85 2.6l 4x4 failed smog

[Kneepuck]

Hi all,

My 85 failed smog. On the first try;
co2 14.40 o2 0.67 hc 61 co 0.20 no 1135 at 15mph
co2 14.40 o2 0.66 hc 57 co 0.20 no 1052 at 25mph

On inspection of the Mikuni carb, I found a leaky fuel pump, which explained the smell of gas all the time, as well as non-working accelerator pump. The truck would stumble on acceleration when warm or cold but ran ok otherwise..

After repair:

co2 14.02 o2 0.84 hc 51 co 0.22 no 1536 at 15mph
co2 13.86 o2 0.72 hc 43 co 0.27 no 1317 at 25mph

Now runs well but still failed


Any suggestions?

Thanks in advance

[geezer101]

Looks like the usual suspect in this problem - the EGR valve and gallery are fouled up. If the exhaust gas recirculation isn't operating properly it will mess with the gas readings.

[Kneepuck]

Ok, thanks for the info. That will be next on my hit parade.