Engine misfires normal or not?

[innocent2k]

This is a generic petrol question, but did not find a generic petrol forum so posted under the car I'm questioning.

I'm confused as to whether or not any number of cylinder misfires may be normal. Some say that any number of misfires indicate a problem that need to be addressed, and some say it's fine as long as it's evenly distributed by cylinders. Both statements can't be true

I'm asking because I still have the odd issue with my VEA engine. Twice it just started misfiring like crazy for no obvious reasons, just to be fine the next day. This is obviously of concern, which is why I'm wondering if seeing 2-5 misfires on each cylinder during a trip is normal. If it is, I can take that out of the equation.

When it misfired like crazy (at least the last time when I got a readout before someone cleared the codes) it was only one cylinder that acted up.

Spark plugs are new. Coils are not.

[Norcat]

You should have the engine fault light on if its misfiring as this will throw the oxygen content out of spec in the exhaust gases. You need to investigate this as driving with a misfire can damage the catalytic converter requiring a new one£££
If its an ignition problem it will then dump unburnt fuel into the exhaust, if its an injector problem then lack of fuel will show excess oxygen so the ECU will go rich on the other cylinders to try and pull the O2 down, either is bad for the converter.
I would replace the coil first in view of your post, any misfire is not normal.

[innocent2k]

Originally Posted by Norcat

You should have the engine fault light on if its misfiring as this will throw the oxygen content out of spec in the exhaust gases. You need to investigate this as driving with a misfire can damage the catalytic converter requiring a new one£££
If its an ignition problem it will then dump unburnt fuel into the exhaust, if its an injector problem then lack of fuel will show excess oxygen so the ECU will go rich on the other cylinders to try and pull the O2 down, either is bad for the converter.
I would replace the coil first in view of your post, any misfire is not normal.

The CEL is only lit when it goes totally crazy (as in constant misfiring), the others are just occasional misfires. For the CEL to be lit it requires more than occasional misfires. When CEL was set only a "cylinder 4 misfire" code was set. So, this still leaves me with the question, should I expect misfire count to be 0 after a trip of, say, 20 minutes? If I should expect that, this is clearly a case for the dealership I bought the car from because of the Norwegian consumer laws.

[Norcat]

Seems you are not too far from me, definitely use the kjøpsloven and go back to the dealer.

[innocent2k]

Originally Posted by Norcat

Seems you are not too far from me, definitely use the kjøpsloven and go back to the dealer.

What is stopping me from it is that I'm still trying to figure out if occasional misfires are to be expected or an anomaly. Bought the car in Fetsund so there's a bit of distance. What also annoys me a bit is how vague Volvo is with their response when I ask.. "It may or may not be normal, if no error codes probably fine"-kind of response :P

[Chrisv60]

I can see how a minor glitch might result in a technical misfire, but surely a misfire that you can feel is unacceptable. I've had many diesel and petrol cars over the years and the only time I've felt a misfire is when there's something obviously wrong such as a faulty coil or spark plug.

If you are just seeing the count through the OBD then unplug the reader, forget anbout it and continue to use the car unless or until it throws up an engine light.

If it's a perceptible misfire whilst driving this has got to be unacceptable and I would be taking it to the dealer or elsewhere for diagnosis.

[innocent2k]

Originally Posted by Chrisv60

I can see how a minor glitch might result in a technical misfire, but surely a misfire that you can feel is unacceptable. I've had many diesel and petrol cars over the years and the only time I've felt a misfire is when there's something obviously wrong such as a faulty coil or spark plug.

If you are just seeing the count through the OBD then unplug the reader, forget anbout it and continue to use the car unless or until it throws up an engine light.

If it's a perceptible misfire whilst driving this has got to be unacceptable and I would be taking it to the dealer or elsewhere for diagnosis.

Well, as I tried to explain, but maybe not well enough...

I do see non-noticeable misfires every trip with an OBD-reader. This does neither set CEL or any other error codes. Occasionally (twice so far) I've had a real misfire-o-rama that would just not stop even if I tried re-starting the car. Next day it would just be gone by itself.

So, my reason for asking if it should be expected zero misfires or not, is because I want to know if there's somehow a connection between the really bad random cases and what I'm observing with an OBD monitor. Some claim any number is a sign of something wrong while others say it's normal. I still try to find out what statement is the correct one so I know what path to chase

Ever so often the car will be jerky for about 3-4 seconds, then it'll clear out by itself. This does not set any codes either.