Hey guys, new here...


Just bought a 400 dollar 05 cobalt to put into daily service so i can semi retire my current DD, an 87 Ranger, and my F250 is to expensive to run at 10mpg and 5/gal gas...lol..

Its an 05 4dr automatic with a 2.2

Anyways....when the engine is cold i get a rapid, popcorn missfire even if i just rev it in park. If i *ease* into the pedal its a 50/50 shot if itll do it, but if i stab it it sounds like a machine gun.


Kicker is once it gets up to around operating temp it runs like new.


I did pull codes, and i got the following...


PO480-Cooling fan circuit 1 malfunction

PO1516- Throttle control actuator performance

PO327- Knock sensor low input

PO341- Cam sensor circuit A performance

PO300- Random cylinder misfire detected


Oddly enough if i clear the codes when the engines warm they dont come back untill it sits overnight and i cold start it. Im pretty mechanically inclined but most my expereince in fuel injection is pre 97 EEC IV ford Truck stuff.


From what ive been reading it seems alot of it points to possibly..


A- A ground wire

B- Knock sensor harness burnt up or corroded

C- The ignition module.


Id be quick to blame the module if it only happend when warm...cause that seems to be when those kind of things get funky, and i would think a wireing issue would present itself regardless of engine temp.


The car does have 220k on it but runs like a champ and doesnt smoke so my gut says internally things are fine.

It also fires right up when cold with no excessive cranking or other nonsense. And is pretty smooth at cold idle except for a miss every now and again.

Can anyone point me in a direction? I do have new plugs and boots to put in. But past that can anyone give some insight before i just start shotgunning parts at it?

 

Well i cleaned the G101 (i think thats the number, the ground under the coolant bottle), the ground on strut tower looked good, but couldnt find the 3rd ground on the subframe? Is it on the passenger side?

Still isnt running right though....got plugs and boots to do today. I noticed the TB says GM so i assume its original....cant tell if the ICM and coil are though.