99 Cougar codes? P0420 P1151 P0171 P0174 All Related?????????????????????????????????

[chubbygoatboy]

I have a 99 Cougar with 4 codes showing.

P0420- Bank 1 Catalyst Efficiency Below Threshold
P1151- Manufacturer Control Fuel Air Metering
P0171- Bank 1 system too lean
P0174- Bank 2 System too lean

The car runs fine. Is there one item in particular that could cause all 4 of these codes? I have seen things related to these codes from intake leak, too much fuel, cat converter, EGR.....too many things possible. So, is there one particular thing that might cause these? Any help is greatly appreciated!!

[mikecox1]

your intake gaskets are bad. i don't care what anyone says i went through the same thing and this will fix your problem. if you plan to do this yourself make sure you replace the upper and lower plentum gaskets

[chubbygoatboy]

Cool, I appreciate the info. After some other reading I had done, I was afraid that might be it. THANKS for the info!!

[chubbygoatboy]

Well, I replaced the upper and lower gaskets. Cleaned out the intake runners. They were heavily crudded up. Also, where the EGR port bolts on to the upper plenum, and goes into the plenum, those passages were completely plugged. It took a while, but I got them cleaned out with lots of carb cleaner and a wire. THE CODES HAVE NOT COME BACK!! THANKS FOR THE HELP!! I hope this helps someone else also!

[chubbygoatboy]

Spoke too soon. The P1151 & P0174 codes are back??? Anybody got any other ideas?? THANKS

[ikaika3383]

Yeah you might want to take a look at the air/fuel meter ( or mass air flow sensor) for contamination. If it is contaminated it will not read the volume of air entering the intake correctly. Also if you can check the wave length of the O2s. If the sensor is bad or shorted it will also send false signals to the computer causing it to run lean against its own will. Oh and yes these codes are related. Good Luck

[Stevo2]

Some good reading...

http://v8sho.com/SHO/TSB982310MassAi...tamination.htm