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Discussion Starter · #1 ·
So I have an 07 cobalt 2.2 that’s getting misfires on cyl 3 p0303. It also had secondary air injection check valve errors. It shows actual
Misfires on the scan tool, sometimes a few, sometimes over a thousand in 130 miles. I swapped coil packs with other cylinders, no change, replaced plugs with new ac delco iridium, cleaned and moved fuel injectors to different positions. After the injector cleaning it was ok for 300 miles and came back. Changed MAF sensor, changed upper O2 sensor. It will randomly come and go with no reason. Cleaned all connections on injectors and coil packs, checked for bare wires, checked and cleaned connection to injector harness, changed check valve. Any ideas where to go next?
 

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I tried to originally but can’t find a long enough solid extension for my compression gauge to get it down in the spark plug well and tighten. Any ideas for this?
 

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Your local parts house such as AutoZone will lone you acompression gauge set that. Will work.. new / if you don’t. Return it is $40 and change. It could save you $100s in parts and time.

get the basic engine condition understood. No compression..no power system reads misfire.
you’ve already played musical chairs on some parts.
Stop guessing ….do the basics
Does the engine have compression?
Then does the cylinder have spark?
Then does it have fuel?
You may change the order of the tests but until you answer All 3…..your spinning your wheels and not addressing YOUR problems
 

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So I have an 07 cobalt 2.2 that’s getting misfires on cyl 3 p0303. It also had secondary air injection check valve errors. It shows actual
Misfires on the scan tool, sometimes a few, sometimes over a thousand in 130 miles. I swapped coil packs with other cylinders, no change, replaced plugs with new ac delco iridium, cleaned and moved fuel injectors to different positions. After the injector cleaning it was ok for 300 miles and came back. Changed MAF sensor, changed upper O2 sensor. It will randomly come and go with no reason. Cleaned all connections on injectors and coil packs, checked for bare wires, checked and cleaned connection to injector harness, changed check valve. Any ideas where to go next?
I have this same vehicle...5 speed and same issue. Changed plugs (81,000miles) changed #3 injector. Moved coils around...no change. Now have p0203 code...did find broken wire in the fuel injector harness. Have this coming and to install. Hopefully no other issues.
 

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Save your self a bunch of. Time and do a compression and see if cylinder 3 is noticeably lower than the other 3 cylinders
Have installed new fuel injector harness. And...did compression check on 3. Nothing! Appreciate your suggestion...but... Re-manuf engine on it's way. Will be guaranteed 3yr/100,00 miles. What a bummer...It's more man hours to tear down, fix valves, piston, etc. I have tools, but not everything needed...cherry picker. So shop will get this done. I have heard this sometimes happens around the miles I have on car..81,000. Hey...it's 15 years old and other wise runs great and I love it. Beats buying a new/use car, which are priced out of the market...then sales tax, etc. So now I won't even have car payments.
 

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There is a shop in the Dallas area that has new not reman but brand new 07-08 L61 2.2L for right around $1500. That’s very hard to beat just just for the complete head assembly rings and bearings
 

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There is a shop in the Dallas area that has new not reman but brand new 07-08 L61 2.2L for right around $1500. That’s very hard to beat just just for the complete head assembly rings and bearings
Sounds great, but I'm in St. Louis. Thanks for the info. So, until replacement is done, keep driving my Chevy 94 truck. Still runs great with only 152,000 miles on it.
 
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