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Discussion Starter · #1 ·
Hello all,

'13 LTZ 80,800 miles

Here's a short run down of what's been going on for those who don't know the issues I was having.

I had a random p0300 code while driving along one day, at the suggestion of my gm mechanic friend I started monitoring my fuel trims. It didn't take long for me to realize there was a problem as the long term, mostly bank 2 was 14-18, with bank 1 chasing right behind it.

I tried a bunch of things and in the end called a local mechanic who discovered the problem was a vacuum leak at the oil filler tube The "tube" is a black plastic tube about 2" long that your cap screws into and it goes into the engine. To fix this problem all he did was turn it hard and to the right sealing the o ring stopping the vacuum leak.

All is well

Today- due for an oil change. I decided to switch to pennzoil platinum from royal purple because the parts store was out of RP in 5w30, and I had a gift card for that store, plus I always wanted to try it. I also had a can of BG EPR engine flush which everyone seems to rave about, also something I wanted to try.

I added the flush to the crankcase per the directions and let the car idle for 45 minutes. During which time I had my scan tool hooked up looking at different things, going back every so often to check on fuel trims just to make sure they stayed ok, which they did. I then watched the oil drain, and to my surprise some gunk solid type (didn't go fishing in the drain pan for it just saw it drain out) stuff came out. So I was pretty happy that it actually seemed to have done something.

I finished the oil change and took the car for a drive. I still had my scanner hooked up and left it on fuel trims, I happened to glance over and YIKES! Long term bank 1 was 19 bank 2 was 21, this was at a stop sign, they went down slightly when I started to go. Every time I stopped bank 2 would be over 20 and bank 1 would be 18-19. My first thought was the filler tube not sealed well but I did everything I could and still no change, I even took the filler cap and the engine cover off and covered the tube with the palm of my hand and put all my weight down on the car to seal the tube against the engine, I held that for ten full minutes and the numbers didn't change. I then thought that maybe after the engine flush the engine is running a bit different so the fuel trims would somehow need to be relearned, I know that the keep alive memory should relearn after 10 miles of driving, but after 25 it still hadn't improved.

Is it possible the solid gunk I saw coming out of the oil drain was part of a seal that the flush ate away? And now I've got a vacuum leak somewhere else. Or could it have somehow ruined a sensor? BG specifically said their stuff won't do that but crazier things have happened. Or as crazy as this sounds could somehow the oil be messing with the computer in the car? I know that sounds really far fetched, but I've had that oil filler cap on and off half a dozen times since it was fixed without any problems, but as soon as I change the oil everything goes crazy??

I saw another post on here from someone having their evap purge solenoid go bad. Mine makes this god awful ticking noise especially when it's cold. The mechanic who came the other week even said it was the loudest he'd ever heard. It's definitely not the injectors or anything else, you can put your hand on it and feel the tics in sync with hearing them. I wonder if that's a sign it's going bad and part of the problem? Anyone know how to test one?
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