I got a 08 2.2 ls that I recently did some engine work on. It all started from attempting to replace water pump and noticing balance shaft chain had slack. Removed timing cover and found the chain tensioner guide broke off but the main chain still intact just skipped a link or two. Ordered a complete kit with new guides chains and tensioners for both. I decided to remove the cylinder head to check valves and none was bent and pistons looked ok. Went ahead a removed all valves and lapped them just to be sure no leakage. Replaced head gasket and all bolts. Goteverything put back together and timing marks lined up correctly started it up and got a p0300 code and it sounded a little off. Took valve cover off and noticed the chain marks didn’t line up with cams anymore. Did the process all over again and made sure tensioners engaged and chain felt tight no slack started it up same thing. What is that happening? Any help would be appreciated. Thanks

 

P0300 is a code for a random misfire detected

https://www.obd-codes.com/p0300

Possibly a ground wire loose, fuel injector connection or spark plug coil connection

Also a possible burnt exhaust valve, doubtful if just lapped in the valves

 

The marks on the timing chain line up properly ONLY when you install it the first time.

Once the engine has ran, the marks move and you would have to turn it over lots of times to get it to the one time it lines up again.

Steve

 

Correction: P0300 mean "misfire detected".. Leave the "random" out.
It means that the crankshaft is not turning at a regular rate, as if there was a misfire but no reliable information to narrow it down to which cylinder.

Did you forget to hook any sensors up? Did you remove the fuse box? Did you remove the ECM?
Check all connections and wires that might have been disturbed. Especially the Crankshaft Sensor and the Camshaft Position Sensor.
Any leakage around the injectors? Did you replace the cups and seals?
Are you using ACDelco 41-103 plugs? The ONLY plugs you should use.
Anything you thought was irrelevant?

 

No correction required, the code is about a random misfire, not a specific cylinder

 

Not exactly; it is about an irregularity in the rotation of the crankshaft. A misfire is detected by the crankshaft sensor the specific cylinder is detected by the camshaft sensor. The position of the camshaft when the crankshaft slows pinpoints the cylinder. "Misfire" does not mean misfire, it means a sensed stumble. This is why the crankshaft sensor variation should be relearned with a new sensor or ECM, even if there is no code.
So, any time the crankshaft is irregular to a degree that damage to the cat is possible a P0300 is triggered. Could be bad sensor data, could be an actual misfire. "Misfire" can be caused by injectors, spark, fuel supply, air supply or gas expulsion. I.E.: injectors, valves, timing, exhaust system, air intake system, plugs, coils, wires etc.
Lapping the valves might be the problem. Do a compression test.
Beware of internet cut and paste, dumbed down, generic explanations. They make the mistake of reading the title and defining it literally instead of doing research.

 

Alrighty then. You saying I just cut and paste?

 

can you elaborate a little more about this? So once I get the marks set with the crankshaft TdC and let’s say I run the engine for a little while and take the valve cover off it’s normal to see the marks not lining up ?

 

That’s correct, if the timing marks are misaligned you would get a P0016 code

 

One would have to count the cogs on all 3 sprockets, count the links in the chain, and do some math to determine how many crankshaft revolutions until all 3 marks realign. And you'd have no way of knowing how far into this cycle it would be when you turned the engine off.