Hello everyone. Just signed up to the forum... I'm getting a P1174 trouble code (fuel trim cylinder balance bank 1) on my 3.9 that won't clear. There is a somewhat rough idle during warmup, but no other driveabilty issues. I found the engine oil level to be above the high mark and when I drained it recently I noticed it to be 'chocolately' in appearance.

After doing some searching, it seems the most common cause of P1174 seems to be restricted injectors, but because of the oil issue I'm wondering if it's more a problem with the lower intake gaskets which not only are upsetting the air/fuel ratio in one or more cylinders, but also allowing coolant to get into the oil as well.

I was hoping someone might be able to give some guidance as to whether I'm on the right track or not. I know in the past GM had issues with intake gaskets on their other engines, but I thought it had been taken care of by the time the 3.9 was introduced.

Any input is greatly appreciated.

If it helps any, this is a 2008 Chevy Uplander.