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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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How to diagnose a misfire....Views : 2409 Replies : 13Users Viewing This Thread : |
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Aug 28th, 2018, 14:17 | #1 |
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How to diagnose a misfire....
So I need some education again.....
Our V70 1999 2.4 non-turbo started a major misfire. One moment fine, the next hiccuping shaking and very rough running at all revs. The AA decided it needed all 5 coil packs replaced but could only get a single one from the local motor factors so swapped that into each plug in turn without it making much difference. Back home I put it on VIDA which shows ECM3503 and ECM3502 misfire on Cyl 1 and 2. The misfire count is the same on both if that means anything. It is the same with hot or cold engine So far I have dug out tools I haven't used since the days of carburettors and: -Done a compression test (consistent across all cylinders) -Swapped injectors around. The misfire stayed with 1 and 2. -Checked spark with a tester that shows the spark jumping a large gap on all cylinders. -Swapped plugs and also later put in an old set. No difference. -Swapped coil packs. Engine seemed to get a lot more rough with some swaps but VIDA still reported just 1 and 2 -Removed the wiring harness covering under the cam cover. All looks healthy -Checked coil pack earths on cam cover, all looks OK. So......what do I do next??? I'm not forgetting that the AA guy wanted to replace all coil packs but as they are all giving a healthy spark that doesn't seem right. Or can they be breaking down in some other way? Joe |
Aug 28th, 2018, 16:36 | #2 |
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Camshaft position sensor??
Had a similar problem on my old 2.0L 10 valve... |
Aug 28th, 2018, 21:02 | #3 |
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Hi Joe H,
Are "ECM-3503" AND "ECM-3502" the only active codes (in VIDA)? Are you sure it came all of a sudden? No poor fuel consumption, lack of power, hard starting etc? What make of plugs (current and the spare set) did you test with? Use Volvo. The turbo plugs are different from non turbo. It seems almost impossible that all coils have failed at the same time. And if they had, surely you wouldn't just get codes on cylinders 1 and 2. (And the car probably wouldn't run at all). Check that the wiring harnesses to the coils are good, and that the coils are bolted down (I think that is also a ground connection). Can you clear the codes? If you can, and swap coil 1 and 2 to say 4 and 5, then if those 2 coils are the problem, then when you run you should get new codes which correspond to the two new positions. Is there any small air hose near cylinders 1 and 2 which has perished or fallen off? I don't know about your particular car, but some of those 98/99 normally aspirated models had a small black rubber elbow underneath the cambelt end of the intake manifold, which perishes and allows excess air in. If you look carefully you might see it. Also see this old post https://www.volvoforums.org.uk/showthread.php?t=236453 Steve
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V70 2.5 Turbo AWD Man. 1999 Red V70 2.5 10V Auto 1998 Green C70 T 20V Auto Conv. 2001 Blue, C70 T5 Auto Conv. 2000 Blue V70 2.5 Turbo AWD Auto 1998 Green, V70 2.5 10V Auto BiFuel 1999 Red (scrapped) V70 20v Auto 1999 Green (scrapped) Last edited by SteveSarre; Aug 28th, 2018 at 21:05. |
Aug 28th, 2018, 21:04 | #4 |
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Also, see if the misfiring stops if you unplug the MAF .
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V70 2.5 Turbo AWD Man. 1999 Red V70 2.5 10V Auto 1998 Green C70 T 20V Auto Conv. 2001 Blue, C70 T5 Auto Conv. 2000 Blue V70 2.5 Turbo AWD Auto 1998 Green, V70 2.5 10V Auto BiFuel 1999 Red (scrapped) V70 20v Auto 1999 Green (scrapped) |
Aug 29th, 2018, 08:59 | #5 |
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Aug 29th, 2018, 09:17 | #6 | |||||||
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Thanks Steve - answers are:
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With coil packs moved to the other end of the engine it did not want to start - coughing and wheezing first but then ran with a similar misfire. The warning light does not come on the dash btw, although it sometimes flashes. Quote:
Quote:
Last edited by Joe H; Aug 29th, 2018 at 09:22. |
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Aug 29th, 2018, 09:18 | #7 |
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Aug 29th, 2018, 10:25 | #8 |
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Do you have an EGR on your engine?
Ensure it is clean and operating properly EGRs putting wrong amounts of exhaust gasses in the engine can upset the air/fuel mixture to a point that a misfire can result I've seen a very interesting video of exactly this on a Ford (I think) which resulted in intake manifold removal, then cleaning of all the EGR lines (some were totally clogged) to resolve the issue Once the EGR lines were clear and clean, the engine ran perfect with no misfires. Yes, I know the Volvo has a different EGR setup, but it's something worth checking.
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Aug 29th, 2018, 10:36 | #9 |
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The engine coolant temperature sensor can also cause problems with fuel mixture if it is failing.
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Aug 29th, 2018, 11:35 | #10 |
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See this nightmare thread
https://www.volvoforums.org.uk/showthread.php?t=61077 with a possible solution from Chris Rogers https://www.volvoforums.org.uk/showthread.php?t=62631
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V70 2.5 Turbo AWD Man. 1999 Red V70 2.5 10V Auto 1998 Green C70 T 20V Auto Conv. 2001 Blue, C70 T5 Auto Conv. 2000 Blue V70 2.5 Turbo AWD Auto 1998 Green, V70 2.5 10V Auto BiFuel 1999 Red (scrapped) V70 20v Auto 1999 Green (scrapped) |
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