Advice from the group I'm So Confused

[mowfixer]

My 99 OHV has been giving CEL only on very cold mornings. The truck runs smoothly even when cold and I am still gettin 21 MPG. Codes are lean bank 1,2. After reading this forum for a long time I went to check for an intake leak. I sprayed around the manifold when the truck was very cold. When I sprayed the base of the upper plenum I got an immediate change in engine speed. I tried sparying the lower intake area with no change in engine operation.

Here is my question. I do not have time right now to fix it myself even though it is an easy fix. I have taken it to two mechanics I know. One says upper intake gaskets (makes sense to me from symptoms above) and the other says since it is lean on both banks that all I need is an O2 sensor.

Do you guys believe I am right if I have the upper gaskets changed or am I missing something. I do not want to pay for work that is not needed as they want $125 to change gasket.

 

[dogfriend]

I think that your "lean" code is probably caused by the leak you found in upper intake. I would fix that before changing the O2 sensor. It appears that the O2 sensors are working the way they are supposed to because they are detecting a lean condition when you have extra (unmetered) air entering the intake via the leaking gasket.

 

[corkey]

X2 , leak = more air = lean condition = CEL

 

[Brandon96]

x3 - CEL banks 1 aaand 2 (P0171 - P0174), had the same problem, same engine, upper intake gaskets.

 

[my98nnj]

I have taken it to two mechanics I know. One says since it is lean on both banks that all I need is an O2 sensor.

Now you know which mechanic NOT to go to.

BTW - Just to point out how stupid that diagnosis is, if it was lean on BOTH sides, don't you think he'd tell you BOTH o2's are bad, not just one? Makes no sense at all. Don't ever let him do any work on your vehicles.

 

[mowfixer]

Fixed

I went with mechanic 1 and had upper plenum gaskets replaced. Good move as he said old ones were flat and actually recessed in the grooves and not even touching the mating surface.

Thanks all for the advice!

 

[imp]

I went with mechanic 1 and had upper plenum gaskets replaced. Good move as he said old ones were flat and actually recessed in the grooves and not even touching the mating surface.

Thanks all for the advice!

This Forum is worth it's weight in gold (almost....) yes? imp