2011 2.2L ecotec

Back story - brought the car with a blown engine, replace the engine.
New engine was used with 75K miles from a cobalt, did the following before I installed it
1. replace water pump
2. timing chain + gears not the VVT gears, both chains.
3. Thermostat
4. New plugs

I got the recommended items from here, so only the good parts.

When i first started it, it ran rough, i almost thought it was bad timing, but its was one of the cyl not firing. I replaced the used coil packs with the coil packs from the previous engine. All was fine.

Now since that event, it has a the code P0302 stored (PDTC). Engine runs fine.

However the engine light came on the other day with the same code P0302 (DTC), I cleared it from DTC and now today after a 30 min drive it did the same.

I ordered new coil packs and will replace all 4.

However my question is, if the code P0302 is stored in PDTC, even thou i cleared it from DTC, would it cause it to continue to come back until it's clear from permanent storage (PDTC)? or does it only come back if it continues to detect the same issue?

 

To confirm you installed new AC Delco 41-103 iridium spark plugs, reused the coils from your old engine correct?

Try just replacing the #2 coil second from the timing chain side of the engine, the code indicates that cylinder has the issue.
If the same code comes back , swap #2 and #4 spark plugs, see if the code goes away or changes to P0304.
If it does change then it’s that spark plug has an issue.
I recommend you also inspect the coil connector to ensure there are no bent pins in the connectors

https://www.obd-codes.com/p0302

Then if you are still getting P0302 , inspect or replace the fuel injector, you have four spares from your old engine.

 

Thx will be trying that.

 

If you're going to be pulling plugs and swapping them around, you should do a compression test while you're at it.

 

Yes, it could be a dead cylinder, can’t hurt to check it out.

 

Stored it doesn't mean aything except that it has happened before the CEL comes on if it is current (happened recently) if it doesn't happen again in a bunch of cold srtarts the CEL will go out and the code will once again be stored. A stored code will clear after a bunch of cold starts. (a "bunch" is variable usually around 100)

 

Car doesnt feel any different. A dead cyl would cause the engine to vibrate a lot or not run correctly.

 

Correct but a compression test is still a good way to confirm engine condition, which the yard should have tested prior to selling it to you.
You’re right a dead cylinder would cause a rough idle, a bad vibration when applying throttle.
so, switch the plugs and tgen the injector if required, it’s just a way to test and confirm the problem.

 

Bringing this conversion back.

So the issue continues but its not consistent, sometimes it runs fine for 2-3 days then all of sudden the light comes on and the engine runs a little rough, after turning off the car and back on it runs fine for a while. Compression is normal.

Here what i replaced/have done so far

1. new plugs
2. new packs
3. Axle speed sensor
4. #2 fuel injector
5. MAF sensor
6. Both VVT Solenoids
7. new battery

What else is there to try? I still think this is a sensor as the issue is not consistent.

 

Compression test was mentioned several times. Have you done that ? Or are you just throwing more parts at it without doing any diagnostics.