Codes 172 and 136 still there

[rdodd10]

I have a 93 XLT. I had codes 172 and 136. I replaced both O2 sensors and cleared the codes. After about ten miles, the CEL came back on and the codes are back. Wiring looks good. I am looking for ideas.

 

[MrShorty]

A lean code for both sides suggests looking for things that are shared. Have you checked fuel pressure? Any vacuum leaks? I've heard of a few cases where a bad computer ground contributed to these codes.

 

[rdodd10]

172 and 136 codes

Fuel pressure is good, no vacuum leaks. The engine runs good.

 

[rdodd10]

Possible Vacuum Leak

It is running worse when cold. I think the upper intake is leaking - I am going to test that after work. It also idles slightly high, my clue to intake leak.

 

[rdodd10]

Found It

I found the leak. A really large 90 degree elbow was leaking bad. Did not show up the first time I checked for leaks.

 

[MrShorty]

Glad you found it.

 

[rdodd10]

Codes still there

I fixed the vacuum leak, engine runs as smooth as glass. After ten miles, light came back on and codes are there again. Checked for vacuum leaks, found none including on upper manifold surfaces. ????

 

[rdodd10]

Changing gasket Saturday

I got a new Upper Intake gasket and EGR valve - going to change all on Saturday. The EGR was carboned up, though with tests it showed ok. Will change it anyway.