Running Rich

[87MK111Supra]

I have an interesting equation here. The car is originally a CA car but the engine is one of those out of a Cressida from Japan. I rebuilt the engine 50k ago and put all the CA smog stuff on it so it would pass visual. It kept throwing a code saying EGR but I replaced everything twice and couldn't figure it out. I swapped ECUs for a nonCA one and that fixed the light problem. Everything has been running smoothly until recently when the car runs noticeably rich, I can smell it at stoplights sometimes. The deposits are blackening the back of the car after a couple months. The O2 sensor has recently been replaced (last 10k) but was a nonCA O2 sensor. I was reading and found that the AFM could be the cause? would a loose connection cause this as well? Any other problem areas I should pay attention to? THe car has 265k on it and 50 k on the engine.

 

[Nick M]

Perhaps you have an exhaust leak upstream from the oxygen sensor. That would cause it to read lean, when it isn't. And as such, the computer will richen the mixture. The AFM can do it, if you open it up and loosen the clock spring. (Don't do it)

 

[87MK111Supra]

Would a manifold leak cause this? or are you thinking crack?

 

[Nick M]

A crack in a manifold is a leak. The likely place would be the elbow/elbow gasket. It has to effect the sensor, if that is what is going on. What codes are stored?

 

[87MK111Supra]

Ya I know that. I'm not getting any codes, will check the gaskets tomorrow and see how everything is. I have a feeling the manifold to port gasket isn't sealing properly.

 

[Nick M]

When the exhaust manifold gasket leaks, you can usually hear a put-put-put sound at idle. It isn't very loud.