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2009 with P0302 Codes

7950 Views 4 Replies 3 Participants Last post by  BaconBoyCamper
First time poster here, so please bear with me. Some mechanical understanding, enough to make me dangerous. LOL
I have a 2009 Smart, regular engine from what I’m told. Started having multiple codes for misfire on all cylinders. Smarty never had the plugs changed, currently at 150K+ kilometers. Took it to my licensed mechanic, he’s not familiar with Smart Cars but was willing to have a go at it. Changed all of the spark plugs, and checked coil resistances which pretty well matched each other. Things were OK for about a week, then started getting P0302 #2 misfire codes again – only P0302; nothing on the other 2 cylinders. Yesterday, mechanic swapped out #2 coil with #3 , changed out the #2 spark plug again just in case. Out the shop door, but on drive home got the P0302 code again. And many more since, but only P0302.
Also, to add to this, the system two months ago started going into OL Open Loop (OL-FAULT then to OL-DRIVE), which I can reset by turning the engine off and then restarting – this will happen with and without a P0302 code.
For the #2 cylinder misfire, it initially started happening while going uphill for a prolonged period, but will now code at level driving, stop and go traffic. In addition to the OL Open Loop at times.
Seeing that the plug has been changed (twice) and the coil swapped, I’m thinking along the lines of it’s the #2 injector, but my mechanic says that injectors nowadays are fairly reliable. I’ve just put in half a can of Seafoam fuel conditioner into the fuel tank in the hopes that this may free up any injector problems while mechanic is researching.
Anyone with any ideas?
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Welcome to SCoA! :)

Having experienced this same thing on our 2011, my guess is a burned valve in the #2 cylinder. If your mechanic does a leak down check on each cylinder he can confirm this (or rule it out if it turns out to be something electronic....)
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Oooh, not what I wanted to hear -- about the valve. Will keep looking at the electronics in the meantime. I told my mechanic I'll do some research as well and get back to him later this week/early next week. Thanks for the quick feedback!
resistance check is not a bad test, but probably not a complete test on the coils. My 2009 had the same thing for about a year, and I played with coils and plugs until I did a simple compression test. Cyl #2 came up at 35 PSI, the others were 160. I sold the car to a fellow who had plans for a Haybusa smart. I wasn't going to mess with a motor rebuild or a swap.
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Thanks for the info. One of the things that I'll have my mechanic do next week. But for me it seems strange, the problem is intermittent, albeit, continuously happening. Compression / leak down test is simple enough for him to do. Not really feeling hopeful right now, I'm like you, replacing engine probably not in the cards at 151,000 kilometers. Sad, really like our Smarty, still hoping...
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