Constant misfire code after engine swap

I am in a bit of a bind and I was hoping someone here might be able to help me out. My shop did an engine swap for a good friend of my in his 05 Aveo with the engine from an 07. Everything went great, with the exception that check engine light flashes and it sets a constant P0300 random misfire code.


There is no misfire, the new engine runs great. Of course the problem is that this code prevents the car from going into overdrive. At first we had someone with a Tech-2 come out to do a CKP relearn, and that seemed to fix the problem, but only for a few days. After that the problem came back. It will set the code like clockwork as soon as the car hits 3^rd gear.


We have exhausted every possibility we can think of (we have even done the CKP relearn several more times.) Again, there is no actual miss. It only thinks there is.


Anyone have any suggestions?

did they install new wires and or spark plugs?

Yes, plugs and wires are new, and the P0300 code is the only one being set.



Are there any known incompatibilities between the 05 computer and the 07 engine?

there are a few differences. But are your accessories (parts bolted on to engine) from the 05 or 07? which harness did you use?

i am not sure about specific signal differences of signal outputs of sensors or anything between the years. But my honest suggestion would be give more specific information about the swap. It could be a misfire by lack of fuel, if you put in a junk yard engine, and used the injectors from the junk yard, they might be clogged from dried out gas from it sitting..

Possibiliity of a shorting coil or bad connection at the coil?

I need to stress that this is NOT a miss. It is an ingition miss. It is not a fuel miss. It is not a miss of any sort. It is not a problem with the plugs, wires, coil, injectors or anything. The engine runs perfectly. It only THINKS it is missing.

We swapped in the 07 engine using all of the accessories that were already in the car. Now part of the problem is that while the car is an 05, I am not sure the engine that came of it was. Someone had swapped it before, and we have no way know knowing what they may have done.

So the best I can figure one of two things is happening, either their is some sort of imcompadability between the 05 ECM and the 07 Engine, or something in the engine (valves?) is ever so slightly worn and causing it to throw a P0300. I know there is a TSB about that last option, but I sure hope that is not the case when the engine only has 70,000 on it.

Now are there any common issues when swapping these engines that can force the computer into limp mode when there is no true miss?

You need to go have a 'crankshaft relearn procedure' done by a dealer or something with a fancy OBDII tool. I had the same problem when I swapped the 07 engine into my 05. I ended up having to go to the dealer and they took care of it for 1hr of labor. That fixed it.

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Originally Posted by Daox

You need to go have a 'crankshaft relearn procedure' done by a dealer or something with a fancy OBDII tool. I had the same problem when I swapped the 07 engine into my 05. I ended up having to go to the dealer and they took care of it for 1hr of labor. That fixed it.

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If you look back to my first post I explain that I have had this done a number of times. It never fixes the problem.

The first shop that tried it had problems with it too with a tech-2. For some reason the dealer got it to work right.

Quote:

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Originally Posted by Daox

The first shop that tried it had problems with it too with a tech-2. For some reason the dealer got it to work right.

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Did the first shop get it to relean at all? I have had two guys relearn it, both times the relearn was successful, but neither fixed the problem.

I'm not absolutely sure what happened. If I had to guess I'd say it failed because they said they couldn't do it, but the dealer could.

Quote:

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Originally Posted by Daox

I'm not absolutely sure what happened. If I had to guess I'd say it failed because they said they couldn't do it, but the dealer could.

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Thanks, but unfortunately this does not help me much. The relearning process does not fail for us, it just does not fix the problem.

change out your spark plugs for ngk coppers