Hi. I´m new here, and im from Denmark, and i have a problem with a F150 running rich, totally black exhaust when engine light comes on. when engine light is off it runs perfectly clean.

I´ve changed the following : HEGO sensor right side, Spark plugs, ign wires, water temp sensor, resetting ecm, all plugs cleaned, all visible vaccumlines inspected etc.

The only code is this : "173 HEGO sensor circuit indicates system rich (right side)"

Usually the engine light turn on after 1 mile, and then the exhaust is black. sometimes after resetting ecm the light comes on after 100 feet of driving, other times after resetting it can drive like 10 miles without any problems.

The truck is all original except for the cat back single exhaust, that is a little bit modified....(flowmaster)

It starts with no problems, and drives smootly, but is running rich, and likes the gas stations.. ($6.00 pr gallon) not fun at all..

Any solutions ?

Teddy

 

Unplug the vacuum hose from the Fuel Pressure Regulator, and see if there is any fuel in the vacuum hose. If there is, replace the FPR. If there isn't, check the fuel pressure at idle, with and without the vacuum hose attached to the FPR. Note both readings. Allow it to idle for 5-10 minutes, and look for any changes in the pressure reading when it starts to run rich. Finally, watch the gauge after you turn the ignition off, and see how fast the gauge bleeds down. Note all of these things, and post your results here.


Just out of curiosity, is the MAP sensor original?