Running rough under load

baglartimus · Oct 14th, 2014, 12:48

My 1999 V70 2.5 10 valve, has just started running roughly when the engine is under load. When stopped, it idles ok, but vibrates badly when you blip the throttle. When driving, and I floor the throttle, it vibrates badly, feeling like its not running on all five cylinders. Once the engine revs build up, it runs smoothly. If I accelerate very gradually, then the engine behaves.
There are no warning lamps on.

Any ideas what this could be?

I was suspecting it might be an ignition fault, so took out all the spark plugs and examined them. They all look ok, with no signs of tracking. I have also checked the distributor cap - this was a bit dirty looking, so I cleaned this up. The coil and ignition leads all look ok. The cleaning of the distributor cap has made no difference to the rough running.

I have ordered new ignition wires, coil, distributor cap and rotor arm, as I think the originals may be getting a bit past it.

kevvydude · Oct 14th, 2014, 13:59

hi, i had this a few weeks ago, fitted new leads and it sorted it, the old leads looked ok but they where naff, i brought very good leads ,and the O is runnig perfect now

kevvydude · Oct 14th, 2014, 14:06

also i woulnd,nt buy aftermarket dizzy cap or rotor arm,as they just are,nt built like volvo stuff, just my opinion ,i brought a after market temp sensor and the car just would,nt get up to temp,and the mpg dropped by 4 mpg,brought a volvo one and back to 30 mpg pottering around, so i stick with original now

SwedishBus · Oct 14th, 2014, 19:46

New leads with careful attention to the routing and clipping around the top of the engine should do it.

The ignition breaks-down under load, which is why the engine only shakes with the throttle open; the voltage to get the spark underway is forced to rise, and gets to the point where a lead or distributor cap will track down to earth. If you have a lean mixture on one cylinder, this will exacerbate the issue, as the kV on that cylinder will rise accordingly to achieve the necessary ionisation.

If you get a repeat problem on that one cylinder, might be worth checking the fueling

Luxobarge · Oct 14th, 2014, 21:17

Just for fun, take the spark plug cover off and run the engine in the dark, see if you can see any stray sparks. I'd lay money that you will, if the leads or other HT components are past their best, and this is an indicator of problems - there should be no sparks at all. I've had cars that showed a right fireworks display under there in the dark, but still weren't (yet) having any running problems.

baglartimus · Oct 15th, 2014, 09:39

Quote:

Originally Posted by Luxobarge

Just for fun, take the spark plug cover off and run the engine in the dark, see if you can see any stray sparks. I'd lay money that you will, if the leads or other HT components are past their best, and this is an indicator of problems - there should be no sparks at all. I've had cars that showed a right fireworks display under there in the dark, but still weren't (yet) having any running problems.

Thanks, I will give this a try tonight. I am still waiting for my new ignition components to arrive from Germany.

baglartimus · Aug 7th, 2015, 14:03

I didn't bother with the test in the dark in the end, I just replaced distributor cap, spark plugs, ignition coil, and ignition harness, and this fixed it.

SteveSarre · Aug 7th, 2015, 16:34

If you swap your old coil back in, and it still runs OK, then you've got a spare coil which works, which is good to have.

Steve

baglartimus · Aug 8th, 2015, 10:14

Sadly I no longer have the car, so can't try swapping the old coil back in.
Thanks,
Simon

Oct 14th, 2014, 12:48	#1
baglartimus New Member Last Online: Aug 28th, 2019 10:42 Join Date: Oct 2014 Location: Stockport	Running rough under load My 1999 V70 2.5 10 valve, has just started running roughly when the engine is under load. When stopped, it idles ok, but vibrates badly when you blip the throttle. When driving, and I floor the throttle, it vibrates badly, feeling like its not running on all five cylinders. Once the engine revs build up, it runs smoothly. If I accelerate very gradually, then the engine behaves. There are no warning lamps on. Any ideas what this could be? I was suspecting it might be an ignition fault, so took out all the spark plugs and examined them. They all look ok, with no signs of tracking. I have also checked the distributor cap - this was a bit dirty looking, so I cleaned this up. The coil and ignition leads all look ok. The cleaning of the distributor cap has made no difference to the rough running. I have ordered new ignition wires, coil, distributor cap and rotor arm, as I think the originals may be getting a bit past it. __________________ Current: V70 SE 2435cc petrol 2005, Metallic Green Previous: V70 2.5 10V XLT 1999, Silver

