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Discussion Starter · #1 · (Edited by Moderator)
I have a chevy Malibu v6 2012 LTZ, it has 120000 miles, i have been struggling for months now to discover what really causes this misfire, the engine shakes when idle, the fuel economy is really bad, it takes time to pickup speed, i started to look in the internet, there lot of talks about oxygen sensor but still every mechanic says that not the case, i have swapped the ignition coil between #2 and #4, still getting #4, i have changed the timing chain cause a lousy mechanic told me that is 1000% sure that what the issue is, but eventually turned out it wasn’t, i have changed all sparking plugs, and new oil, still same issue,

my theory:

since the check engine is only start flashing when rpm below 800 and above 500~, when i turn ac on, the rpm goes up to 900, then the check engine become steady and the esc service lights goes off, same if im driving,
could be that the engine is losing compression? How can i identify that !?

Otherwise what could be the issue !!! Help



Speedometer Car Trip computer Odometer Motor vehicle
 

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2011 Malibu LTZ 3.6L V6 Red Jewel Tintcoat
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What codes do you get when you scan it?

Does the scanner also read all 4 code groups and not just the common P codes, but also B, C, and U?
 

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Compression can be low in a cylinder and miss fires can occur at low rpm and yet fire at higher rpm.
Take it to a dealer, your odds are better there than at Joe Blows garage to get an accurate diagnosis.
 

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2016 Malibu 1LT 1.5T/6-speed 6T40
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I would go the Chevy dealer route. Seeing what you have tried, the code, and isolation to that cylinder, I don't see what else could be cheap and simple to try. The dealer will likely run a wet and dry compression test to isolate rings vs valves if their diagnostic doesn't pull something sensor related. The compression test takes about 15 minutes longer than a simple spark plug change so isn't very expensive. Outside that, you could try talking to the mechanic and negotiating the price down since he botched the timing chain diagnosis... just to compare with the $$$ estimate at the dealer.
 

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I have a chevy Malibu v6 2012 LTZ, it has 120000 miles, i have been struggling for months now to discover what really causes this misfire, the engine shakes when idle, the fuel economy is really bad, it takes time to pickup speed, i started to look in the internet, there lot of talks about oxygen sensor but still every mechanic says that not the case, i have swapped the ignition coil between #2 and #4, still getting #4, i have changed the timing chain cause a lousy mechanic told me that is 1000% sure that what the issue is, but eventually turned out it wasn’t, i have changed all sparking plugs, and new oil, still same issue,

my theory:

since the check engine is only start flashing when rpm below 800 and above 500~, when i turn ac on, the rpm goes up to 900, then the check engine become steady and the esc service lights goes off, same if im driving,
could be that the engine is losing compression? How can i identify that !?

Otherwise what could be the issue !!! Help



View attachment 73157
Check behind heat shield, it could be a crack in the exhaust manifold which is common on these. Replace manifold and gasket and your problem will be gone.
 
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