For a while now I've noticed my long term fuel trims are split at idle and whenever I let off the gas. One side is usually around -13% and the other is -3% approximately, but when I'm crusing they stay pretty consistent with each other and don't vary a whole lot in the other cells.

I also checked my MAP reading and it was 10 vs. the Barometric Pressure which was 30. That indicates no vacuum leak correct?

I've also noticed some oil on the underside of my car near the tranny and stuff which would indicate the intake manifold is leaking. Sure enough I felt the back of the intake and there seems to be a little bit of oil. Do you think this is causing my split LTtrims at idle/deceleration? Thanks.

 

ttt

 

EviLBoX, did you ever resolve this? I've got similar symptoms....BLM is ~128/140 only on closed TPS. I can't find any "external" vacuum leaks anywhere and there isn't an exhaust leak on the passenger side.

I was thinking that maybe the intake manifold wasn't sealing to the heads the way it should be.

Thanks,
Rob
95Z28

 

I still haven't found a resolution for my split LTtrims at idle. I think I'm just going to wait until I do a cam swap and replace the intake manifold gasket, maybe that will fix it if that's the problem. My car has been running fine though, so I'm not too concerned with it.

 

Mine was running great for the first hundred or so miles (new 383). Then, out of the blue, the idle BLM showed up. I'm convinced it's something mechanical gone wrong (i.e. not a programming issue).

Rob
95Z28

 

do you have any oil in the combustion chambers( more than usual) I have the same problems with the long term fuel correction, but I think it's a leak where the head and the intake seal to each other,well on mine I have way too much oil on the spark plugs( checked the valve guide seals , were ok)so I think that the leak is sucking oil from the lifter valley into the intake runner's in the head,and the oil is not letting all the fuel burn , so the blm's , are differnt on the side where the leaks are, and I will change the intake gaskets this weekend then I will see if the blm's change after a few miles of driving

 

My plugs are nice and dry and I don't get any smoke, so I don't think I have an oil-burning problem. However, if the intake isn't sealed to the heads well then I could be pulling air from the crankcase under high vacuum.....that was my thought. Heck, I could be sucking some small amount of oil through there for all I know. Anyway, let me know if swapping out the gaskets works for you!

Rob
95Z28