Runs Poor at Startup - Advice?

damacman

Member
Aug 12, 2003
529
0
16
Phoenix, AZ
Like the title says, when I first get in it and start it up (even after it has been running), it runs awful. It kind of sounds like a big - cam car does when it loads up at idle. After a few miles, all appears to be OK. It threw the Service Engine Soon lamp on about a week ago, so I had Auto Zone pull the code - PO133, which refers to the front O2 sensor on the passenger side.

I was unable to verify that the O2 sensor is working accurately, but inspected it the best I could. I looked at numerous similar threads on stangnet, and all have similar symptoms, but different causes. I pulled the IAC and cleaned it out - no difference. Before I reinvent the wheel, any suggestions? Is it as simple as replacing the O2 sensor and calling it done?

2003 5 spd GT
 
UPDATE

Replaced both stock front O2 sensors with Bosch units - problem solved. Interestingly enough, my car idles so smoothly now - I guess this has been an ongoing issue on mine for some time that got progressively worse.

My car has 29k on it - for those with similar problems and similar mods, I'd look here.