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nickjb
Joined: 13 Feb 2011 Posts: 58 Location: Bristol, UK
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Posted: Mon Jan 10, 2022 12:51 Post subject: 3.0 V6 misfire. What to try next? |
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Just picked up a 2004 3.0 V6 L400. It's low mileage in very tidy condition so should be great but it has a slight misfire. It stutters when going up mild inclines. Not badly but it is not right. It doesn’t happen when cruising, or on the flat, or when cold. If you boot it on a hill it'll kick down and run fine, it just seems to be when its straining a bit. There are some obvious potential causes of this but its had new spark plugs, HT leads, Ignition controller, Idle speed valve, Coil packs, Crank sensor, Cam sensor, Inlet manifold gaskets and the compression is fine. No fault codes showing on cheap BT reader. It is also duel fuel (petrol and gas) and it happens on both. Running out of thing to try so open to suggestions. |
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Posted: Mon Jan 10, 2022 12:51 Post subject: Google Ads keep this community free to join! |
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andyman
Joined: 08 Dec 2012 Posts: 5602 Location: Penrith
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Posted: Mon Jan 10, 2022 14:58 Post subject: |
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MAP or MAF sensor (or you may have both?) on the manifold. If they are dirty or failing, they can send bad data to the ECU. (I'm speaking generally here - no experience of the Mitsi V6). Usually, if you unplug them, the ECU will use default parameters, which, while they won't give optimal performance or economy, should make it all run smoothly, everything else being equal. Alternatively, try using hotter plugs - they cope better against fouling at low revs/higher throttle opening. _________________ Andy C L300 Super Exceed - over 100 smiles per gallon! |
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fintious
Joined: 24 Aug 2019 Posts: 173 Location: Doncaster
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Posted: Sat Feb 05, 2022 10:55 Post subject: |
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Auto transmission solenoid was the cause of mine doing that. Had a dry tie or something that was found after having the gearbox stripped down _________________ 3.0 V6, Auto. 2005 |
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nickjb
Joined: 13 Feb 2011 Posts: 58 Location: Bristol, UK
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Posted: Mon Feb 07, 2022 10:59 Post subject: |
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That does sound interesting. Can you elaborate a bit? Do you know which solenoid? Not sure what dry tie means. Thanks |
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JimboHS
Joined: 30 Dec 2021 Posts: 6 Location: Winchester
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Posted: Mon Feb 07, 2022 23:54 Post subject: |
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Hi Mine does exactly the same. Usually when going uphill at a steady speed between 25-35. At all other times it's fine. It seems like a misfire, but I also thought perhaps it was stuttering between gears. I have a 3Ltr V6 2004 Chamonix. |
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ChazK
Joined: 22 Mar 2021 Posts: 3 Location: Bridgwater
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Posted: Fri Mar 04, 2022 17:28 Post subject: |
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Anyone solved this yet. Mine does the same - I had the lock up clutch changed but made no difference. Occasionally it gets really bad where it won't accelerate and occasionally backfires. This has happened twice and when I take out the fuel filter, the petrol that's inside it is black. The new filter seems to cure it for a while and then it goes bad again. |
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grdelica123
Joined: 19 Jan 2020 Posts: 5 Location: Keighley
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Posted: Tue Apr 26, 2022 18:36 Post subject: |
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The only similar experience I had of erratic power loss on 2002 V6 was due to oil in spark plug wells. New rocker gaskets and plug gaskets solved it....mind you the there was plenty of evidence of oil in stone guard beforehand.
Got genuine Mitsi gaskets imported to solve it... a first attempt with generic gaskets still leaked. |
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lerxt335
Joined: 09 Nov 2020 Posts: 7 Location: Delabole
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Posted: Sun Jan 15, 2023 23:05 Post subject: |
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Did you solve the misfire problem? |
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dtnefish
Joined: 01 Aug 2020 Posts: 18 Location: Grassington
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Posted: Tue Feb 28, 2023 11:10 Post subject: |
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I have this problem too. I have had 2004 chamonix running fine for two years but last November it started behaving just like yours - very slight but noticeable misfire under load. I also have gas and it was doing it on both fuels. A test at Alljap motors (manchester) revealed two air pipes disconnected from throttle body. This appeared to fix it on petrol, so then I thought maybe gas system needs tuning. Bradford autogas could find nothing wrong but he tweaked it slightly and now its worse than ever on both fuels!
I have new plugs and leads to fit which is why I came on here. I gather it's a long job, expensive at garage, so I thought I would have a go myself. Any tips would be much appreciated.
Failing that, Map sensor and auto transmission solenoid sound interesting, although I am puzzled how anything in transmission could affect ignition? |
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lerxt335
Joined: 09 Nov 2020 Posts: 7 Location: Delabole
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Posted: Wed Mar 08, 2023 21:00 Post subject: |
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found the problem with my misfire or rather my local garage did, turned out that the rocker gasket had gone on the left bank causing oil to leak into the spark plug wells, a common problem with these engines apparently, then gaskets and seals go hard over time and fail. |
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dtnefish
Joined: 01 Aug 2020 Posts: 18 Location: Grassington
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Posted: Fri Mar 10, 2023 20:15 Post subject: |
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I seem to have solved my problem too. Someone suggested cleaning the MAF (mass air flow) sensor in the air intake. A squirt of electrical cleaner spray and a gentle rub with paper towel made no difference to its appearance but engine now purring again, even under load. One question, the delicate sensor doesn't look like any other one on Internet. Most are plastic and I think have a wire that does the sensing. Delicate is a wedge shaped stainless steel plate. Anyone know why it's different? |
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andyman
Joined: 08 Dec 2012 Posts: 5602 Location: Penrith
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Posted: Tue Mar 14, 2023 18:46 Post subject: |
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Pleased that for once, my random stab-in-the-dark suggestion seems to have worked for someone! _________________ Andy C L300 Super Exceed - over 100 smiles per gallon! |
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