Posted this in valve cover thread with no luck....let's try a different way.... I have 2 leaking O rings on bank 1. Wondering if this might cause unmetered air to enter and cause 14% long term fuel trim? Recent monkeying around the area while installing new axle boots and clutch/flywheel service so it is possible that I created a vacuum leak, but I can't see anything obvious?
I mean the crankcase is part of the pcv system but highly unlikely this is the cause of your fuel trim problem. If it's 14% on both banks it could be a vacuum leak at the throttle bodies, low maf output or fuel pressure. If fuel trims are split it's more likely an exhaust leak or something allowing air to enter the system pre o2 sensor. (or o2 failing)
My gut thought it was not the O rings, but AI was giving conflicting info. Bank 2 readings are great, so I can eliminate MAF (I have a 5.2) and fuel. Exhaust was removed for my recent work, so that would be the first suspect? OBD scans show no codes thrown, so can i discount O2 sensor?
Well you can’t discount/eliminate anything until it’s fixed. You could swap sensors bank to bank but I suspect you may find the same result.
If you have a leak in the exhaust before the pre cat O2 sensor the fuel trim should continue to increase until it throws a cel because adding fuel will not lower the O2 in the exhaust in that case. If LT is stable then chances are it's on the intake side or injector related.
Yes, LT is very stable at 14. Bought a smoke test machine being delivered today. To mention: Car is running great, and fuel trims were near zero before I did my clutch and axle boots.
You can end up with a positive stable fuel trim with an exhaust leak, it just depends on how bad it is.
I found an innocuous leak at the Y pipe that is forward of the MAF. I thought that the clamp might have created a pin hole, but I could see the pipe was not properly seated on the MAF. Leak is gone. Can a very small leak be significant enough to alter fuel trim? Also, the leak was on the right side, but only bank 1 showed higher fuel trim; since that pipe is shared wouldn't I see the same reading from bank to bank? Or, since the leak was again on the right side would that affect only bank 1. Will do some additional testing and perhaps swap O2 sensors. To mention: -car is running great -bank 2 readings are spot on -new fuel and air filters
I'd like to, but right plenum tube is off and I want to smoke test a bit more on bank 1, along with sending some smoke in thru the exhaust pipe. It would be nice if this little leak was the culprit, but I have to believe there is something else? After that, will button up and drive a bit.
