor can smell that you are running catless(and it's noticeable), he can fail you even without any CELs.
That's why you go one of the quick oil change shops.
Not one person working there is a license mechanic, therefore has no qualifications to identify as such.
[OP]
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Dec 8, 2010
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No etest where I am.

Spark plug looks ok. Coils are known on this engine, there is a crack across the top of the coil so I think it's that.

No cat codes. Low power up hill - in top gear it will drop from 100 down to 80 then kick down a gear. Cannot maintain 100 kph in top going up reasonable hills (Mont Tremblant-Ottawa, so not BIG hills, but not gentle flat country either). In third it can do it.

I guess I'll see what happens when I replace the coil.
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Feb 6, 2011
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When the check engine light flashes, it indicates a type A misfire which can damage the exhaust, cat convertor due to raw fuel overheating. The system can disable offending injector to prevent raw fuel from passing through the exhaust to prevent further damage. But if the injector is stuck on for whatever reason there will be cat damage.
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vkizzle wrote:
Oct 18th, 2015 10:38 am
That's why you go one of the quick oil change shops.
Not one person working there is a license mechanic, therefore has no qualifications to identify as such.
If they are not licensed/qualified, stay away.
[OP]
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billford wrote:
Oct 18th, 2015 12:40 pm
When the check engine light flashes, it indicates a type A misfire which can damage the exhaust, cat convertor due to raw fuel overheating. The system can disable offending injector to prevent raw fuel from passing through the exhaust to prevent further damage. But if the injector is stuck on for whatever reason there will be cat damage.
Ok, so hopefully the fried coil led to the car's computer disabling injector 7, all good?
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daverobev wrote:
Oct 18th, 2015 12:56 pm
Ok, so hopefully the fried coil led to the car's computer disabling injector 7, all good?
That's the way its supposed to work...
Fix whatever caused the misfire, clear the codes, drive it and see what happens...

Also, if the spark plugs are old/worn, they can also damage coils.
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Aug 22, 2011
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billford wrote:
Oct 18th, 2015 12:46 pm
If they are not licensed/qualified, stay away.
None of the quick lube places are.
For a quick 10min etest...I'm confident to get it done there.
Penalty Box
Oct 17, 2012
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how old is your vehicle

have the same code the reason causing the problematic code b/c my dash board required fix or repair

misfire 2 and misfire 5 and when accelerating the gas clogged up

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