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Discussion Starter #1
Please help - My Smart started misfire 1500km ago with engine misfire on cylinder 1 - replaced all 6 plugs, plugs on cylinder 1 was totally carbonded up the rest was like new. Engine started misfire again, the funny thing this time is when you switch the engine off and start again it runs fine for a few minutes and starts misfire again - thought it was the same, took out the plugs - this time the top plug of cylinder one was burned away, bottom plug had a bit of carbon but was fine. Replaced the plugs. Every time you Start the engine - same thing, runs fine for a few minutes then start misfire and loose power. :shrug::shrug: Can it be the injector?
 

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You might try a good strong dose of combustion chamber cleaner like Marvel Mystery Oil or Seafoam. Looks like you are deposit following one of the spark plugs on cyl. #1. A compression test followed up by a cylinder leakage test may also be useful in diagnosing your concern.
 

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You might try a good strong dose of combustion chamber cleaner like Marvel Mystery Oil or Seafoam. Looks like you are deposit following one of the spark plugs on cyl. #1 . A compression test followed up by a cylinder leakage test may also be useful in diagnosing your concern.
Bob gave my 2013 a double shot of that "Marvel Mystery Oil" - when my smart got a misfire on #1 . --> IT WORKS...
 

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Discussion Starter #8
I am back - Unfortunately we can not get Marvel Mystery Oil or Seafoam in New Zealand but used "Nulon combustion cleaner - apparently the best in NZ". Still the same - running perfect when it is ideling up to +-3000rpm then starts to misfire on no1. Replaced the No1 injector - this did not help ither. I will do a compression test as soon as I get a compression tester.

Any other suggestions??
 

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I had a ' misfire on cyl 3' which turned out to be on cyl 1. A compression test showed a low compression on cylinder #1 .
 

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Discussion Starter #12
I was away for a few days - Tried the following the last 2 days. Got a compression test done - the compression on all three cylinders are very close. Swopped the coil packs. Now I got a code saying misfiring on multiple cylinders, thought I have the problem - bought a coil pack and replaced the one I thought was the culprit, still the same. Replaced plug wires, no change. Let me just tell you guy's again what it is doing - Start the smart - run on idle no problem, runs as smooth as can be ( left it to run for half an hour on idle - no problem) - floor it till ref limiter kicks in and keep it there, no problem – let it return to idle – no problem. Press the petrol pedal to about 2000rpm, then the problem start (starting to misfire). Something else I tried – switching the ignition off and on again while it is misfiring, guess what the misfire disappears and runs smoothly on idle but the moment you slowly ref it up again it starts to misfire on about 2000rpm. (Done this a few times, the same outcome). Just a stab in the dark – isn’t there may be a sensor somewhere that can do this?
 

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YellowSmart, I fought the same problem on my 451. I ran combustion cleaner through it, switched the coils and replaced the spark plugs, but still had the same symptoms as you, only mine was problematic on cylinder 3. It's a very strong possibiility that you have a burned valve. A valve that gets gummed up with carbon between it's face and seat won't be able to sit on it's seat to cool. The valve transfers it's heat to the seat as it is seated, reduce that "seat time" and the valve and or seat will burn and the only remedy is to replace the burned valves and get the seats reground. Usually with burned valves, the heat on the valve and stem will also cause the valve guides to wear out and that causes the valves to even more so not seat properly. One condition aggrevates the other no matter how you look at it. So find a compression gauge and do a compression test and that will pretty much tell the tale as the old saying goes. I removed my head and had an automotive machine shop recondition my head with new valves and guides and now I use Marvel Mystery oil in my engine oil and all has been good. I wish you luck. DCO
 

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Discussion Starter #14
Thanks DreamCarOwner - I have done a compression test and no problems.
I must have a Gremlin somewhere but that is the question????
 

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I know that it's a 450 and I surmized that from the mention of 6 spark plugs. I had not read post #12 when mine posted as #13 or my answer would have been different. Before reading #12 I was thinking along the lines of a mechanical problem with the engine. But after reading 12.......
 

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Like I said, 450 with the Mercedes motor...
Which were know to have head problems....

MB replaced a lot of them in Europe under warranty.

Even though it is a different engine, after the experience with my Dad's smart, I would say you are losing compression once it warms up. Dad's 451 did the same thing, would idle fine, and run fine when first started, then after it warmed up it would pop a misfire code. Ended up being both burnt valves, and a scored cylinder...:(

We installed a 20K mile replacement motor, and it's been perfect since...
 
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