I didn't mean you in particular. I meant anyone that has been trying to help that says the LAP engine won't work. My fear about changing the ECM is that I'm going to have to swap out more parts. So far most have been interchangeable between the 2 engines but who knows. That's just my luck.

I swapped injectors then replaced them. I also replaced the insulators that snap onto the bottom of the injectors. We did a smoke test and found tiny little puffs of smoke coming out of the insulator of injector #4. There was a little chunk taken out of the o ring on it. I think if there was a crack or leak on cylinder 1 we would have seen it then. At least one would hope, right?

 

Awhile ago, you mentioned a hissing noise, was that tracked down? Could the intake manifold be cracked? Loose? New a new oring? Or a fastener not fastened?

I just reread this whole thread, that seems to be a potential source of the P0301

 

understand. When i get gremlins like that i just recheck basics....fuel, fire and compression all at the right time and amounts....has to work

the engine you have now is a vvt engine right? I would think the basic engine is the same, just the stuff that makes the flex-fuel possible different

 

Yes that was the insulator that was making that noise. As soon as we replaced it the hissing went away.

Yes and it ran fine for about 3 months before the Cat blew a hole and I've been dealing with this code ever since. The original engine was a VVT as well. We pulled the solenoids off of another HHR then checked the part numbers to make sure they were interchangeable between the 2 engines.

I've been using AutoZone's website to cross reference. I look up the part under the HHR then change the car to the Cobalt and make sure everything still says fits your car. The only thing so far that wasn't the same were the injectors.

 

Ohhhh, so i missed the part about it ran fine for 3 months.....then hole in the converter and miss fire before or after another converter?

 

Yeah when the Cat went is when the code kicked. I've replaced everything since with no change.

 

i would say since it ran good for 3 months before the cat issue....got to be related

 

Then could it be on the exhaust side? A gasket leaking, loose exhaust manifold fasteners? Damaged exhaust gasket?

 

Yeah but I've replaced the Cat and both O2 sensors that are in the Cat and the gaskets at either end. But that doesn't mean there isn't a leak.

This weekend after we take it down and try to get some answers, if they can't find the issue I will jack it up and take pictures of the Cat at either end and maybe we can see something that no one else saw.

 

The problem would be between the exhaust manifold and the head. A problem at the manifold to the down pipe wouldn’t trigger a P0301 code.