Engine: 2.5: - Misfire?

Timmilne · Nov 8th, 2018, 21:44

My 850 20V Estate has developed a misfire, which was mild for a quite a while, then got worse, got much better after a good long thrash on the Motorway and has now suddenly gotten much more serious, to the point it feels terminal.

It's so hesitant that it requires extreme delicacy to get it moving (it's a Auto so options for added throttle are limited) and then misfires all through the rev-range, seriously down on power.

Any suggestions as to what it might be?

No Check Engine light

volvo again · Nov 9th, 2018, 15:32

First thing I would do is check condition of the plugs, when were they last replaced?
Is the misfire on one cylinder or more?
Need to check plugs HT leads ( I presume this model has a distributor) rotor arm & cap.

Bob Meadows · Nov 9th, 2018, 16:09

Symptoms sound to be a faulty rotor- so as above.
Bob

Luxobarge · Nov 9th, 2018, 16:48

Agree with above - distributor cap and rotor are not officially service items, so even a "full" service doesn't include them - but it should, especially on high mileage cars. Actually dizzy cap and rotor is the first thing I'd check personally, even before plugs - at least plugs do get changed periodically at service time.

Cheers!

capt jack · Nov 9th, 2018, 21:27

Take the dizzy cap and rotor off and give them a good clean. Then take the plastic top cover off the engine so that you can see all the plug leads. Run the engine after dark and watch for any stray sparks around any of the leads. When I had my V70 I found that the leads lasted about 100k miles, then started to break down.

Cheers

Jack

Nov 8th, 2018, 21:44	#1
Timmilne Member Last Online: Oct 9th, 2023 09:24 Join Date: Feb 2018 Location: London	Misfire? My 850 20V Estate has developed a misfire, which was mild for a quite a while, then got worse, got much better after a good long thrash on the Motorway and has now suddenly gotten much more serious, to the point it feels terminal. It's so hesitant that it requires extreme delicacy to get it moving (it's a Auto so options for added throttle are limited) and then misfires all through the rev-range, seriously down on power. Any suggestions as to what it might be? No Check Engine light

Nov 9th, 2018, 16:48	#4
Luxobarge Premier Member Last Online: Today 15:06 Join Date: Jan 2011 Location: Horne (Nr. Horley)	Agree with above - distributor cap and rotor are not officially service items, so even a "full" service doesn't include them - but it should, especially on high mileage cars. Actually dizzy cap and rotor is the first thing I'd check personally, even before plugs - at least plugs do get changed periodically at service time. Cheers! __________________ Some people are like Slinkies, they serve no useful purpose but they still bring a smile to your face when you push them downstairs.

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Nov 9th, 2018, 15:32	#2
volvo again Master Member Last Online: Yesterday 12:04 Join Date: Jun 2018 Location: Presteigne, mid Wales	First thing I would do is check condition of the plugs, when were they last replaced? Is the misfire on one cylinder or more? Need to check plugs HT leads ( I presume this model has a distributor) rotor arm & cap.

Nov 9th, 2018, 16:09	#3
Bob Meadows Premier Member Last Online: Today 10:13 Join Date: Sep 2017 Location: STANDISH LANCASHIRE	Symptoms sound to be a faulty rotor- so as above. Bob

Nov 9th, 2018, 21:27	#5
capt jack VOC Member Last Online: Apr 13th, 2024 20:27 Join Date: Jun 2006 Location: Selby, North Yorkshire	Take the dizzy cap and rotor off and give them a good clean. Then take the plastic top cover off the engine so that you can see all the plug leads. Run the engine after dark and watch for any stray sparks around any of the leads. When I had my V70 I found that the leads lasted about 100k miles, then started to break down. Cheers Jack

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