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I have a 2008 smart fortwo with a little over 120,000 miles. Recently, I received the P0300, P0302, P0303 codes. It idles and runs rough and has noticeably lost power. I replaced the battery yesterday and the ignition coil on cylinder 2 just the other day. I had begun to suspect the CPS but don't have a code showing that is bad. Any thoughts or suggestions?
 

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oh dear... I was afraid of that. smart center only, I presume?
No, you can do it yourself or have a "competent" mechanic do it for you (good luck finding one :()

It "could" be spark plugs, COP or head gasket....a leak down and compression test will reveal a lot.
 

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Thanks for the insights! I did put in 3 fresh sparks plugs a week ago. The old ones were way improperly gapped! The trouble did start after that, and after driving through a very large puddle on my way to work. I will replace the CPS and if that fails, do the compression and leak down tests. A friend of mine is a mechanic.
 

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If the problem started after the spark plug change, I'd sure start there before throwing parts and money at it. Did you use the correct recommended spark plug or did you fall for the advertising hype some spark plug manufacturers put out? :) Lots of issues with poor running on some Mercedes models when the wrong supposedly better plug is installed.

Len
 

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Sokoloff...yes I used the Bosch replacement plug for the change. Additional information:


1. Problem really started after driving through heavy standing water on the road.
2. when coming to a stop, it cant seem to find the throttle... if I drop it into neutral and rev the gas, it stays running decently.
3. At speed, it seems to run just fine.
4. Car wont stall out, however, if I don't take the actions in #2 , when I press the gas to go, it sputters and has a hard time coming up to speed.
5. Even when running, a slight vibration occurs randomly... like the engine isn't running quite as smoothly as it should or used to.


Thanks again, all!
 

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Well, after changing out the Crankshaft position sensor, unplugging the battery before I even did it, hooked everything back up and its even WORSE! Pulled plugs on 2 and 3 and they are already burned on the electrode. Not wet or oily, just burned. Tried to start it this morning, it barely ran. Have to find a repair person local to Ocala Florida to get it towed to. It spat and sputtered and shook so badly, I barely backed out of my parking space and back in...died 3 times during that process.


UGH!!
 

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My 2 cents but I've never had any success with Bosch plugs or sensors. Japanese engines in my experience like NGK plugs. I've tried other brands and I've had problem with miss firing, fouling, and not seating properly.
 

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buy a set of OEM plugs, gap them correctly, pull apart every electrical connector you can find near the rear of the car, blow the water out of them, use dielectric grease when you reconnect them.
 

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Recently, the BB was idling poorly. It is no where near the mileage required for plugs. Denso irridium plugs were being used. I replaced them with NGK irridium platinum plugs- PLKR7A. Rough idle is gone, it feels like a different car.
As recommended by Brabus007, it might be worth going back to a standard copper core NGK plug and forget the fancy expensive version until you discover what's going on.
 

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driving to work today, in light rain, got the dreaded P0303 code and lost a cylinder. First time the CEL came on, there was no code, and restarting the car made the light go out. after a few minutes, it came back on and got the 303 code. I got it back home (about 20 miles) by resetting the code and driving until it came back on. I found if you stay at lower speeds and in 4th gear, it went further. 5th gear and 55 mph would cause the light and code to pop up sooner.

It has been idling a little rough, and using a bit more fuel than normal. Last plug change, about 15K miles ago, I did use Densos instead of the usual NGKs so gonna try a set of NGK's in the morning when things cool down and the rain stops.

I did try some injector cleaner a few tanks back, and some MMO last tank. Fresh gas less than 20 miles ago, same place I usually get fuel.

Plugs are ordered, be in by 11 tomorrow.
 
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