V70 2.4 Petrol missfiring

[Snightlo]

Hello,
I just joined the Volvo community this month, by buying an old but seemingly reliable V70 from 98 with 210.000km on the clock. It had all the inspections done on time and just got through the German TÜV.

After some days of driving it, it startet to missfire briefly when stepping on to the accelerator. I am not an expert, but it feels like one cylinder is cutting out. This got a lot worse now. Last Friday after driving home around 30km and making a quick stop and then driving again it missfired the whole time.
Yesterday while driving to work it missfired most of the time and on the way back it did it all the time again after 15 km.

I checked the ignition sparks and every single one has a spark, so I guess there is no problem with the ignition system. New plugs are already ordered, as I got told it could be that the sparks are to weak for a proper ignition.

A friend of mine gave me his Bluetooth OBD2 Connector to check for Error Codes. I tried 3 different Apps but it could not connect, with the ECU.

Do you guys have any suggestions, about the error it self, or a proper way to connect to the OBD 2?

If you need more informations let me know.

[4x4]

When was the fuel filter last changed?

[Snightlo]

I dont know that, all the inspections have been done on time. Is it part of the inspection cycle? I can check the service booklet tomorrow for that

[Luxobarge]

Very likely that it's simply one of the coils is failing - this engine has separate coils for each plug. See if you can identify which cylinder is misfiring, then swap that coil for another one and see if the fault moves to the other cylinder. It probably will. Replace the coil on the cylinder that's misfiring and it'll be fine.

How do you tell which cylinder is misfiring? ideally, reading the codes will tell you, but I see you're having trouble with the code reader. Another method which I have used very successfully is to use an infra-red temperature gauge, like a gun with a red laser dot that you point at the object and it gives a temperature reading. Point this at the relevant cylinder (or ideally the exhaust manifold) and one will be reading cooler than the others. Other folk on here might come up with other suggestions, such as running it for a while and inspecting each spark plug, although that's quite laborious.

Just one word of warning - if I were you I wouldn't drive the car for long with a misfire. The reason is that the unburned fuel will ignite in the catalytic converter and raise its temperature quite a lot. Catalytic converters already run very hot, and if they get much hotter they will break down internally and collapse, so running with a misfire (especially if you're using a lot of power) gives a high risk of costing you a new catalytic converter. It's OK to run it for diagnostic purposes, but I'd keep it to that if I were you.

[SteveSarre]

Hi Snightlo

If it is a 1998, it will have a single coil and a distributor cap and rotor arm. I would inspect the tip of the rotor arm and the posts in the distributor cap. Scrape off any corrosion or replace if necessary.

Here are some links to Skandix in case you are in Germany (but you should check for your specific car),

https://www.skandix.de/en/spare-part...r-cap/1009698/
https://www.skandix.de/en/spare-part...butor/1009699/

The ignition cables could also be starting to fail. If they are original, the year of manufacture is printed on each cable.
https://www.skandix.de/en/spare-part...cable-kit/764/

If you remove the black top cover (Torx screws) then when it is misfiring, you could unplug each ignition cable in turn (pull on the boot not the cable), and see which cylinder is not having any effect.

It would be easy to do this before you replace the spark plugs, which are under that same top cover.

Hope that helps,
Steve

[Snightlo]

It has a single Coil, the seperator is looking very new and got replaced a short time ago I recon.

The new Spark Plugs have arrived and I screwed them in. It is running very smooth now. I took it to a short drive and it run very well. I guess the sparks werent reliably igniting anymore, and or were not realy suited for the car.

None the less, thank you all for your suggestions. I would have tryed them out, wouldnt it have not been solved with that.

[JohnM 855 T5R]

Originally Posted by Snightlo

It has a single Coil, the seperator is looking very new and got replaced a short time ago I recon.

The new Spark Plugs have arrived and I screwed them in. It is running very smooth now. I took it to a short drive and it run very well. I guess the sparks werent reliably igniting anymore, and or were not realy suited for the car.

None the less, thank you all for your suggestions. I would have tryed them out, wouldnt it have not been solved with that.

5-cylinder Volvos do seem to be very sensitive to plug wear and plug gaps. From my own experience with high mileage Volvos, misfires of the type you described are almost always due to a plug problem. Forget what the service schedules say, change them every 25,000 miles / 40,000 Km at the most. Plugs are cheap enough to make this a sensible precaution. Also, use a top quality plug - Volvo, NGK or Bosch platinum.

Regards
John