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Discussion Starter #1
I have just over 100k on my smart. it is running like the day I got it except for start up in the 40-60 deg F days. On cold start up the secondary air injector whine is there but only after a squawky start up. when this happens it misses a bit and the check enjine light comes on with the misfire cylinder 2 code. sometimes it will go into limp mode. ( have to stop and restart then all is fine) not sure what to do to fix it. I think the Air Injector motor will smooth out. It could be stiff from the long warm summer.
 

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is the injector motor "user serviceable" like the heater blower motor? i did clean the blower motor a few years ago and that gave it a few more years of service. i did buy a new one, will probably install it later this month before winter sets in.
 

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Tucker's engine has pretty much always missed in the Winter, just never enough to trigger limp mode or a CEL. It only threw limp mode once, and that was the last time it ever missed in the Winter.

I was under the assumption Wintertime missing was a thermostat issue. It could also be that one of the cylinders (it's not always the one indicated on the CEL) has really low compression while cold.
 
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Sounds similar to my old 2009, It got better when I put new coils on, but after 3 years, (and 146,000 miles) it ended up with a burned valve. Marvel Mystery Oil does help.
 

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I would suspect a burned valve. Mine ran fine in warm weather and I would have never suspected a problem if it were not for the CEL. Then as the weather started to get colder I noticed it starting to run rougher until the engine warmed up. The valves in this engine are so small that a hot spot on a valve face can rapidly heat up the valve enough to cause problems. The valves in my 20 hp riding lawn mower are larger than the valves in the Smart but the rider has 2 valves whereas the Smart has 4. They cram 4 valves per cylinder and there just isn't any extra room in the combustion chamber. Just get out that trusty old compression gauge and that will tell the tale. Then get on ebay and look up Mollies Classics and order the kit. My biggest surprise of the entire head rebuild was before the rebuild even with a hairy valves on cylinder 3 I was still squeezing 43 MPG out of it. After I put it back together my mileage dropped to 33 MPG. That's a huge drop and I thought I had not done something right. But after 1200 miles it's back up to 38 to 39, so I hope the valve guides will loosen up to spec and I can get back to 43. It did improve the power output noticably. It wasn't enough to pull the front wheels off the ground on a green light, but that would probably scare me too much anyway. (not). DCO
 

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I changed Tucker's plugs and misfires were still happening, then put in some MMO, no more misfire. But of course, it's still warm-ish outside. I reckon he will not be having fun trying to run in the Winter.
 

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Discussion Starter #11
Checked plugs and one was a bit loose( 1/8 inch turn) . Fall in Ohio means it was not cold this am to check it out for sure, seemed to run better though. They say it will be cold tomorrow so we will see.
 

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Discussion Starter #12
Still sputtered so I moved the #2 coil pack to #1 . All is good so far I am going to Assume for now it was a bad connection on the #2 coil pack.
 

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Discussion Starter #13
I was able to get it to stutter and the coil pack move made no difference in the code. My local shop guy thinks it could be a crank shaft position sensor. I did have a few crank and no starts in the last few months.
 

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Discussion Starter #14 (Edited)
moved plug from #2 to #1 will see seems to be running much better now. I noticed when I moved plug the never size is gone from the threads. only put a small dab... none the less it is gone. that could be the issue. no issue on last two cold starts.
 

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Discussion Starter #15
the missing is back along with the Ohio cold weather. It is not the change over valve, nor the crank position sensor. I am next trying a set of hotter NGK plugs with a gap of .32
 

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So Tucker is back to running normally. I think the MMO did it's magic. However, the engine is also back to what is has been doing for most of it's life, and stumbling in the cold. It's not as bad as yours SmartDigger, as it never wants to throw codes.

It's whatever, it works fine once it warms up...no big deal to me anymore since I no longer depend on the 451 for work.
 

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Discussion Starter #17
I am trying a new hotter plug. ordered a set of NGK plugs with a gap of .32. It did not start to stumble untill I put the new Denso plugs in that are gapped at .37
 

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Discussion Starter #19
That is my suspicion is wrong plugs. The new plugs cam in Early and I was a happy camper until iI checked the plugs and 1 of the three was a wrong plug. sent them back and now waiting on new order
 

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I wish you the best on this Smartdigger, but everytime I read posts about rough idling especially in colder weather, I feel in my heart of hearts you're gonna end up finding it's a burned valve. You're trying every little thing you can, and I did the same thing. The first thing I did was replace the plugs. I had just bought the car and 4 days later started getting the PO303 code. I was short on money because I just had made the downpayment. So I went to Auto Zone and bought cheap $6.99 auto lite plugs and put in it. Fast forward, the car ended up at a Smart Center and the first thing they said was I put the wrong plugs in it, cheap autolites, how could you? These plugs had less than 200 milies on them at that point. So they put the all key Denso plugs in it and 3 miles for the Smart Center it was throwing the same P0303 code. So maybe it wasn't the plugs huh. Maybe those cheap autolites wouldn't last as long as Denso, but if they were bad for your car they wouldn't mak'em. I switched plugs and coils and Marvel Mystery Oil but the miss was still there. For me the compression test was the writing on the wall for me. I could change the windshield wipers and fill up with a tank of airplane fuel of I wanted, but I had a burned valve, and nothing was gonna cure Max but a complete head job. When you only have 3 cylinders pulling your little car around, there is no extra power to spare. You notice a miss if a cylinder isn't doing it's job properly. The Sam does it's job very well. It sits there and reads the voltage draw on thise coil packs and when that cylinder misfires it say "Oh no" and pops on that CEL. DCO
 
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