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850 / S70 & V70 '96-'99 / C70 '97-'05 General Forum for the 850 and P80-platform 70-series models |
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Running rough under loadViews : 1125 Replies : 8Users Viewing This Thread : |
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Oct 14th, 2014, 12:48 | #1 |
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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.
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Current: V70 SE 2435cc petrol 2005, Metallic Green Previous: V70 2.5 10V XLT 1999, Silver |
Oct 14th, 2014, 13:59 | #2 |
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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
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Oct 14th, 2014, 14:06 | #3 |
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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
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Oct 14th, 2014, 19:46 | #4 |
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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 |
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Oct 14th, 2014, 21:17 | #5 |
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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.
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Oct 15th, 2014, 09:39 | #6 | |
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Sparks in the dark
Quote:
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Current: V70 SE 2435cc petrol 2005, Metallic Green Previous: V70 2.5 10V XLT 1999, Silver Last edited by baglartimus; Oct 15th, 2014 at 09:43. Reason: To add the subscribe option |
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Aug 7th, 2015, 14:03 | #7 |
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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.
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Current: V70 SE 2435cc petrol 2005, Metallic Green Previous: V70 2.5 10V XLT 1999, Silver |
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Aug 7th, 2015, 16:34 | #8 |
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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
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Aug 8th, 2015, 10:14 | #9 |
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Swapping in old coil
Sadly I no longer have the car, so can't try swapping the old coil back in.
Thanks, Simon
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Current: V70 SE 2435cc petrol 2005, Metallic Green Previous: V70 2.5 10V XLT 1999, Silver |
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engine, load, misfire, rough |
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