So I popped on some AFR heads this past weekend (That was a project with a whole slew of adventures... holy hell) and bank 2 is reading lean as hell at idle and when im coasting. My tailpipe is filled with soot. Something is wrong here and I have no clue how to find it. Are there any tricks to finding a vacuum leak? I don't mind bumps in the road... but this **** is old now.

 

carb cleaner or brake cleaner, spray around the intake and listen for the engine to rev-up

 

First off what are we working on here???

Did you replace the intake gaskets or re use the original???

What other problems did you have???

Was there any known problems before you started???

 

It's the 2005 Sierra Denali in my sig. 6.0 LQ9 and the heads are AFR 225's. I'm running the NNBS intake manifold. The heads are used and I got a pretty good deal on them from a buddy. I'm nervous there could be a problem with one of the heads which is why I was hoping to find a way to locate the vacuum leak rather than testing to see if the intake is sealed right. I know testing the intake *could* find it, but it doesnt sound too exact either.

I reused the original intake gaskets, I'm not sure there are any other problems, and there was nothing wrong before I started. I have HPT files I can send you guys if that would help.

Thanks for the replies!

 

Did the gasket's look smooshed down???

The original orange color design had problems with this and they would not seal right. GM changed the material to help with this and to be compatible with E85.

Some time the leak is from the bottom side and spraying carb cleaner around the top won't get down there were the leak is.

also check your exhaust gaskets and make sure you don't have air being sucked in there.

 

If it was on the exhaust side wouldnt I hear it? The intake has blue/green seals on it I believe... didnt look too smooshed to me.

 

Those should be the better seals on the intake. what about the exahust gaskets??? Are the ones on the head factory Steel layered???

 

I got new factory exhaust gaskets. I replaced the gaskets that the ARH came with when I did the head swap. They were fine, but I didnt wanna reuse them because they were pretty pinched down from the original install.

Do you really think I wouldnt hear the leak if it were on the exhaust side? I havent spent any time checking that becuse I couldnt hear anything under mid throttle or better.

 

I would think if it was sever enough that you would hear it. Do a quick look and see if you see any evidence of the exhaust leaking out... you would see the same black soot you mentioned on the tail pipe.

are you sure the 02 sensor is ok??? When you watch it does it cycle or or does it get stuck???

Sorry I don't have HPT so I can't view your log.

Post it up may be some one that does can take a look.

 

I attached 2 logs. The first (6am) was taken right after I tried messing with the intake. I hadnt reset the fuel trims and fuel trim learn was on. For the second log I reset the fuel trims and turned fuel trim learn off. This is on a SD tune to help get it dialed in as best possible.

The O2 readings are weird in the second file, but they seem fine in the first. Better at least...