Po301 and ticking noise

Asked by Nov 04, 2018 at 07:45 AM about the 2007 Chevrolet Cobalt LT Coupe FWD

Question type: Maintenance & Repair

07 cobalt 2.2  suddenly died, was driving fine up to
that point. Battery was replaced along with
alternator a few months before. Changed plugs
finally started with horrible chain slap noise. Only
code was po301 and po171. Replaced timing chain
and components.  Replaced crankshaft tensioner,  
crankshaft chain looked fine. Note: timing chain
was slightly loose but not broken. Then had no
start no crank, found starter was gone replaced ed
starter, starts fine. Makes slight ticking noise, now
code po301 back again and really low on power.
Doing a compression check today but any other

3 Answers


Compression test will likely tell you #1 cylinder is down on compression. This may mean that one of the valves is bent. Just a guess though.

1 people found this helpful.

I did compression test, cyl 1 is 120, the rest is all 150. I continued to hear for tapping ticking noise and I definitely hear it under valve cover. Took it for a drive, no cel on, drove fine except for a little noise. This morning its rough and shaky. Could this be sticking valve, bent valve? Would replacing head cure problem?


If possible have a qualified mechanic evaluate it. It could even be a camshaft / valve lash issue. Pretty hard to figure out sitting behind this monitor.

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