P0300 - Misfire

4 posts in this topic

Hello all;

New to the Smart car world and I got a code that I am trying to diagnose and solve. Pick up a 06 CDI with 130k. Don't have any history but looks to be in decent shape.

The issue is the check engine light is on with a P0300 code - misfire.


Did the fuel filter, cleaned the EGR that didn't need cleaning, run diesel additives to help clear the injectors. No change

Had the injectors tested and they failed so replaced them with Bosh reman. Made a very noticeable improvement in power and it seems to run well. 
It still throws the P0300 coded after running for a short bit and seems to throw at idle.

Replaced the Crank Position sensor, in hopes but no change.

No smoke, runs well.


Where else should I start looking to diagnose?  What logic or system would throw a P0300?



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Check timing chain and measure cylinder compression. Continue using injector cleaner. 

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Still throwing the P0300 code and with our cold weather, hard to start below -2 deg C.

Had the local diesel shop run a compression test as i don't have the adapters.

1 - 290psi

2 - 275psi

3 - 200psi  The shop said they dropped some oil into #3 and it did not change the reading. 


It has 135km, Based on the reading, seems i have leaking valves. I wish the shop diagnosed a bit more to determine if indeed the compression was low.

Looks like I have a head to rebuild.

Is it worth it? How do the rings fair in a 135km motor?




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It'd be cheaper to get a good running engine from a wrecker.

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