Oct 14th, 2014, 13:59	#2
kevvydude Premier Member Last Online: Nov 9th, 2017 22:33 Join Date: Oct 2007 Location: Aldershot Hampshie	hi, i had this a few weeks ago, fitted new leads and it sorted it, the old leads looked ok but they where naff, i brought very good leads ,and the O is runnig perfect now __________________ a clean car requires a certain amount of mental illness ʎɐqǝ uo pɹɐoqʎǝʞ ɐ ʎnq ı ǝɯıʇ ʇsɐן ǝɥʇ sı sıɥʇ

Oct 14th, 2014, 14:06	#3
kevvydude Premier Member Last Online: Nov 9th, 2017 22:33 Join Date: Oct 2007 Location: Aldershot Hampshie	also i woulnd,nt buy aftermarket dizzy cap or rotor arm,as they just are,nt built like volvo stuff, just my opinion ,i brought a after market temp sensor and the car just would,nt get up to temp,and the mpg dropped by 4 mpg,brought a volvo one and back to 30 mpg pottering around, so i stick with original now __________________ a clean car requires a certain amount of mental illness ʎɐqǝ uo pɹɐoqʎǝʞ ɐ ʎnq ı ǝɯıʇ ʇsɐן ǝɥʇ sı sıɥʇ

Oct 14th, 2014, 21:17	#5
Luxobarge Premier Member Last Online: Today 14:30 Join Date: Jan 2011 Location: Horne (Nr. Horley)	Just for fun, take the spark plug cover off and run the engine in the dark, see if you can see any stray sparks. I'd lay money that you will, if the leads or other HT components are past their best, and this is an indicator of problems - there should be no sparks at all. I've had cars that showed a right fireworks display under there in the dark, but still weren't (yet) having any running problems. __________________ Some people are like Slinkies, they serve no useful purpose but they still bring a smile to your face when you push them downstairs.

Aug 7th, 2015, 14:03	#7
baglartimus New Member Last Online: Aug 28th, 2019 10:42 Join Date: Oct 2014 Location: Stockport	Replaced all ignition components I didn't bother with the test in the dark in the end, I just replaced distributor cap, spark plugs, ignition coil, and ignition harness, and this fixed it. __________________ Current: V70 SE 2435cc petrol 2005, Metallic Green Previous: V70 2.5 10V XLT 1999, Silver

Oct 14th, 2014, 19:46	#4
SwedishBus Member Last Online: May 5th, 2024 21:50 Join Date: Oct 2014 Location: Isle of Skye	New leads with careful attention to the routing and clipping around the top of the engine should do it. The ignition breaks-down under load, which is why the engine only shakes with the throttle open; the voltage to get the spark underway is forced to rise, and gets to the point where a lead or distributor cap will track down to earth. If you have a lean mixture on one cylinder, this will exacerbate the issue, as the kV on that cylinder will rise accordingly to achieve the necessary ionisation. If you get a repeat problem on that one cylinder, might be worth checking the fueling

Aug 7th, 2015, 16:34	#8
SteveSarre Premier Member Last Online: Today 10:40 Join Date: Oct 2004 Location: London/West Country	If you swap your old coil back in, and it still runs OK, then you've got a spare coil which works, which is good to have. Steve __________________ V70 D 5244 T (E4 engine) 2401cc 163HP manual 2006 blue V70 2.5 Turbo AWD Man. 1999 Red C70 T5 Auto Conv. 2000 Blue V70 2.5 Turbo AWD Auto 1998 Green

Aug 8th, 2015, 10:14	#9
baglartimus New Member Last Online: Aug 28th, 2019 10:42 Join Date: Oct 2014 Location: Stockport	Swapping in old coil Sadly I no longer have the car, so can't try swapping the old coil back in. Thanks, Simon __________________ Current: V70 SE 2435cc petrol 2005, Metallic Green Previous: V70 2.5 10V XLT 1999, Silver

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