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Discussion Starter · #1 · (Edited)
I've read a few post about this code being a misfire but the most difficult one to diagnosis I hope somebody can tell me this isn't timing chain related I know I'm at a 160000 K but I do get a rough idle here and there mainly at start but not really once I'm up and going
Bought the truck for my stepdad he said it should be good for another 40,000 miles always had the oil changed but this has become more pronounced since I just change the oil with Mobil 1.
I figured I would ask here because I have no idea where to look at 1st or fizzes a real simple usual problem with these motors that I can fix easily enough something with the throttle body idle air control Possibly I'm just asking if this code and symptoms is usually timing chain related .

2006 colorado
2.8L
4 cylinder vortec
 

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I'm pretty sure that if you had the infamous head/valve problem you would be getting more than just a P0300 code. Just the code P0300 is not an indication of the timing chain issue.

A vacuum leak can cause a P0300. Check all of the hoses connected to the intake system for deterioration. The two at the rear of the engine are most problematic. Make sure all clamps are secure on the intake. There have also been problems with loose intake manifold mount bolts.

Other possible causes could be low fuel pressure, contaminated fuel, or restricted exhaust.

When were the O2 sensors last replaced? You might try cleaning the throttle body to correct the idle problem.

There aren't any idle control valves on engines with electronic throttle control.
 

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I've read a few post about this code being a misfire but the most difficult one to diagnosis I hope somebody can tell me this isn't timing chain related I know I'm at a 160000 K but I do get a rough idle here and there mainly at start but not really once I'm up and going
Bought the truck for my stepdad he said it should be good for another 40,000 miles always had the oil changed but this has become more pronounced since I just change the oil with Mobil 1.
I figured I would ask here because I have no idea where to look at 1st or fizzes a real simple usual problem with these motors that I can fix easily enough something with the throttle body idle air control Possibly I'm just asking if this code and symptoms is usually timing chain related .

2006 colorado
2.8L
4 cylinder vortec
To build on what has already been stated, adding some easy/basic/cheap things to check:

1. Check battery voltage. If it is lower than 11.5V when the truck is off, consider replacing.
2. Clean throttle body and MAF. Easy work and inexpensive
3. Spark plugs. How are they? Last time they were replaced? Check for oil on the threads. Oil on your spark plug threads could mean your valve cover gasket is shot (they do not seem to last long, mine lasted 70k miles). I was getting random misfires until I got this fixed.
4. Air filter, inspect

If the above items are in check, might need more in depth diagnosis.
 
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