99 Mustang Running Rich

[Bradley t]

Ok so I recently purchased a 99 mustang v6 auto for my daughter for what I thought was a good price til I tried to smog it. I live in CA and shop said I have very high levels of hydrocarbons (gas I believe) said to pass have to b under 51 @25mph considered gross polluter @270 and mine is blowing over 1100!! The car is definitely not running right tech told me to start by cleaning MAF and replacing o2 sensors along with tune up... b4 I start throwing money at this thing I wanted to get some input from others ( not impressed with shop as the tech argued with me for several minutes cuz he swears there is no way my car has four cats, which of course it does) N e way does this seem like the right path or is there another possibility... I'd hate to put in new plugs wires ect just to have it all foul out... n e feedback or suggestions r appreciated

 

[yogiboobooranger]

I'm gonna guess an o2 sensor is bad. Is your check engine light on? Have your car hooked up to check for codes. Usually the pre- cat sensor causes the problem you are experiencing and will cause the engine to run rich. Good luck.

 

[Bradley t]

Thanks for the reply... haven't had much time to work on it but here's what I got so far...
Replaced MAF
Replaced spark plugs with Motorcraft
Replaced plug wires
Old plugs had noticeable carbon buildup
Compression tested 175-195
No CEL no DTC using OBDII scanner
Still smell gas out tail pipes
Gonna try to work some this weekend thinking next step is fuel pressure/injector leak down check and replace precat o2 sensors. I have a similar post on another forum and has steered toward electrical problem... n e one here have any input b 4 I start wrenching please let me know

 

[Bradley t]

Guess I should also mention window wipers/washer not working and sporadic temp Guage readings as well as a hack job of a radio install... but all other GEM functions seem to work... tho still can't c how that would affect my air fuel ratio

 

[BrothersPerformance]

Get a hold of a scanner that can show you exactly what the oxygen sensors are doing. You want to be able to check the short term/long term fuel trims. It's possible you may have an oxygen sensor going out. Make note of what the coolant temperature sensor is reading. The sensor may be failing and telling the computer that it's colder than it is. In open loop the computer adds more fuel to help the engine warm up faster and then enter closed loop.

You can do a noid light test to see if maybe you have a stuck open injector.

 

[Bradley t]

Thanks for the info, I had not thought of the temp affecting fuel ratio, it does read as cold, not all the way at the bottom, but way colder than it should even after driving several miles... so I will add temp sensor/sending unit replacement to the list... not sure I can snag a star scan tool so will just replace first two o2 sensors
Thanks for the quick response

 

[84Ttop]

Get a hold of a scanner that can show you exactly what the oxygen sensors are doing. You want to be able to check the short term/long term fuel trims. It's possible you may have an oxygen sensor going out. Make note of what the coolant temperature sensor is reading. The sensor may be failing and telling the computer that it's colder than it is. In open loop the computer adds more fuel to help the engine warm up faster and then enter closed loop.

You can do a noid light test to see if maybe you have a stuck open injector.

This ^^^ Exactly