Hey guys,

so I don’t know if anyone’s actually had this happen before but I have a 2010 cobalt ss turbo with a built LDK long block.

been chasing random misfires for some time now. Changed the coil packs, brand new plugs. Got compression/leak down test done & a smoke test the motor passed all those tests.

every time it rains the car starts to misfire I am not sure if it’s some sort of moisture either getting on the MAP/MAF sensors creating this random misfire seems to be only on CYL 1 goes up to 10-13 misfires idling some time. I do have a hole in the driver side fender line and the hole is right beside the SRI, could it be possible that water is going onto the Intake and going through the system getting water/moisture onto a sensor? I also do have a MAF relocate if that matters.

the other day I received a EVAP code, could this be causing theses random misfires? I have never got a CEL from the misfire I am logging them through my interceptor and can clearly hear them happening. Sometimes the car is not even driveable as when I get into boost the car jerks back and forth.

if any one has any idea what it could be please point me in the right direction thanks!

 

Given it only occurs after rain, I'd guess you're dealing with some moisture on the MAF, although I never had a problem with the K&N getting my MAF damp. You could purchase a hydroshield and see if the problem goes away.

Have you tried moving the plug and coil pack from cyl 1 to cyl 2?

I would check your maf and maps for oil build up as a precaution/regular maintenance and clean with a maf cleaner, not saying it is the issue but additional buildup on those sensors are never good.

 

I would check your maf and maps for oil build up as a precaution/regular maintenance and clean with a maf cleaner, not saying it is the issue but additional buildup on those sensors are never good. - this

I can always tell when mine is going to act up by looking at the boost gauge. When the gauge does not return to 20 vacuum on coast, I know its time for a sensor clean. If I leave it, the car will begin to through codes. I take out the top sensor, clean it off, clear any codes, and it is fine for the next 6K. At first, I thought the 3 bar map sensors were going bad. Now I think the Bosch ones are just really sensitive.

 

this is all great information. Thank you guys for your replies. I will purchase a hydro shield & clean both map sensors and the MAF. I still have the stock sensors. What are the benefits of upgrading to the 3 bar map sensor anyways? I’ve always wondered what the point was other than being able to run more boost I believe correct me if I’m wrong

 

yes I have and the misfire continues to be specifically on cyl 1... I know it’s not an engine issue as the car was cleared from all the tests mentioned above. Thank you for your input it really helps

 

It's being able to monitor the boost level better via a higher reading allowing you to verify it's not overshooting, more than running more boost.

 

oh kk cool. I will buy them

 

Sounds like you experiencing the misfire events when you are boosting up under WOT. Do you notice the misfiring under non-WOT driving conditions?

For something like this that you've been struggling with, it's time to pull out the multi-meter and begin checking every wire going to the MAF sensor from end to end between the sensor and the ECU/power/ground. I feel this urge to stop typing because 99% of people won't do this, but this is the type of procedure that is found in the GM factory service manual when diagnosising electrical demons and what the Technicians will do if you give up and drop it off at a shop.